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$I'$I'I$I$I$I$I$I'Inm۶m۶m۶m۶m6n=~mmm= X HELP_DATEThis help information was generated from the MariaDB Knowledge Base on 2 September 2019.`2AREAA synonym for ST_AREA. URL: https://mariadb.com/kb/en/polygon-properties-area/https://mariadb.com/kb/en/polygon-properties-area/U#CENTROIDA synonym for ST_CENTROID. URL: https://mariadb.com/kb/en/centroid/https://mariadb.com/kb/en/centroid/ p:ExteriorRingA synonym for ST_ExteriorRing. URL: https://mariadb.com/kb/en/polygon-properties-exteriorring/https://mariadb.com/kb/en/polygon-properties-exteriorring/ r;InteriorRingNA synonym for ST_InteriorRingN. URL: https://mariadb.com/kb/en/polygon-properties-interiorringn/https://mariadb.com/kb/en/polygon-properties-interiorringn/x>NumInteriorRingsA synonym for ST_NumInteriorRings. URL: https://mariadb.com/kb/en/polygon-properties-numinteriorrings/https://mariadb.com/kb/en/polygon-properties-numinteriorrings/ "ST_AREASyntax ------ ST_Area(poly) Area(poly) Description ----------- Returns as a double-precision number the area of the Polygon value poly, as measured in its spatial reference system. ST_Area() and Area() are synonyms. Examples -------- SET @poly = 'Polygon((0 0,0 3,3 0,0 0),(1 1,1 2,2 1,1 1))'; SELECT Area(GeomFromText(@poly)); +---------------------------+ | Area(GeomFromText(@poly)) | +---------------------------+ | 4 | +---------------------------+ URL: https://mariadb.com/kb/en/st_area/https://mariadb.com/kb/en/st_area/ 6&ST_CENTROIDSyntax ------ ST_Centroid(mpoly) Centroid(mpoly) Description ----------- Returns a point reflecting the mathematical centroid (geometric center) for the MultiPolygon mpoly. The resulting point will not necessarily be on the MultiPolygon. ST_Centroid() and Centroid() are synonyms. Examples -------- SET @poly = ST_GeomFromText('POLYGON((0 0,20 0,20 20,0 20,0 0))'); SELECT ST_AsText(ST_Centroid(@poly)) AS center; +--------------+ | center | +--------------+ | POINT(10 10) | +--------------+ URL: https://mariadb.com/kb/en/st_centroid/https://mariadb.com/kb/en/st_centroid/ w*ST_ExteriorRingSyntax ------ ST_ExteriorRing(poly) ExteriorRing(poly) Description ----------- Returns the exterior ring of the Polygon value poly as a LineString. ST_ExteriorRing() and ExteriorRing() are synonyms. Examples -------- SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))'; SELECT AsText(ExteriorRing(GeomFromText(@poly))); +-------------------------------------------+ | AsText(ExteriorRing(GeomFromText(@poly))) | +-------------------------------------------+ | LINESTRING(0 0,0 3,3 3,3 0,0 0) | +-------------------------------------------+ URL: https://mariadb.com/kb/en/st_exteriorring/https://mariadb.com/kb/en/st_exteriorring/ +ST_InteriorRingNSyntax ------ ST_InteriorRingN(poly,N) InteriorRingN(poly,N) Description ----------- Returns the N-th interior ring for the Polygon value poly as a LineString. Rings are numbered beginning with 1. ST_InteriorRingN() and InteriorRingN() are synonyms. Examples -------- SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))'; SELECT AsText(InteriorRingN(GeomFromText(@poly),1)); +----------------------------------------------+ | AsText(InteriorRingN(GeomFromText(@poly),1)) | +----------------------------------------------+ | LINESTRING(1 1,1 2,2 2,2 1,1 1) | +----------------------------------------------+ URL: https://mariadb.com/kb/en/st_interiorringn/https://mariadb.com/kb/en/st_interiorringn/ .ST_NumInteriorRingsSyntax ------ ST_NumInteriorRings(poly) NumInteriorRings(poly) Description ----------- Returns an integer containing the number of interior rings in the Polygon value poly. Note that according the the OpenGIS standard, a POLYGON should have exactly one ExteriorRing and all other rings should lie within that ExteriorRing and thus be the InteriorRings. Practically, however, some systems, including MariaDB's, permit polygons to have several 'ExteriorRings'. In the case of there being multiple, non-overlapping exterior rings ST_NumInteriorRings() will return 1. ST_NumInteriorRings() and NumInteriorRings() are synonyms. Examples -------- SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))'; SELECT NumInteriorRings(GeomFromText(@poly)); +---------------------------------------+ | NumInteriorRings(GeomFromText(@poly)) | +---------------------------------------+ | 1 | +---------------------------------------+ Non-overlapping 'polygon': SELECT ST_NumInteriorRings(ST_PolyFromText('POLYGON((0 0,10 0,10 10,0 10,0 0), (-1 -1,-5 -1,-5 -5,-1 -5,-1 -1))')) AS NumInteriorRings; +------------------+ | NumInteriorRings | +------------------+ | 1 | +------------------+ URL: https://mariadb.com/kb/en/st_numinteriorrings/https://mariadb.com/kb/en/st_numinteriorrings/ |)WKT DefinitionDescription ----------- The Well-Known Text (WKT) representation of Geometry is designed to exchange geometry data in ASCII form. Examples of the basic geometry types include: Geometry Types | POINT | LINESTRING | POLYGON | MULTIPOINT | MULTILINESTRING | MULTIPOLYGON | GEOMETRYCOLLECTION | GEOMETRY | URL: https://mariadb.com/kb/en/wkt-definition/https://mariadb.com/kb/en/wkt-definition/ W%AsTextA synonym for ST_AsText(). URL: https://mariadb.com/kb/en/wkt-astext/https://mariadb.com/kb/en/wkt-astext/V$AsWKTA synonym for ST_AsText(). URL: https://mariadb.com/kb/en/wkt-aswkt/https://mariadb.com/kb/en/wkt-aswkt/i/GeomCollFromTextA synonym for ST_GeomCollFromText. URL: https://mariadb.com/kb/en/wkt-geomcollfromtext/https://mariadb.com/kb/en/wkt-geomcollfromtext/o5GeometryCollectionFromTextA synonym for ST_GeomCollFromText. URL: https://mariadb.com/kb/en/geometrycollectionfromtext/https://mariadb.com/kb/en/geometrycollectionfromtext/a+GeometryFromTextA synonym for ST_GeomFromText. URL: https://mariadb.com/kb/en/geometryfromtext/https://mariadb.com/kb/en/geometryfromtext/ a+GeomFromTextA synonym for ST_GeomFromText. URL: https://mariadb.com/kb/en/wkt-geomfromtext/https://mariadb.com/kb/en/wkt-geomfromtext/ a+LineFromTextA synonym for ST_LineFromText. URL: https://mariadb.com/kb/en/wkt-linefromtext/https://mariadb.com/kb/en/wkt-linefromtext/c-LineStringFromTextA synonym for ST_LineFromText. URL: https://mariadb.com/kb/en/linestringfromtext/https://mariadb.com/kb/en/linestringfromtext/ (MLineFromTextSyntax ------ MLineFromText(wkt[,srid]) MultiLineStringFromText(wkt[,srid]) Description ----------- Constructs a MULTILINESTRING value using its WKT representation and SRID. MLineFromText() and MultiLineStringFromText() are synonyms. Examples -------- CREATE TABLE gis_multi_line (g MULTILINESTRING); SHOW FIELDS FROM gis_multi_line; INSERT INTO gis_multi_line VALUES (MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')), (MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')), (MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2), Point(3, 5)), LineString(Point(2, 5), Point(5, 8), Point(21, 7)))))); URL: https://mariadb.com/kb/en/mlinefromtext/https://mariadb.com/kb/en/mlinefromtext/x(\F Lu A7oy m`)MPointFromTextSyntax ------ MPointFromText(wkt[,srid]) MultiPointFromText(wkt[,srid]) Description ----------- Constructs a MULTIPOINT value using its WKT representation and SRID. MPointFromText() and MultiPointFromText() are synonyms. Examples -------- CREATE TABLE gis_multi_point (g MULTIPOINT); SHOW FIELDS FROM gis_multi_point; INSERT INTO gis_multi_point VALUES (MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20 20)')), (MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')), (MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4, 10))))); URL: https://mariadb.com/kb/en/mpointfromtext/https://mariadb.com/kb/en/mpointfromtext/ 3(MPolyFromTextSyntax ------ MPolyFromText(wkt[,srid]) MultiPolygonFromText(wkt[,srid]) Description ----------- Constructs a MULTIPOLYGON value using its WKT representation and SRID. MPolyFromText() and MultiPolygonFromText() are synonyms. Examples -------- CREATE TABLE gis_multi_polygon (g MULTIPOLYGON); SHOW FIELDS FROM gis_multi_polygon; INSERT INTO gis_multi_polygon VALUES (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')), (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')), (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3))))))); URL: https://mariadb.com/kb/en/mpolyfromtext/https://mariadb.com/kb/en/mpolyfromtext/f2MultiLineStringFromTextA synonym for MLineFromText. URL: https://mariadb.com/kb/en/multilinestringfromtext/https://mariadb.com/kb/en/multilinestringfromtext/b-MultiPointFromTextA synonym for MPointFromText. URL: https://mariadb.com/kb/en/multipointfromtext/https://mariadb.com/kb/en/multipointfromtext/c/MultiPolygonFromTextA synonym for MPolyFromText. URL: https://mariadb.com/kb/en/multipolygonfromtext/https://mariadb.com/kb/en/multipolygonfromtext/ c,PointFromTextA synonym for ST_PointFromText. URL: https://mariadb.com/kb/en/wkt-pointfromtext/https://mariadb.com/kb/en/wkt-pointfromtext/ a+PolyFromTextA synonym for ST_PolyFromText. URL: https://mariadb.com/kb/en/wkt-polyfromtext/https://mariadb.com/kb/en/wkt-polyfromtext/`*PolygonFromTextA synonym for ST_PolyFromText. URL: https://mariadb.com/kb/en/polygonfromtext/https://mariadb.com/kb/en/polygonfromtext/ C$ST_AsTextSyntax ------ ST_AsText(g) AsText(g) ST_AsWKT(g) AsWKT(g) Description ----------- Converts a value in internal geometry format to its WKT representation and returns the string result. ST_AsText(), AsText(), ST_AsWKT() and AsWKT() are all synonyms. Examples -------- SET @g = 'LineString(1 1,4 4,6 6)'; SELECT ST_AsText(ST_GeomFromText(@g)); +--------------------------------+ | ST_AsText(ST_GeomFromText(@g)) | +--------------------------------+ | LINESTRING(1 1,4 4,6 6) | +--------------------------------+ URL: https://mariadb.com/kb/en/st_astext/https://mariadb.com/kb/en/st_astext/U#ST_ASWKTA synonym for ST_ASTEXT(). URL: https://mariadb.com/kb/en/st_aswkt/https://mariadb.com/kb/en/st_aswkt/ o.ST_GeomCollFromTextSyntax ------ ST_GeomCollFromText(wkt[,srid]) ST_GeometryCollectionFromText(wkt[,srid]) GeomCollFromText(wkt[,srid]) GeometryCollectionFromText(wkt[,srid]) Description ----------- Constructs a GEOMETRYCOLLECTION value using its WKT representation and SRID. ST_GeomCollFromText(), ST_GeometryCollectionFromText(), GeomCollFromText() and GeometryCollectionFromText() are all synonyms. Example CREATE TABLE gis_geometrycollection (g GEOMETRYCOLLECTION); SHOW FIELDS FROM gis_geometrycollection; INSERT INTO gis_geometrycollection VALUES (GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0,10 10))')), (GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6), LineString(Point(3, 6), Point(7, 9)))))), (GeomFromText('GeometryCollection()')), (GeomFromText('GeometryCollection EMPTY')); URL: https://mariadb.com/kb/en/st_geomcollfromtext/https://mariadb.com/kb/en/st_geomcollfromtext/!r8ST_GeometryCollectionFromTextA synonym for ST_GeomCollFromText. URL: https://mariadb.com/kb/en/st_geometrycollectionfromtext/https://mariadb.com/kb/en/st_geometrycollectionfromtext/"d.ST_GeometryFromTextA synonym for ST_GeomFromText. URL: https://mariadb.com/kb/en/st_geometryfromtext/https://mariadb.com/kb/en/st_geometryfromtext/#*ST_GeomFromTextSyntax ------ ST_GeomFromText(wkt[,srid]) ST_GeometryFromText(wkt[,srid]) GeomFromText(wkt[,srid]) GeometryFromText(wkt[,srid]) Description ----------- Constructs a geometry value of any type using its WKT representation and SRID. GeomFromText(), GeometryFromText(), ST_GeomFromText() and ST_GeometryFromText() are all synonyms. Example SET @g = ST_GEOMFROMTEXT('POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1))'); URL: https://mariadb.com/kb/en/st_geomfromtext/https://mariadb.com/kb/en/st_geomfromtext/$*ST_LineFromTextSyntax ------ ST_LineFromText(wkt[,srid]) ST_LineStringFromText(wkt[,srid]) LineFromText(wkt[,srid]) LineStringFromText(wkt[,srid]) Description ----------- Constructs a LINESTRING value using its WKT representation and SRID. ST_LineFromText(), ST_LineStringFromText(), ST_LineFromText() and ST_LineStringFromText() are all synonyms. Examples -------- CREATE TABLE gis_line (g LINESTRING); SHOW FIELDS FROM gis_line; INSERT INTO gis_line VALUES (LineFromText('LINESTRING(0 0,0 10,10 0)')), (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')), (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10))))); URL: https://mariadb.com/kb/en/st_linefromtext/https://mariadb.com/kb/en/st_linefromtext/%f0ST_LineStringFromTextA synonym for ST_LineFromText. URL: https://mariadb.com/kb/en/st_linestringfromtext/https://mariadb.com/kb/en/st_linestringfromtext/&)+ST_PointFromTextSyntax ------ ST_PointFromText(wkt[,srid]) PointFromText(wkt[,srid]) Description ----------- Constructs a POINT value using its WKT representation and SRID. ST_PointFromText() and PointFromText() are synonyms. Examples -------- CREATE TABLE gis_point (g POINT); SHOW FIELDS FROM gis_point; INSERT INTO gis_point VALUES (PointFromText('POINT(10 10)')), (PointFromText('POINT(20 10)')), (PointFromText('POINT(20 20)')), (PointFromWKB(AsWKB(PointFromText('POINT(10 20)')))); URL: https://mariadb.com/kb/en/st_pointfromtext/https://mariadb.com/kb/en/st_pointfromtext/'t*ST_PolyFromTextSyntax ------ ST_PolyFromText(wkt[,srid]) ST_PolygonFromText(wkt[,srid]) PolyFromText(wkt[,srid]) PolygonFromText(wkt[,srid]) Description ----------- Constructs a POLYGON value using its WKT representation and SRID. ST_PolyFromText(), ST_PolygonFromText(), PolyFromText() and ST_PolygonFromText() are all synonyms. Examples -------- CREATE TABLE gis_polygon (g POLYGON); INSERT INTO gis_polygon VALUES (PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')), (PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))')); URL: https://mariadb.com/kb/en/st_polyfromtext/https://mariadb.com/kb/en/st_polyfromtext/xr'J  > ~ G'v Ê (c-ST_PolygonFromTextA synonym for ST_PolyFromText. URL: https://mariadb.com/kb/en/st_polygonfromtext/https://mariadb.com/kb/en/st_polygonfromtext/),Addition Operator (+)Syntax ------ + Description ----------- Addition. If both operands are integers, the result is calculated with BIGINT precision. If either integer is unsigned, the result is also an unsigned integer. For real or string operands, the operand with the highest precision determines the result precision. Examples -------- SELECT 3+5; +-----+ | 3+5 | +-----+ | 8 | +-----+ URL: https://mariadb.com/kb/en/addition-operator/https://mariadb.com/kb/en/addition-operator/*d0Subtraction Operator (-)Syntax ------ - Description ----------- Subtraction. The operator is also used as the unary minus for changing sign. If both operands are integers, the result is calculated with BIGINT precision. If either integer is unsigned, the result is also an unsigned integer, unless the NO_UNSIGNED_SUBTRACTION SQL_MODE is enabled, in which case the result is always signed. For real or string operands, the operand with the highest precision determines the result precision. Examples -------- SELECT 96-9; +------+ | 96-9 | +------+ | 87 | +------+ SELECT 15-17; +-------+ | 15-17 | +-------+ | -2 | +-------+ SELECT 3.66 + 1.333; +--------------+ | 3.66 + 1.333 | +--------------+ | 4.993 | +--------------+ Unary minus: SELECT - (3+5); +---------+ | - (3+5) | +---------+ | -8 | +---------+ URL: https://mariadb.com/kb/en/subtraction-operator-/https://mariadb.com/kb/en/subtraction-operator-/+,Division Operator (/)Syntax ------ / Description ----------- Division operator. Dividing by zero will return NULL. By default, returns four digits after the decimal. This is determined by the server system variable div_precision_increment which by default is four. It can be set from 0 to 30. Dividing by zero returns NULL. If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used (the default since MariaDB 10.2.4), a division by zero also produces a warning. Examples -------- SELECT 4/5; +--------+ | 4/5 | +--------+ | 0.8000 | +--------+ SELECT 300/(2-2); +-----------+ | 300/(2-2) | +-----------+ | NULL | +-----------+ SELECT 300/7; +---------+ | 300/7 | +---------+ | 42.8571 | +---------+ Changing div_precision_increment for the session from the default of four to six: SET div_precision_increment = 6; SELECT 300/7; +-----------+ | 300/7 | +-----------+ | 42.857143 | +-----------+ SELECT 300/7; +-----------+ | 300/7 | +-----------+ | 42.857143 | +-----------+ URL: https://mariadb.com/kb/en/division-operator/https://mariadb.com/kb/en/division-operator/,E2Multiplication Operator (*)Syntax ------ * Description ----------- Multiplication operator. Examples -------- SELECT 7*6; +-----+ | 7*6 | +-----+ | 42 | +-----+ SELECT 1234567890*9876543210; +-----------------------+ | 1234567890*9876543210 | +-----------------------+ | -6253480962446024716 | +-----------------------+ SELECT 18014398509481984*18014398509481984.0; +---------------------------------------+ | 18014398509481984*18014398509481984.0 | +---------------------------------------+ | 324518553658426726783156020576256.0 | +---------------------------------------+ SELECT 18014398509481984*18014398509481984; +-------------------------------------+ | 18014398509481984*18014398509481984 | +-------------------------------------+ | 0 | +-------------------------------------+ URL: https://mariadb.com/kb/en/multiplication-operator/https://mariadb.com/kb/en/multiplication-operator/-!*Modulo Operator (%)Syntax ------ N % M Description ----------- Modulo operator. Returns the remainder of N divided by M. See also MOD. Examples -------- SELECT 1042 % 50; +-----------+ | 1042 % 50 | +-----------+ | 42 | +-----------+ URL: https://mariadb.com/kb/en/modulo-operator/https://mariadb.com/kb/en/modulo-operator/.tDIVSyntax ------ DIV Description ----------- Integer division. Similar to FLOOR(), but is safe with BIGINT values. Incorrect results may occur for non-integer operands that exceed BIGINT range. If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, a division by zero produces an error. Otherwise, it returns NULL. The remainder of a division can be obtained using the MOD operator. Examples -------- SELECT 300 DIV 7; +-----------+ | 300 DIV 7 | +-----------+ | 42 | +-----------+ SELECT 300 DIV 0; +-----------+ | 300 DIV 0 | +-----------+ | NULL | +-----------+ URL: https://mariadb.com/kb/en/div/https://mariadb.com/kb/en/div//ABSSyntax ------ ABS(X) Description ----------- Returns the absolute (non-negative) value of X. If X is not a number, it is converted to a numeric type. Examples -------- SELECT ABS(42); +---------+ | ABS(42) | +---------+ | 42 | +---------+ SELECT ABS(-42); +----------+ | ABS(-42) | +----------+ | 42 | +----------+ SELECT ABS(DATE '1994-01-01'); +------------------------+ | ABS(DATE '1994-01-01') | +------------------------+ | 19940101 | +------------------------+ URL: https://mariadb.com/kb/en/abs/https://mariadb.com/kb/en/abs/0ACOSSyntax ------ ACOS(X) Description ----------- Returns the arc cosine of X, that is, the value whose cosine is X. Returns NULL if X is not in the range -1 to 1. Examples -------- SELECT ACOS(1); +---------+ | ACOS(1) | +---------+ | 0 | +---------+ SELECT ACOS(1.0001); +--------------+ | ACOS(1.0001) | +--------------+ | NULL | +--------------+ SELECT ACOS(0); +-----------------+ | ACOS(0) | +-----------------+ | 1.5707963267949 | +-----------------+ SELECT ACOS(0.234); +------------------+ | ACOS(0.234) | +------------------+ | 1.33460644244679 | +------------------+ URL: https://mariadb.com/kb/en/acos/https://mariadb.com/kb/en/acos/1ASINSyntax ------ ASIN(X) Description ----------- Returns the arc sine of X, that is, the value whose sine is X. Returns NULL if X is not in the range -1 to 1. Examples -------- SELECT ASIN(0.2); +--------------------+ | ASIN(0.2) | +--------------------+ | 0.2013579207903308 | +--------------------+ SELECT ASIN('foo'); +-------------+ | ASIN('foo') | +-------------+ | 0 | +-------------+ SHOW WARNINGS; +---------+------+-----------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------+ | Warning | 1292 | Truncated incorrect DOUBLE value: 'foo' | +---------+------+-----------------------------------------+ URL: https://mariadb.com/kb/en/asin/https://mariadb.com/kb/en/asin/2ATANSyntax ------ ATAN(X) Description ----------- Returns the arc tangent of X, that is, the value whose tangent is X. Examples -------- SELECT ATAN(2); +--------------------+ | ATAN(2) | +--------------------+ | 1.1071487177940904 | +--------------------+ SELECT ATAN(-2); +---------------------+ | ATAN(-2) | +---------------------+ | -1.1071487177940904 | +---------------------+ URL: https://mariadb.com/kb/en/atan/https://mariadb.com/kb/en/atan/3[ ATAN2Syntax ------ ATAN(Y,X), ATAN2(Y,X) Description ----------- Returns the arc tangent of the two variables X and Y. It is similar to calculating the arc tangent of Y / X, except that the signs of both arguments are used to determine the quadrant of the result. Examples -------- SELECT ATAN(-2,2); +---------------------+ | ATAN(-2,2) | +---------------------+ | -0.7853981633974483 | +---------------------+ SELECT ATAN2(PI(),0); +--------------------+ | ATAN2(PI(),0) | +--------------------+ | 1.5707963267948966 | +--------------------+ URL: https://mariadb.com/kb/en/atan2/https://mariadb.com/kb/en/atan2/`u_y4jl xR wm4CEILSyntax ------ CEIL(X) Description ----------- CEIL() is a synonym for CEILING(). URL: https://mariadb.com/kb/en/ceil/https://mariadb.com/kb/en/ceil/5"CEILINGSyntax ------ CEILING(X) Description ----------- Returns the smallest integer value not less than X. Examples -------- SELECT CEILING(1.23); +---------------+ | CEILING(1.23) | +---------------+ | 2 | +---------------+ SELECT CEILING(-1.23); +----------------+ | CEILING(-1.23) | +----------------+ | -1 | +----------------+ URL: https://mariadb.com/kb/en/ceiling/https://mariadb.com/kb/en/ceiling/6LCONVSyntax ------ CONV(N,from_base,to_base) Description ----------- Converts numbers between different number bases. Returns a string representation of the number N, converted from base from_base to base to_base. Returns NULL if any argument is NULL, or if the second or third argument are not in the allowed range. The argument N is interpreted as an integer, but may be specified as an integer or a string. The minimum base is 2 and the maximum base is 36. If to_base is a negative number, N is regarded as a signed number. Otherwise, N is treated as unsigned. CONV() works with 64-bit precision. Some shortcuts for this function are also available: BIN(), OCT(), HEX(), UNHEX(). Also, MariaDB allows binary literal values and hexadecimal literal values. Examples -------- SELECT CONV('a',16,2); +----------------+ | CONV('a',16,2) | +----------------+ | 1010 | +----------------+ SELECT CONV('6E',18,8); +-----------------+ | CONV('6E',18,8) | +-----------------+ | 172 | +-----------------+ SELECT CONV(-17,10,-18); +------------------+ | CONV(-17,10,-18) | +------------------+ | -H | +------------------+ SELECT CONV(12+'10'+'10'+0xa,10,10); +------------------------------+ | CONV(12+'10'+'10'+0xa,10,10) | +------------------------------+ | 42 | +------------------------------+ URL: https://mariadb.com/kb/en/conv/https://mariadb.com/kb/en/conv/7COSSyntax ------ COS(X) Description ----------- Returns the cosine of X, where X is given in radians. Examples -------- SELECT COS(PI()); +-----------+ | COS(PI()) | +-----------+ | -1 | +----------- URL: https://mariadb.com/kb/en/cos/https://mariadb.com/kb/en/cos/8COTSyntax ------ COT(X) Description ----------- Returns the cotangent of X. Examples -------- SELECT COT(42); +--------------------+ | COT(42) | +--------------------+ | 0.4364167060752729 | +--------------------+ SELECT COT(12); +---------------------+ | COT(12) | +---------------------+ | -1.5726734063976893 | +---------------------+ SELECT COT(0); ERROR 1690 (22003): DOUBLE value is out of range in 'cot(0)' URL: https://mariadb.com/kb/en/cot/https://mariadb.com/kb/en/cot/9P CRC32Syntax ------ CRC32(expr) Description ----------- Computes a cyclic redundancy check value and returns a 32-bit unsigned value. The result is NULL if the argument is NULL. The argument is expected to be a string and (if possible) is treated as one if it is not. Examples -------- SELECT CRC32('MariaDB'); +------------------+ | CRC32('MariaDB') | +------------------+ | 4227209140 | +------------------+ SELECT CRC32('mariadb'); +------------------+ | CRC32('mariadb') | +------------------+ | 2594253378 | +------------------+ URL: https://mariadb.com/kb/en/crc32/https://mariadb.com/kb/en/crc32/:G"DEGREESSyntax ------ DEGREES(X) Description ----------- Returns the argument X, converted from radians to degrees. This is the converse of the RADIANS() function. Examples -------- SELECT DEGREES(PI()); +---------------+ | DEGREES(PI()) | +---------------+ | 180 | +---------------+ SELECT DEGREES(PI() / 2); +-------------------+ | DEGREES(PI() / 2) | +-------------------+ | 90 | +-------------------+ SELECT DEGREES(45); +-----------------+ | DEGREES(45) | +-----------------+ | 2578.3100780887 | +-----------------+ URL: https://mariadb.com/kb/en/degrees/https://mariadb.com/kb/en/degrees/;EXPSyntax ------ EXP(X) Description ----------- Returns the value of e (the base of natural logarithms) raised to the power of X. The inverse of this function is LOG() (using a single argument only) or LN(). If X is NULL, this function returns NULL. Examples -------- SELECT EXP(2); +------------------+ | EXP(2) | +------------------+ | 7.38905609893065 | +------------------+ SELECT EXP(-2); +--------------------+ | EXP(-2) | +--------------------+ | 0.1353352832366127 | +--------------------+ SELECT EXP(0); +--------+ | EXP(0) | +--------+ | 1 | +--------+ SELECT EXP(NULL); +-----------+ | EXP(NULL) | +-----------+ | NULL | +-----------+ URL: https://mariadb.com/kb/en/exp/https://mariadb.com/kb/en/exp/<q FLOORSyntax ------ FLOOR(X) Description ----------- Returns the largest integer value not greater than X. Examples -------- SELECT FLOOR(1.23); +-------------+ | FLOOR(1.23) | +-------------+ | 1 | +-------------+ SELECT FLOOR(-1.23); +--------------+ | FLOOR(-1.23) | +--------------+ | -2 | +--------------+ URL: https://mariadb.com/kb/en/floor/https://mariadb.com/kb/en/floor/=LNSyntax ------ LN(X) Description ----------- Returns the natural logarithm of X; that is, the base-e logarithm of X. If X is less than or equal to 0, or NULL, then NULL is returned. The inverse of this function is EXP(). Examples -------- SELECT LN(2); +-------------------+ | LN(2) | +-------------------+ | 0.693147180559945 | +-------------------+ SELECT LN(-2); +--------+ | LN(-2) | +--------+ | NULL | +--------+ URL: https://mariadb.com/kb/en/ln/https://mariadb.com/kb/en/ln/>>LOGSyntax ------ LOG(X), LOG(B,X) Description ----------- If called with one parameter, this function returns the natural logarithm of X. If X is less than or equal to 0, then NULL is returned. If called with two parameters, it returns the logarithm of X to the base B. If B is URL: https://mariadb.com/kb/en/log/https://mariadb.com/kb/en/log/? LOG10Syntax ------ LOG10(X) Description ----------- Returns the base-10 logarithm of X. Examples -------- SELECT LOG10(2); +-------------------+ | LOG10(2) | +-------------------+ | 0.301029995663981 | +-------------------+ SELECT LOG10(100); +------------+ | LOG10(100) | +------------+ | 2 | +------------+ SELECT LOG10(-100); +-------------+ | LOG10(-100) | +-------------+ | NULL | +-------------+ URL: https://mariadb.com/kb/en/log10/https://mariadb.com/kb/en/log10/@LOG2Syntax ------ LOG2(X) Description ----------- Returns the base-2 logarithm of X. Examples -------- SELECT LOG2(4398046511104); +---------------------+ | LOG2(4398046511104) | +---------------------+ | 42 | +---------------------+ SELECT LOG2(65536); +-------------+ | LOG2(65536) | +-------------+ | 16 | +-------------+ SELECT LOG2(-100); +------------+ | LOG2(-100) | +------------+ | NULL | +------------+ URL: https://mariadb.com/kb/en/log2/https://mariadb.com/kb/en/log2/BOCTSyntax ------ OCT(N) Description ----------- Returns a string representation of the octal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,8). Returns NULL if N is NULL. Examples -------- SELECT OCT(34); +---------+ | OCT(34) | +---------+ | 42 | +---------+ SELECT OCT(12); +---------+ | OCT(12) | +---------+ | 14 | +---------+ URL: https://mariadb.com/kb/en/oct/https://mariadb.com/kb/en/oct/`U Sm4> ~= 3 0} 44A9MODSyntax ------ MOD(N,M), N % M, N MOD M Description ----------- Modulo operation. Returns the remainder of N divided by M. See also Modulo Operator. If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, any number modulus zero produces an error. Otherwise, it returns NULL. The integer part of a division can be obtained using DIV. Examples -------- SELECT 1042 % 50; +-----------+ | 1042 % 50 | +-----------+ | 42 | +-----------+ SELECT MOD(234, 10); +--------------+ | MOD(234, 10) | +--------------+ | 4 | +--------------+ SELECT 253 % 7; +---------+ | 253 % 7 | +---------+ | 1 | +---------+ SELECT MOD(29,9); +-----------+ | MOD(29,9) | +-----------+ | 2 | +-----------+ SELECT 29 MOD 9; +----------+ | 29 MOD 9 | +----------+ | 2 | +----------+ URL: https://mariadb.com/kb/en/mod/https://mariadb.com/kb/en/mod/C#PISyntax ------ PI() Description ----------- Returns the value of π (pi). The default number of decimal places displayed is six, but MariaDB uses the full double-precision value internally. Examples -------- SELECT PI(); +----------+ | PI() | +----------+ | 3.141593 | +----------+ SELECT PI()+0.0000000000000000000000; +-------------------------------+ | PI()+0.0000000000000000000000 | +-------------------------------+ | 3.1415926535897931159980 | +-------------------------------+ URL: https://mariadb.com/kb/en/pi/https://mariadb.com/kb/en/pi/DfPOWSyntax ------ POW(X,Y) Description ----------- Returns the value of X raised to the power of Y. POWER() is a synonym. Examples -------- SELECT POW(2,3); +----------+ | POW(2,3) | +----------+ | 8 | +----------+ SELECT POW(2,-2); +-----------+ | POW(2,-2) | +-----------+ | 0.25 | +-----------+ URL: https://mariadb.com/kb/en/pow/https://mariadb.com/kb/en/pow/E POWERSyntax ------ POWER(X,Y) Description ----------- This is a synonym for POW(), which returns the value of X raised to the power of Y. URL: https://mariadb.com/kb/en/power/https://mariadb.com/kb/en/power/F"RADIANSSyntax ------ RADIANS(X) Description ----------- Returns the argument X, converted from degrees to radians. Note that π radians equals 180 degrees. This is the converse of the DEGREES() function. Examples -------- SELECT RADIANS(45); +-------------------+ | RADIANS(45) | +-------------------+ | 0.785398163397448 | +-------------------+ SELECT RADIANS(90); +-----------------+ | RADIANS(90) | +-----------------+ | 1.5707963267949 | +-----------------+ SELECT RADIANS(PI()); +--------------------+ | RADIANS(PI()) | +--------------------+ | 0.0548311355616075 | +--------------------+ SELECT RADIANS(180); +------------------+ | RADIANS(180) | +------------------+ | 3.14159265358979 | +------------------+ URL: https://mariadb.com/kb/en/radians/https://mariadb.com/kb/en/radians/GRANDSyntax ------ RAND(), RAND(N) Description ----------- Returns a random DOUBLE precision floating point value v in the range 0 URL: https://mariadb.com/kb/en/rand/https://mariadb.com/kb/en/rand/H ROUNDSyntax ------ ROUND(X), ROUND(X,D) Description ----------- Rounds the argument X to D decimal places. The rounding algorithm depends on the data type of X. D defaults to 0 if not specified. D can be negative to cause D digits left of the decimal point of the value X to become zero. Examples -------- SELECT ROUND(-1.23); +--------------+ | ROUND(-1.23) | +--------------+ | -1 | +--------------+ SELECT ROUND(-1.58); +--------------+ | ROUND(-1.58) | +--------------+ | -2 | +--------------+ SELECT ROUND(1.58); +-------------+ | ROUND(1.58) | +-------------+ | 2 | +-------------+ SELECT ROUND(1.298, 1); +-----------------+ | ROUND(1.298, 1) | +-----------------+ | 1.3 | +-----------------+ SELECT ROUND(1.298, 0); +-----------------+ | ROUND(1.298, 0) | +-----------------+ | 1 | +-----------------+ SELECT ROUND(23.298, -1); +-------------------+ | ROUND(23.298, -1) | +-------------------+ | 20 | +-------------------+ URL: https://mariadb.com/kb/en/round/https://mariadb.com/kb/en/round/ISIGNSyntax ------ SIGN(X) Description ----------- Returns the sign of the argument as -1, 0, or 1, depending on whether X is negative, zero, or positive. Examples -------- SELECT SIGN(-32); +-----------+ | SIGN(-32) | +-----------+ | -1 | +-----------+ SELECT SIGN(0); +---------+ | SIGN(0) | +---------+ | 0 | +---------+ SELECT SIGN(234); +-----------+ | SIGN(234) | +-----------+ | 1 | +-----------+ URL: https://mariadb.com/kb/en/sign/https://mariadb.com/kb/en/sign/J@SINSyntax ------ SIN(X) Description ----------- Returns the sine of X, where X is given in radians. Examples -------- SELECT SIN(1.5707963267948966); +-------------------------+ | SIN(1.5707963267948966) | +-------------------------+ | 1 | +-------------------------+ SELECT SIN(PI()); +----------------------+ | SIN(PI()) | +----------------------+ | 1.22460635382238e-16 | +----------------------+ SELECT ROUND(SIN(PI())); +------------------+ | ROUND(SIN(PI())) | +------------------+ | 0 | +------------------+ URL: https://mariadb.com/kb/en/sin/https://mariadb.com/kb/en/sin/K&SQRTSyntax ------ SQRT(X) Description ----------- Returns the square root of X. If X is negative, NULL is returned. Examples -------- SELECT SQRT(4); +---------+ | SQRT(4) | +---------+ | 2 | +---------+ SELECT SQRT(20); +------------------+ | SQRT(20) | +------------------+ | 4.47213595499958 | +------------------+ SELECT SQRT(-16); +-----------+ | SQRT(-16) | +-----------+ | NULL | +-----------+ SELECT SQRT(1764); +------------+ | SQRT(1764) | +------------+ | 42 | +------------+ URL: https://mariadb.com/kb/en/sqrt/https://mariadb.com/kb/en/sqrt/LTANSyntax ------ TAN(X) Description ----------- Returns the tangent of X, where X is given in radians. Examples -------- SELECT TAN(0.7853981633974483); +-------------------------+ | TAN(0.7853981633974483) | +-------------------------+ | 0.9999999999999999 | +-------------------------+ SELECT TAN(PI()); +-----------------------+ | TAN(PI()) | +-----------------------+ | -1.22460635382238e-16 | +-----------------------+ SELECT TAN(PI()+1); +-----------------+ | TAN(PI()+1) | +-----------------+ | 1.5574077246549 | +-----------------+ SELECT TAN(RADIANS(PI())); +--------------------+ | TAN(RADIANS(PI())) | +--------------------+ | 0.0548861508080033 | +--------------------+ URL: https://mariadb.com/kb/en/tan/https://mariadb.com/kb/en/tan/@ No6*Plugin OverviewS))MBR DefinitionDescription ----------- The MBR (Minimum Bounding Rectangle), or Envelope is the bounding geometry, formed by the minimum and maximum (X,Y) coordinates: Examples -------- ((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY)) URL: https://mariadb.com/kb/en/mbr-definition/https://mariadb.com/kb/en/mbr-definition/T &MBRContainsSyntax ------ MBRContains(g1,g2) Description ----------- Returns 1 or 0 to indicate whether the Minimum Bounding Rectangle of g1 contains the Minimum Bounding Rectangle of g2. This tests the opposite relationship as MBRWithin(). Examples -------- SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Point(1 1)'); SELECT MBRContains(@g1,@g2), MBRContains(@g2,@g1); +----------------------+----------------------+ | MBRContains(@g1,@g2) | MBRContains(@g2,@g1) | +----------------------+----------------------+ | 1 | 0 | +----------------------+----------------------+ URL: https://mariadb.com/kb/en/mbrcontains/https://mariadb.com/kb/en/mbrcontains/nU3=Wwoj  LEYtP hG <xM#TRUNCATEThis page documents the TRUNCATE function. See TRUNCATE TABLE for the DDL statement. Syntax ------ TRUNCATE(X,D) Description ----------- Returns the number X, truncated to D decimal places. If D is 0, the result has no decimal point or fractional part. D can be negative to cause D digits left of the decimal point of the value X to become zero. Examples -------- SELECT TRUNCATE(1.223,1); +-------------------+ | TRUNCATE(1.223,1) | +-------------------+ | 1.2 | +-------------------+ SELECT TRUNCATE(1.999,1); +-------------------+ | TRUNCATE(1.999,1) | +-------------------+ | 1.9 | +-------------------+ SELECT TRUNCATE(1.999,0); +-------------------+ | TRUNCATE(1.999,0) | +-------------------+ | 1 | +-------------------+ SELECT TRUNCATE(-1.999,1); +--------------------+ | TRUNCATE(-1.999,1) | +--------------------+ | -1.9 | +--------------------+ SELECT TRUNCATE(122,-2); +------------------+ | TRUNCATE(122,-2) | +------------------+ | 100 | +------------------+ SELECT TRUNCATE(10.28*100,0); +-----------------------+ | TRUNCATE(10.28*100,0) | +-----------------------+ | 1028 | +-----------------------+ URL: https://mariadb.com/kb/en/truncate/https://mariadb.com/kb/en/truncate/OE)INSTALL PLUGINSyntax ------ INSTALL PLUGIN [IF NOT EXISTS] plugin_name SONAME 'plugin_library' Description ----------- This statement installs an individual plugin from the specified library. To install the whole library (which could be required), use INSTALL SONAME. plugin_name is the name of the plugin as defined in the plugin declaration structure contained in the library file. Plugin names are not case sensitive. For maximal compatibility, plugin names should be limited to ASCII letters, digits, and underscore, because they are used in C source files, shell command lines, M4 and Bourne shell scripts, and SQL environments. plugin_library is the name of the shared library that contains the plugin code. Before MariaDB 5.5.21, the name should include the file name extension (for example, libmyplugin.so or libmyplugin.dll). Starting from MariaDB 5.5.21, the file name extension can be omitted (which makes the statement look the same on all architectures). The shared library must be located in the plugin directory (that is, the directory named by the plugin_dir system variable). The library must be in the plugin directory itself, not in a subdirectory. By default, plugin_dir is plugin directory under the directory named by the pkglibdir configuration variable, but it can be changed by setting the value of plugin_dir at server startup. For example, set its value in a my.cnf file: [mysqld] plugin_dir=/path/to/plugin/directory If the value of plugin_dir is a relative path name, it is taken to be relative to the MySQL base directory (the value of the basedir system variable). INSTALL PLUGIN adds a line to the mysql.plugin table that describes the plugin. This table contains the plugin name and library file name. INSTALL PLUGIN causes the server to read option (my.cnf) files just as during server startup. This enables the plugin to pick up any relevant options from those files. It is possible to add plugin options to an option file even before loading a plugin (if the loose prefix is used). It is also possible to uninstall a plugin, edit my.cnf, and install the plugin again. Restarting the plugin this way enables it to the new option values without a server restart. Before MySQL 5.1.33, a plugin was started with each option set to its default value. INSTALL PLUGIN also loads and initializes the plugin code to make the plugin available for use. A plugin is initialized by executing its initialization function, which handles any setup that the plugin must perform before it can be used. To use INSTALL PLUGIN, you must have the INSERT privilege for the mysql.plugin table. At server startup, the server loads and initializes any plugin that is listed in the mysql.plugin table. This means that a plugin is installed with INSTALL PLUGIN only once, not every time the server starts. Plugin loading at startup does not occur if the server is started with the --skip-grant-tables option. When the server shuts down, it executes the deinitialization function for each plugin that is loaded so that the plugin has a chance to perform any final cleanup. If you need to load plugins for a single server startup when the --skip-grant-tables option is given (which tells the server not to read system tables), use the --plugin-load mysqld option. IF NOT EXISTS When the IF NOT EXISTS clause is used, MariaDB will return a note instead of an error if the specified plugin already exists. See SHOW WARNINGS. Examples -------- INSTALL PLUGIN sphinx SONAME 'ha_sphinx.so'; Starting from MariaDB 5.5.21, the extension can be omitted: INSTALL PLUGIN innodb SONAME 'ha_xtradb'; From MariaDB 10.4.0: INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example'; Query OK, 0 rows affected (0.104 sec) INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example'; Query OK, 0 rows affected, 1 warning (0.000 sec) SHOW WARNINGS; +-------+------+------------------------------------+ | Level | Code | Message | +-------+------+------------------------------------+ | Note | 1968 | Plugin 'example' already installed | +-------+------+------------------------------------+ URL: https://mariadb.com/kb/en/install-plugin/https://mariadb.com/kb/en/install-plugin/V#MBREqualSyntax ------ MBREqual(g1,g2) Description ----------- Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 are the same. Examples -------- SET @g1=GEOMFROMTEXT('LINESTRING(0 0, 1 2)'); SET @g2=GEOMFROMTEXT('POLYGON((0 0, 0 2, 1 2, 1 0, 0 0))'); SELECT MbrEqual(@g1,@g2); +-------------------+ | MbrEqual(@g1,@g2) | +-------------------+ | 1 | +-------------------+ SET @g1=GEOMFROMTEXT('LINESTRING(0 0, 1 3)'); SET @g2=GEOMFROMTEXT('POLYGON((0 0, 0 2, 1 4, 1 0, 0 0))'); SELECT MbrEqual(@g1,@g2); +-------------------+ | MbrEqual(@g1,@g2) | +-------------------+ | 0 | +-------------------+ URL: https://mariadb.com/kb/en/mbrequal/https://mariadb.com/kb/en/mbrequal/Z $MBRWithinSyntax ------ MBRWithin(g1,g2) Description ----------- Returns 1 or 0 to indicate whether the Minimum Bounding Rectangle of g1 is within the Minimum Bounding Rectangle of g2. This tests the opposite relationship as MBRContains(). Examples -------- SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((0 0,0 5,5 5,5 0,0 0))'); SELECT MBRWithin(@g1,@g2), MBRWithin(@g2,@g1); +--------------------+--------------------+ | MBRWithin(@g1,@g2) | MBRWithin(@g2,@g1) | +--------------------+--------------------+ | 1 | 0 | +--------------------+--------------------+ URL: https://mariadb.com/kb/en/mbrwithin/https://mariadb.com/kb/en/mbrwithin/\ &IF FunctionSyntax ------ IF(expr1,expr2,expr3) Description ----------- If expr1 is TRUE (expr1 0 and expr1 NULL) then IF() returns expr2; otherwise it returns expr3. IF() returns a numeric or string value, depending on the context in which it is used. Note: There is also an IF statement which differs from the IF() function described here. Examples -------- SELECT IF(1>2,2,3); +-------------+ | IF(1>2,2,3) | +-------------+ | 3 | +-------------+ SELECT IF(1 URL: https://mariadb.com/kb/en/if-function/https://mariadb.com/kb/en/if-function/6:dk 'Plugins are server components that enhance MariaDB in some way. These can be anything from new storage engines, plugins for enhancing full-text parsing, or even small enhancements, such as a plugin to get a timestamp as an integer. Querying Plugin Information There are a number of ways to see which plugins are currently active. A server almost always has a large number of active plugins, because the server contains a large number of built-in plugins, which are active by default and cannot be uninstalled. Querying Plugin Information with SHOW PLUGINS The SHOW PLUGINS statement can be used to query information about all active plugins. For example: SHOW PLUGINS; +----------------------------+----------+--------------------+---------+---------+ | Name | Status | Type | Library | License | +----------------------------+----------+--------------------+---------+---------+ ... | mysql_native_password | ACTIVE | AUTHENTICATION | NULL | GPL | | mysql_old_password | ACTIVE | AUTHENTICATION | NULL | GPL | | MRG_MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | ... +----------------------------+----------+--------------------+---------+---------+ If a plugin's Library column has the NULL value, then the plugin is built-in, and it cannot be uninstalled. Querying Plugin Information with information_schema.PLUGINS The information_schema.PLUGINS table can be queried to get more detailed information about plugins. For example: SELECT * FROM information_schema.PLUGINS\G ... *************************** 6. row *************************** PLUGIN_NAME: CSV PLUGIN_VERSION: 1.0 PLUGIN_STATUS: ACTIVE PLUGIN_TYPE: STORAGE ENGINE PLUGIN_TYPE_VERSION: 100003.0 PLUGIN_LIBRARY: NULL PLUGIN_LIBRARY_VERSION: NULL PLUGIN_AUTHOR: Brian Aker, MySQL AB PLUGIN_DESCRIPTION: CSV storage engine PLUGIN_LICENSE: GPL LOAD_OPTION: FORCE PLUGIN_MATURITY: Stable PLUGIN_AUTH_VERSION: 1.0 *************************** 7. row *************************** PLUGIN_NAME: MEMORY PLUGIN_VERSION: 1.0 PLUGIN_STATUS: ACTIVE PLUGIN_TYPE: STORAGE ENGINE PLUGIN_TYPE_VERSION: 100003.0 PLUGIN_LIBRARY: NULL PLUGIN_LIBRARY_VERSION: NULL PLUGIN_AUTHOR: MySQL AB PLUGIN_DESCRIPTION: Hash based, stored in memory, useful for temporary tables PLUGIN_LICENSE: GPL LOAD_OPTION: FORCE PLUGIN_MATURITY: Stable PLUGIN_AUTH_VERSION: 1.0 ... If a plugin's PLUGIN_LIBRARY column has the NULL value, then the plugin is built-in, and it cannot be uninstalled. Querying Plugin Information with mysql.plugin The mysql.plugin table can be queried to get information about installed plugins. This table only contains information about plugins that have been installed via the following methods: The INSTALL SONAME statement. The INSTALL PLUGIN statement. The mysql_plugin utility. This table does not contain information about: Built-in plugins. Plugins loaded with the --plugin-load-add option. Plugins loaded with the --plugin-load option. This table only contains enough information to reload the plugin when the server is restarted, which means it only contains the plugin name and the plugin library. For example: SELECT * FROM mysql.plugin; +------+------------+ | name | dl | +------+------------+ | PBXT | libpbxt.so | +------+------------+ Installing a Plugin There are three primary ways to install a plugin: A plugin can be installed dynamically with an SQL statement. A plugin can be installed with a mysqld option, but it requires a server restart. A plugin can be installed with the mysql_plugin utility, while the server is completely offline. When you are installing a plugin, you also have to ensure that: The server's plugin directory is properly configured, and the plugin's library is in the plugin directory. The server's minimum plugin maturity is properly configured, and the plugin is mature enough to be installed. Installing a Plugin Dynamically A plugin can be installed dynamically by executing either the INSTALL SONAME or the INSTALL PLUGIN statement. If a plugin is installed with one of these statements, then a record will be added to the mysql.plugins table for the plugin. This means that the plugin will automatically be loaded every time the server restarts, unless specifically uninstalled or deactivated. Installing a Plugin with INSTALL SONAME You can install a plugin dynamically by executing the INSTALL SONAME statement. INSTALL SONAME installs all plugins from the given plugin library. This could be required for some plugin libraries. For example, to install all plugins in the server_audit plugin library (which is currently only the server_audit audit plugin), you could execute the following: INSTALL SONAME 'server_audit'; Installing a Plugin with INSTALL PLUGIN You can install a plugin dynamically by executing the INSTALL PLUGIN statement. INSTALL PLUGIN installs a single plugin from the given plugin library. For example, to install the server_audit audit plugin from the server_audit plugin library, you could execute the following: INSTALL PLUGIN server_audit SONAME 'server_audit'; Installing a Plugin with Plugin Load Options A plugin can be installed with a mysqld option by providing either the --plugin-load-add or the --plugin-load option. If a plugin is installed with one of these options, then a record will not be added to the mysql.plugins table for the plugin. This means that if the server is restarted without the same option set, then the plugin will not automatically be loaded. Installing a Plugin with --plugin-load-add You can install a plugin with the --plugin-load-add option by specifying the option as a command-line argument to mysqld or by specifying the option in a relevant server option group in an option file. The --plugin-load-add option uses the following format: Plugins can be specified in the format name=library, where name is the plugin name and library is the plugin library. This format installs a single plugin from the given plugin library. Plugins can also be specified in the format library, where library is the plugin library. This format installs all plugins from the given plugin library. Multiple plugins can be specified by separating them with semicolons. For example, to install all plugins in the server_audit plugin library (which is currently only the server_audit audit plugin) and also the ed25519 authentication plugin from the auth_ed25519 plugin library, you could set the option to the following values on the command-line: $ mysqld --user=mysql --plugin-load-add='server_audit' --plugin-load-add='ed25519=auth_ed25519' You could also set the option to the same values in an option file: [mariadb] ... plugin_load_add = server_audit plugin_load_add = ed25519=auth_ed25519 Special care must be taken when specifying both the --plugin-load option and the --plugin-load-add option together. The --plugin-load option resets the plugin load list, and this can cause unexpected problems if you are not aware. The --plugin-load-add option does not reset the plugin load list, so it is much safer to use. See Specifying Multiple Plugin Load Options for more information. Installing a Plugin with --plugin-load You can install a plugin with the --plugin-load option by specifying the option as a command-line argument to mysqld or by specifying the option in a relevant server option group in an option file. The --plugin-load option uses the following format: Plugins can be specified in the format name=library, where name is the plugin name and library is the plugin library. This format installs a single plugin from the given plugin library. Plugins can also be specified in the format library, where library is the plugin library. This format installs all plugins from the given plugin library. Multiple plugins can be specified by separating them with semicolons. For example, to install all plugins in the server_audit plugin library (which is currently only the server_audit audit plugin) and also the ed25519 authentication plugin from the auth_ed25519 plugin library, you could set the option to the following values on the command-line: $ mysqld --user=mysql --plugin-load='server_Vaudit;ed25519=auth_ed25519' You could also set the option to the same values in an option file: [mariadb] ... plugin_load = server_audit;ed25519=auth_ed25519 Special care must be taken when specifying the --plugin-load option multiple times, or when specifying both the --plugin-load option and the --plugin-load-add option together. The --plugin-load option resets the plugin load list, and this can cause unexpected problems if you are not aware. The --plugin-load-add option does not reset the plugin load list, so it is much safer to use. See Specifying Multiple Plugin Load Options for more information. Specifying Multiple Plugin Load Options Special care must be taken when specifying the --plugin-load option multiple times, or when specifying both the --plugin-load option and the --plugin-load-add option. The --plugin-load option resets the plugin load list, and this can cause unexpected problems if you are not aware. The --plugin-load-add option does not reset the plugin load list, so it is much safer to use. This can have the following consequences: If the --plugin-load option is specified multiple times, then only the last instance will have any effect. For example, in the following case, the first instance of the option is reset: [mariadb] ... plugin_load = server_audit plugin_load = ed25519=auth_ed25519 If the --plugin-load option is specified after the --plugin-load-add option, then it will also reset the changes made by that option. For example, in the following case, the --plugin-load-add option does not do anything, because the subsequent --plugin-load option resets the plugin load list: [mariadb] ... plugin_load_add = server_audit plugin_load = ed25519=auth_ed25519 In contrast, if the --plugin-load option is specified before the --plugin-load-add option, then it will work fine, because the --plugin-load-add option does not reset the plugin load list. For example, in the following case, both plugins are properly loaded: [mariadb] ... plugin_load = server_audit plugin_load_add = ed25519=auth_ed25519 Installing a Plugin with mysql_plugin A plugin can be installed with the mysql_plugin utility if the server is completely offline. The syntax is: mysql_plugin [options] ENABLE|DISABLE For example, to install the server_audit audit plugin, you could execute the following: mysql_plugin server_audit ENABLE If a plugin is installed with this utility, then a record will be added to the mysql.plugins table for the plugin. This means that the plugin will automatically be loaded every time the server restarts, unless specifically uninstalled or deactivated. Configuring the Plugin Directory When a plugin is being installed, the server looks for the plugin's library in the server's plugin directory. This directory is configured by the plugin_dir system variable. This can be specified as a command-line argument to mysqld or it can be specified in a relevant server option group in an option file. For example: [mariadb] ... plugin_dir = /usr/lib64/mysql/plugin Configuring the Minimum Plugin Maturity When a plugin is being installed, the server compares the plugin's maturity level against the server's minimum allowed plugin maturity. This can help prevent users from using unstable plugins on production servers. This minimum plugin maturity is configured by the plugin_maturity system variable. This can be specified as a command-line argument to mysqld or it can be specified in a relevant server option group in an option file. For example: [mariadb] ... plugin_maturity = stable Configuring Plugin Activation at Server Startup A plugin will be loaded by default when the server starts if: The plugin was installed with the INSTALL SONAME statement. The plugin was installed with the INSTALL PLUGIN statement. The plugin was installed with the mysql_plugin utility. The server is configured to load the plugin with the --plugin-load-add option. The server is configured to load the plugin with the --plugin-load option. This behavior can be changed with special options that take the form --plugin-name. For example, for the server_audit audit plugin, the special option is called --server-audit. The possible values for these special options are: Option Value | Description | OFF | Disables the plugin without removing it from the mysql.plugins table. | ON | Enables the plugin. If the plugin cannot be initialized, then the server will still continue starting up, but the plugin will be disabled. | FORCE | Enables the plugin. If the plugin cannot be initialized, then the server will fail to start with an error. | FORCE_PLUS_PERMANENT | Enables the plugin. If the plugin cannot be initialized, then the server will fail to start with an error. In addition, the plugin cannot be uninstalled with UNINSTALL SONAME or UNINSTALL PLUGIN while the server is running. | A plugin's status can be found by looking at the PLUGIN_STATUS column of the information_schema.PLUGINS table. Uninstalling Plugins Plugins that are found in the mysql.plugin table, that is those that were installed with INSTALL SONAME, INSTALL PLUGIN or mysql_plugin can be uninstalled in one of two ways: The UNINSTALL SONAME or the UNINSTALL PLUGIN statement while the server is running With mysql_plugin while the server is offline. Plugins that were enabled as a --plugin-load option do not need to be uninstalled. If --plugin-load is omitted the next time the server starts, or the plugin is not listed as one of the --plugin-load entries, the plugin will not be loaded. UNINSTALL PLUGIN uninstalls a single installed plugin, while UNINSTALL SONAME uninstalls all plugins belonging to a given library. URL: https://mariadb.com/kb/en/plugin-overview/https://mariadb.com/kb/en/change-master-to/ltiple XA-capable storage engines by default, even if the only "real" storage engine that supports external XA transactions enabled on these builds by default is InnoDB. Therefore, when using one these builds MariaDB would be forced to use a transaction coordinator log by default, which could have performance implications. See Transaction Coordinator Log Overview: MariaDB Galera Cluster for more information. URL: https://mariadb.com/kb/en/xa-transactions/n method for the user account by executing the following: ALTER USER root@localhost IDENTIFIED VIA mysql_native_password USING PASSWORD("verysecret") URL: https://mariadb.com/kb/en/authentication-from-mariadb-104/https://mariadb.com/kb/en/create-user/l&+ { https://mariadb.com/kb/en/plugin-overview/position updated as it applies events. The relay_log_info_file system variable can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example: [mariadb] ... relay_log_info_file=/mariadb/myserver1-relay-log.info GTID Persistence If the slave is replicating binary log events that contain GTIDs, then the slave's SQL thread will write every GTID that it applies to the mysql.gtid_slave_pos table. This GTID can be inspected and modified through the gtid_slave_pos system variable. If the slave has the log_slave_updates system variable enabled and if the slave has the binary log enabled, then every write by the slave's SQL thread will also go into the slave's binary log. This means that GTIDs of replicated transactions would be reflected in the value of the gtid_binlog_pos system variable. Creating a Slave from a Backup The CHANGE MASTER statement is useful for setting up a slave when you have a backup of the master and you also have the binary log position or GTID position corresponding to the backup. After restoring the backup on the slave, you could execute something like this to use the binary log position: CHANGE MASTER TO MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4; START SLAVE; Or you could execute something like this to use the GTID position: SET GLOBAL gtid_slave_pos='0-1-153'; CHANGE MASTER TO MASTER_USE_GTID=slave_pos; START SLAVE; See Setting up a Replication Slave with Mariabackup for more information on how to do this with Mariabackup. Example The following example changes the master and master's binary log coordinates. This is used when you want to set up the slave to replicate the master: CHANGE MASTER TO MASTER_HOST='master2.mycompany.com', MASTER_USER='replication', MASTER_PASSWORD='bigs3cret', MASTER_PORT=3306, MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4, MASTER_CONNECT_RETRY=10; START SLAVE; URL: https://mariadb.com/kb/en/change-master-to/https://mariadb.com/kb/en/xa-transactions/https://mariadb.com/kb/en/authentication-from-mariadb-104/; ALTER TABLE mysql.procs_priv MODIFY Grantor CHAR(141) COLLATE utf8_bin NOT NULL DEFAULT ''; ALTER TABLE mysql.tables_priv MODIFY Grantor CHAR(141) COLLATE utf8_bin NOT NULL DEFAULT ''; FLUSH PRIVILEGES; Anonymous Accounts Anonymous accounts are accounts where the user name portion of the account name is empty. These accounts act as special catch-all accounts. If a user attempts to log into the system from a host, and an anonymous account exists with a host name portion that matches the user's host, then the user will log in as the anonymous account if there is no more specific account match for the user name that the user entered. For example, here are some anonymous accounts: CREATE USER ''@'localhost'; CREATE USER ''@'192.168.0.3'; Fixing a Legacy Default Anonymous Account On some systems, the mysql.db table has some entries for the ''@'%' anonymous account by default. Unfortunately, there is no matching entry in the mysql.user table, which means that this anonymous account doesn't exactly exist, but it does have privileges--usually on the default test database created by mysql_install_db. These account-less privileges are a legacy that is leftover from a time when MySQL's privilege system was less advanced. This situation means that you will run into errors if you try to create a ''@'%' account. For example: CREATE USER ''@'%'; ERROR 1396 (HY000): Operation CREATE USER failed for ''@'%' The fix is to DELETE the row in the mysql.db table and then execute FLUSH PRIVILEGES: DELETE FROM mysql.db WHERE User='' AND Host='%'; FLUSH PRIVILEGES; And then the account can be created: CREATE USER ''@'%'; Query OK, 0 rows affected (0.01 sec) See MDEV-13486 for more information. Password Expiry Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global setting, for example: CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY; See User Password Expiry for more details. Account Locking Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected). For example: CREATE USER 'marijn'@'localhost' ACCOUNT LOCK; See Account Locking for more details. URL: https://mariadb.com/kb/en/create-user/https://mariadb.com/kb/en/alter-user/https://mariadb.com/kb/en/grant/ To flush some of the global caches that take up memory, you could execute the following command: FLUSH LOCAL HOSTS, QUERY CACHE, TABLE_STATISTICS, INDEX_STATISTICS, USER_STATISTICS; URL: https://mariadb.com/kb/en/flush/https://mariadb.com/kb/en/show-slave-status/ssions_reused | 0 | | Ssl_used_session_cache_entries | 0 | | Ssl_verify_depth | 0 | | Ssl_verify_mode | 0 | | Ssl_version | | | Subquery_cache_hit | 0 | | Subquery_cache_miss | 0 | | Syncs | 2 | | Table_locks_immediate | 21 | | Table_locks_waited | 0 | | Tc_log_max_pages_used | 0 | | Tc_log_page_size | 4096 | | Tc_log_page_waits | 0 | | Threadpool_idle_threads | 0 | | Threadpool_threads | 0 | | Threads_cached | 0 | | Threads_connected | 1 | | Threads_created | 2 | | Threads_running | 1 | | Update_scan | 0 | | Uptime | 223 | | Uptime_since_flush_status | 223 | | wsrep_cluster_conf_id | 18446744073709551615 | | wsrep_cluster_size | 0 | | wsrep_cluster_state_uuid | | | wsrep_cluster_status | Disconnected | | wsrep_connected | OFF | | wsrep_local_bf_aborts | 0 | | wsrep_local_index | 18446744073709551615 | | wsrep_provider_name | | | wsrep_provider_vendor | | | wsrep_provider_version | | | wsrep_ready | OFF | | wsrep_thread_count | 0 | +--------------------------------------------------------------+----------------------------------------+ 516 rows in set (0.00 sec) Example of filtered output: SHOW STATUS LIKE 'Key%'; +------------------------+--------+ | Variable_name | Value | +------------------------+--------+ | Key_blocks_not_flushed | 0 | | Key_blocks_unused | 107163 | | Key_blocks_used | 0 | | Key_blocks_warm | 0 | | Key_read_requests | 0 | | Key_reads | 0 | | Key_write_requests | 0 | | Key_writes | 0 | +------------------------+--------+ 8 rows in set (0.00 sec) URL: https://mariadb.com/kb/en/show-status/-------------------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | employees_example | ALL | NULL | NULL | NULL | NULL | 6 | Using where | +------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+ Here, the type is All, which means no index could be used. Looking at the rows count, a full table scan (all six rows) had to be performed in order to retrieve the record. If it's a requirement to search by phone number, an index will have to be created. SHOW EXPLAIN example: SHOW EXPLAIN FOR 1; +------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+ | 1 | SIMPLE | tbl | index | NULL | a | 5 | NULL | 1000107 | Using index | +------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+ 1 row in set, 1 warning (0.00 sec) Example of ref_or_null optimization SELECT * FROM table_name WHERE key_column=expr OR key_column IS NULL; ref_or_null is something that often happens when you use subqueries with NOT IN as then one has to do an extra check for NULL values if the first value didn't have a matching row. URL: https://mariadb.com/kb/en/explain/lV*,/ %{o A:*6 *IyiPs+UNINSTALL PLUGINSyntax ------ UNINSTALL PLUGIN [IF EXISTS] plugin_name Description ----------- This statement removes a single installed plugin. To uninstall the whole library which contains the plugin, use UNINSTALL SONAME. You cannot uninstall a plugin if any table that uses it is open. plugin_name must be the name of some plugin that is listed in the mysql.plugin table. The server executes the plugin's deinitialization function and removes the row for the plugin from the mysql.plugin table, so that subsequent server restarts will not load and initialize the plugin. UNINSTALL PLUGIN does not remove the plugin's shared library file. To use UNINSTALL PLUGIN, you must have the DELETE privilege for the mysql.plugin table. IF EXISTS If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the plugin does not exist. See SHOW WARNINGS. Examples -------- UNINSTALL PLUGIN example; From MariaDB 10.4.0: UNINSTALL PLUGIN IF EXISTS example; Query OK, 0 rows affected (0.099 sec) UNINSTALL PLUGIN IF EXISTS example; Query OK, 0 rows affected, 1 warning (0.000 sec) SHOW WARNINGS; +-------+------+-------------------------------+ | Level | Code | Message | +-------+------+-------------------------------+ | Note | 1305 | PLUGIN example does not exist | +-------+------+-------------------------------+ URL: https://mariadb.com/kb/en/uninstall-plugin/https://mariadb.com/kb/en/uninstall-plugin/Qc )INSTALL SONAMEINSTALL SONAME has been supported since MariaDB 5.5.21. Syntax ------ INSTALL SONAME 'plugin_library' Description ----------- This statement is a variant of INSTALL PLUGIN. It installs all plugins from a given plugin_library. See INSTALL PLUGIN for details. plugin_library is the name of the shared library that contains the plugin code. The file name extension (for example, libmyplugin.so or libmyplugin.dll) can be omitted (which makes the statement look the same on all architectures). The shared library must be located in the plugin directory (that is, the directory named by the plugin_dir system variable). The library must be in the plugin directory itself, not in a subdirectory. By default, plugin_dir is plugin directory under the directory named by the pkglibdir configuration variable, but it can be changed by setting the value of plugin_dir at server startup. For example, set its value in a my.cnf file: [mysqld] plugin_dir=/path/to/plugin/directory If the value of plugin_dir is a relative path name, it is taken to be relative to the MySQL base directory (the value of the basedir system variable). INSTALL SONAME adds one or more lines to the mysql.plugin table that describes the plugin. This table contains the plugin name and library file name. INSTALL SONAME causes the server to read option (my.cnf) files just as during server startup. This enables the plugin to pick up any relevant options from those files. It is possible to add plugin options to an option file even before loading a plugin (if the loose prefix is used). It is also possible to uninstall a plugin, edit my.cnf, and install the plugin again. Restarting the plugin this way enables it to the new option values without a server restart. INSTALL SONAME also loads and initializes the plugin code to make the plugin available for use. A plugin is initialized by executing its initialization function, which handles any setup that the plugin must perform before it can be used. To use INSTALL SONAME, you must have the INSERT privilege for the mysql.plugin table. At server startup, the server loads and initializes any plugin that is listed in the mysql.plugin table. This means that a plugin is installed with INSTALL SONAME only once, not every time the server starts. Plugin loading at startup does not occur if the server is started with the --skip-grant-tables option. When the server shuts down, it executes the deinitialization function for each plugin that is loaded so that the plugin has a chance to perform any final cleanup. If you need to load plugins for a single server startup when the --skip-grant-tables option is given (which tells the server not to read system tables), use the --plugin-load mysqld option. If you need to install only one plugin from a library, use the INSTALL PLUGIN statement. Examples -------- To load the XtraDB storage engine and all of its information_schema tables with one statement, use INSTALL SONAME 'ha_xtradb'; This statement can be used instead of INSTALL PLUGIN even when the library contains only one plugin: INSTALL SONAME 'ha_sequence'; URL: https://mariadb.com/kb/en/install-soname/https://mariadb.com/kb/en/install-soname/R+UNINSTALL SONAMEUNINSTALL SONAME has been supported since MariaDB 5.5.21. Syntax ------ UNINSTALL SONAME [IF EXISTS] 'plugin_library' Description ----------- This statement is a variant of UNINSTALL PLUGIN statement, that removes all plugins belonging to a specified plugin_library. See UNINSTALL PLUGIN for details. plugin_library is the name of the shared library that contains the plugin code. The file name extension (for example, libmyplugin.so or libmyplugin.dll) can be omitted (which makes the statement look the same on all architectures). To use UNINSTALL SONAME, you must have the DELETE privilege for the mysql.plugin table. IF EXISTS If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the plugin library does not exist. See SHOW WARNINGS. Examples -------- To uninstall the XtraDB plugin and all of its information_schema tables with one statement, use UNINSTALL SONAME 'ha_xtradb'; From MariaDB 10.4.0: UNINSTALL SONAME IF EXISTS 'ha_example'; Query OK, 0 rows affected (0.099 sec) UNINSTALL SONAME IF EXISTS 'ha_example'; Query OK, 0 rows affected, 1 warning (0.000 sec) SHOW WARNINGS; +-------+------+-------------------------------------+ | Level | Code | Message | +-------+------+-------------------------------------+ | Note | 1305 | SONAME ha_example.so does not exist | +-------+------+-------------------------------------+ URL: https://mariadb.com/kb/en/uninstall-soname/https://mariadb.com/kb/en/uninstall-soname/]!IFNULLSyntax ------ IFNULL(expr1,expr2) Description ----------- If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used. Examples -------- SELECT IFNULL(1,0); +-------------+ | IFNULL(1,0) | +-------------+ | 1 | +-------------+ SELECT IFNULL(NULL,10); +-----------------+ | IFNULL(NULL,10) | +-----------------+ | 10 | +-----------------+ SELECT IFNULL(1/0,10); +----------------+ | IFNULL(1/0,10) | +----------------+ | 10.0000 | +----------------+ SELECT IFNULL(1/0,'yes'); +-------------------+ | IFNULL(1/0,'yes') | +-------------------+ | yes | +-------------------+ URL: https://mariadb.com/kb/en/ifnull/https://mariadb.com/kb/en/ifnull/^!NULLIFSyntax ------ NULLIF(expr1,expr2) Description ----------- Returns NULL if expr1 = expr2 is true, otherwise returns expr1. This is the same as CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END. Examples -------- SELECT NULLIF(1,1); +-------------+ | NULLIF(1,1) | +-------------+ | NULL | +-------------+ SELECT NULLIF(1,2); +-------------+ | NULLIF(1,2) | +-------------+ | 1 | +-------------+ URL: https://mariadb.com/kb/en/nullif/https://mariadb.com/kb/en/nullif/pap 5V 0U G&MBRDisjointSyntax ------ MBRDisjoint(g1,g2) Description ----------- Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 are disjoint. Two geometries are disjoint if they do not intersect, that is touch or overlap. Examples -------- SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))'); SELECTmbrdisjoint(@g1,@g2); +----------------------+ | mbrdisjoint(@g1,@g2) | +----------------------+ | 1 | +----------------------+ SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))'); SELECT mbrdisjoint(@g1,@g2); +----------------------+ | mbrdisjoint(@g1,@g2) | +----------------------+ | 0 | +----------------------+ URL: https://mariadb.com/kb/en/mbrdisjoint/https://mariadb.com/kb/en/mbrdisjoint/W (MBRIntersectsSyntax ------ MBRIntersects(g1,g2) Description ----------- Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 intersect. Examples -------- SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))'); SELECT mbrintersects(@g1,@g2); +------------------------+ | mbrintersects(@g1,@g2) | +------------------------+ | 1 | +------------------------+ SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))'); SELECT mbrintersects(@g1,@g2); +------------------------+ | mbrintersects(@g1,@g2) | +------------------------+ | 0 | +------------------------+ URL: https://mariadb.com/kb/en/mbrintersects/https://mariadb.com/kb/en/mbrintersects/X &MBROverlapsSyntax ------ MBROverlaps(g1,g2) Description ----------- Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 overlap. The term spatially overlaps is used if two geometries intersect and their intersection results in a geometry of the same dimension but not equal to either of the given geometries. Examples -------- SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))'); SELECT mbroverlaps(@g1,@g2); +----------------------+ | mbroverlaps(@g1,@g2) | +----------------------+ | 0 | +----------------------+ SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))'); SELECT mbroverlaps(@g1,@g2); +----------------------+ | mbroverlaps(@g1,@g2) | +----------------------+ | 0 | +----------------------+ SET @g1 = GeomFromText('Polygon((0 0,0 4,4 4,4 0,0 0))'); SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))'); SELECT mbroverlaps(@g1,@g2); +----------------------+ | mbroverlaps(@g1,@g2) | +----------------------+ | 1 | +----------------------+ URL: https://mariadb.com/kb/en/mbroverlaps/https://mariadb.com/kb/en/mbroverlaps/Y %MBRTouchesSyntax ------ MBRTouches(g1,g2) Description ----------- Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 touch. Two geometries spatially touch if the interiors of the geometries do not intersect, but the boundary of one of the geometries intersects either the boundary or the interior of the other. Examples -------- SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))'); SELECT mbrtouches(@g1,@g2); +---------------------+ | mbrtouches(@g1,@g2) | +---------------------+ | 0 | +---------------------+ SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))'); SELECT mbrtouches(@g1,@g2); +---------------------+ | mbrtouches(@g1,@g2) | +---------------------+ | 1 | +---------------------+ SET @g1 = GeomFromText('Polygon((0 0,0 4,4 4,4 0,0 0))'); SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))'); SELECT mbrtouches(@g1,@g2); +---------------------+ | mbrtouches(@g1,@g2) | +---------------------+ | 0 | +---------------------+ URL: https://mariadb.com/kb/en/mbrtouches/https://mariadb.com/kb/en/mbrtouches/[ (CASE OPERATORSyntax ------ CASE value WHEN [compare_value] THEN result [WHEN [compare_value] THEN result ...] [ELSE result] END CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...] [ELSE result] END Description ----------- The first version returns the result where value=compare_value. The second version returns the result for the first condition that is true. If there was no matching result value, the result after ELSE is returned, or NULL if there is no ELSE part. There is also a CASE statement, which differs from the CASE operator described here. Examples -------- SELECT CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE 'more' END; +------------------------------------------------------------+ | CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE 'more' END | +------------------------------------------------------------+ | one | +------------------------------------------------------------+ SELECT CASE WHEN 1>0 THEN 'true' ELSE 'false' END; +--------------------------------------------+ | CASE WHEN 1>0 THEN 'true' ELSE 'false' END | +--------------------------------------------+ | true | +--------------------------------------------+ SELECT CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2 END; +-----------------------------------------------------+ | CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2 END | +-----------------------------------------------------+ | NULL | +-----------------------------------------------------+ URL: https://mariadb.com/kb/en/case-operator/https://mariadb.com/kb/en/case-operator/ @ _g+CHANGE MASTER TOj 'RESET MASTERRESET MASTER [TO #] Deletes all binary log files listed in the index file, resets the binary log index file to be empty, and creates a new binary log file with a suffix of .000001. If TO # is given, then the first new binary log file will start from number #. This statement is for use only when the master is started for the first time, and should never be used if any slaves are actively replicating from the binary log. URL: https://mariadb.com/kb/en/reset-master/https://mariadb.com/kb/en/reset-master/q P5UNLOCK TABLESSyntax ------ UNLOCK TABLES Description ----------- UNLOCK TABLES explicitly releases any table locks held by the current session. See LOCK TABLES for more information. In addition to releasing table locks acquired by the LOCK TABLES statement, the UNLOCK TABLES statement also releases the global read lock acquired by the FLUSH TABLES WITH READ LOCK statement. The FLUSH TABLES WITH READ LOCK statement is very useful for performing backups. See FLUSH for more information about FLUSH TABLES WITH READ LOCK. URL: https://mariadb.com/kb/en/transactions-unlock-tables/https://mariadb.com/kb/en/transactions-unlock-tables/@ s!*XA Transactions@ u : Authentication from MariaDB 10.4@ v WI& CREATE USER@ w ,% ALTER USERn.?/D3( 4< P KSyntax ------ CHANGE MASTER ['connection_name'] TO master_def [, master_def] ... master_def: MASTER_BIND = 'interface_name' | MASTER_HOST = 'host_name'[ | MASTER_USER = 'user_name' | MASTER_PASSWORD = 'password' | MASTER_PORT = port_num | MASTER_CONNECT_RETRY = interval | MASTER_HEARTBEAT_PERIOD = interval | MASTER_LOG_FILE = 'master_log_name' | MASTER_LOG_POS = master_log_pos | RELAY_LOG_FILE = 'relay_log_name' | RELAY_LOG_POS = relay_log_pos | MASTER_DELAY = interval | MASTER_SSL = {0|1} | MASTER_SSL_CA = 'ca_file_name' | MASTER_SSL_CAPATH = 'ca_directory_name' | MASTER_SSL_CERT = 'cert_file_name' | MASTER_SSL_CRL = 'crl_file_name' | MASTER_SSL_CRLPATH = 'crl_directory_name' | MASTER_SSL_KEY = 'key_file_name' | MASTER_SSL_CIPHER = 'cipher_list' | MASTER_SSL_VERIFY_SERVER_CERT = {0|1} | MASTER_USE_GTID = {current_pos|slave_pos|no} | IGNORE_SERVER_IDS = (server_id_list) | DO_DOMAIN_IDS = ([N,..]) | IGNORE_DOMAIN_IDS = ([N,..]) Description ----------- The CHANGE MASTER statement sets the options that a replication slave uses to connect to and replicate from a replication master. MariaDB until 10.0.7 In MariaDB 10.0.7 and before, the relay_log_purge system variable was silently set to 0 when CHANGE MASTER was executed. Multi-Source Replication Multi-source replication was added in MariaDB 10.0.1. If you are using multi-source replication, then you need to specify a connection name when you execute CHANGE MASTER. There are two ways to do this: Setting the default_master_connection system variable prior to executing CHANGE MASTER. Setting the connection_name parameter when executing CHANGE MASTER. default_master_connection SET default_master_connection = 'gandalf'; STOP SLAVE; CHANGE MASTER TO MASTER_PASSWORD='new3cret'; START SLAVE; connection_name STOP SLAVE 'gandalf'; CHANGE MASTER 'gandalf' TO MASTER_PASSWORD='new3cret'; START SLAVE 'gandalf'; Options Connection Options MASTER_USER The MASTER_USER option for CHANGE MASTER defines the user account that the replication slave will use to connect to the replication master. This user account will need the REPLICATION SLAVE privilege on the master. For example: STOP SLAVE; CHANGE MASTER TO MASTER_USER='repl', MASTER_PASSWORD='new3cret'; START SLAVE; MASTER_PASSWORD The MASTER_USER option for CHANGE MASTER defines the password that the replication slave will use to connect to the replication master as the user account defined by the MASTER_USER option. For example: STOP SLAVE; CHANGE MASTER TO MASTER_PASSWORD='new3cret'; START SLAVE; MASTER_HOST The MASTER_HOST option for CHANGE MASTER defines the hostname or IP address of the replication master. If you set the value of the MASTER_HOST option to the empty string, then that is not the same as not setting the option's value at all. In MariaDB 5.5 and later, if you set the value of the MASTER_HOST option to the empty string, then the CHANGE MASTER command will fail with an error. In MariaDB 5.3 and before, if you set the value of the MASTER_HOST option to the empty string, then the CHANGE MASTER command would succeed, but the subsequent START SLAVE command would fail. For example: STOP SLAVE; CHANGE MASTER TO MASTER_HOST='dbserver1.example.com', MASTER_USER='repl', MASTER_PASSWORD='new3cret', MASTER_USE_GTID=slave_pos; START SLAVE; If you set the value of the MASTER_HOST option in a CHANGE MASTER command, then the slave assumes that the master is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the slave will consider the old values for the master's binary log file name and position to be invalid for the new master. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement, then these values will effectively be ignored anyway. Replication slaves cannot connect to replication masters using Unix socket files or Windows named pipes. The replication slave must connect to the replication master using TCP/IP. MASTER_PORT The MASTER_PORT option for CHANGE MASTER defines the TCP/IP port of the replication master. For example: STOP SLAVE; CHANGE MASTER TO MASTER_HOST='dbserver1.example.com', MASTER_PORT=3307, MASTER_USER='repl', MASTER_PASSWORD='new3cret', MASTER_USE_GTID=slave_pos; START SLAVE; If you set the value of the MASTER_PORT option in a CHANGE MASTER command, then the slave assumes that the master is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the slave will consider the old values for the master's binary log file name and position to be invalid for the new master. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement, then these values will effectively be ignored anyway. Replication slaves cannot connect to replication masters using Unix socket files or Windows named pipes. The replication slave must connect to the replication master using TCP/IP. MASTER_CONNECT_RETRY The MASTER_CONNECT_RETRY option for CHANGE MASTER defines how many seconds that the slave will wait between connection retries. The default is 60. STOP SLAVE; CHANGE MASTER TO MASTER_CONNECT_RETRY=20; START SLAVE; The number of connection attempts is limited by the master_retry_count option. It can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example: [mariadb] ... master_retry_count=4294967295 MASTER_BIND The MASTER_BIND option for CHANGE MASTER is only supported by MySQL 5.6.2 and later and by MySQL NDB Cluster 7.3.1 and later. This option is not yet supported by MariaDB. See MDEV-19248 for more information. The MASTER_BIND option for CHANGE MASTER can be used on replication slaves that have multiple network interfaces to choose which network interface the slave will use to connect to the master. MASTER_HEARTBEAT_PERIOD The MASTER_HEARTBEAT_PERIOD option for CHANGE MASTER can be used to set the interval in seconds between replication heartbeats. Whenever the master's binary log is updated with an event, the waiting period for the next heartbeat is reset. This option's interval argument has the following characteristics: It is a decimal value with a range of 0 to 4294967 seconds. It has a resolution of hundredths of a second. Its smallest valid non-zero value is 0.001. Its default value is the value of the slave_net_timeout system variable divided by 2. If it's set to 0, then heartbeats are disabled. Heartbeats are sent by the master only if there are no unsent events in the binary log file for a period longer than the interval. If the RESET SLAVE statement is executed, then the heartbeat interval is reset to the default. If the slave_net_timeout system variable is set to a value that is lower than the current heartbeat interval, then a warning will be issued. TLS Options The TLS options are used for providing information about TLS. The options can be set even on slaves that are compiled without TLS support. The TLS options are saved to either the default master.info file or the file that is configured by the master_info_file option, but these TLS options are ignored unless the slave supports TLS. See Replication with Secure Connections for more information. MASTER_SSL The MASTER_SSL option for CHANGE MASTER tells the slave whether to force TLS for the connection. The valid values are 0 or 1. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL=1; START SLAVE; MASTER_SSL_CA The MAST)mER_SSL_CA option for CHANGE MASTER defines a path to a PEM file that should contain one or more X509 certificates for trusted Certificate Authorities (CAs) to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE; See Secure Connections Overview: Certificate Authorities (CAs) for more information. MASTER_SSL_CAPATH The MASTER_SSL_CAPATH option for CHANGE MASTER defines a path to a directory that contains one or more PEM files that should each contain one X509 certificate for a trusted Certificate Authority (CA) to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command. This option implies the MASTER_SSL option. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CAPATH='/etc/my.cnf.d/certificates/ca/', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE; See Secure Connections Overview: Certificate Authorities (CAs) for more information. MASTER_SSL_CERT The MASTER_SSL_CERT option for CHANGE MASTER defines a path to the X509 certificate file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE; MASTER_SSL_CRL The MASTER_SSL_CRL option for CHANGE MASTER defines a path to a PEM file that should contain one or more revoked X509 certificates to use for TLS. This option requires that you use the absolute path, not a relative path. This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1, MASTER_SSL_CRL='/etc/my.cnf.d/certificates/crl.pem'; START SLAVE; See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information. MASTER_SSL_CRLPATH The MASTER_SSL_CRLPATH option for CHANGE MASTER defines a path to a directory that contains one or more PEM files that should each contain one revoked X509 certificate to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this variable needs to be run through the openssl rehash command. This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1, MASTER_SSL_CRLPATH='/etc/my.cnf.d/certificates/crl/'; START SLAVE; See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information. MASTER_SSL_KEY The MASTER_SSL_KEY option for CHANGE MASTER defines a path to a private key file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE; MASTER_SSL_CIPHER The MASTER_SSL_CIPHER option for CHANGE MASTER defines the list of permitted ciphers or cipher suites to use for TLS. Besides cipher names, if MariaDB was compiled with OpenSSL, this option could be set to "SSLv3" or "TLSv1.2" to allow all SSLv3 or all TLSv1.2 ciphers. Note that the TLSv1.3 ciphers cannot be excluded when using OpenSSL, even by using this option. See Using TLSv1.3 for details. This option implies the MASTER_SSL option. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1, MASTER_SSL_CIPHER='TLSv1.2'; START SLAVE; MASTER_SSL_VERIFY_SERVER_CERT The MASTER_SSL_VERIFY_SERVER_CERT option for CHANGE MASTER enables server certificate verification. This option is disabled by default. For example: STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE; See Secure Connections Overview: Server Certificate Verification for more information. Binary Log Options These options are related to the binary log position on the master. MASTER_LOG_FILE The MASTER_LOG_FILE option for CHANGE MASTER can be used along with MASTER_LOG_POS to specify the coordinates at which the slave's I/O thread should begin reading from the master's binary logs the next time the thread starts. For example: STOP SLAVE; CHANGE MASTER TO MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4; START SLAVE; The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified. The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement. MASTER_LOG_POS The MASTER_LOG_POS option for CHANGE MASTER can be used along with MASTER_LOG_FILE to specify the coordinates at which the slave's I/O thread should begin reading from the master's binary logs the next time the thread starts. For example: STOP SLAVE; CHANGE MASTER TO MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4; START SLAVE; The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified. The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement. Relay Log Options These options are related to the relay log position on the slave. RELAY_LOG_FILE The RELAY_LOG_FILE option for CHANGE MASTER can be used along with the RELAY_LOG_POS option to specify the coordinates at which the slave's SQL thread should begin reading from the relay log the next time the thread starts. The CHANGE MASTER statement usually deletes all relay log files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS options are specified, then existing relay log files are kept. When you want to change the relay log position, you only need to stop the slave's SQL thread. The slave's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD option for this scenario. For example: STOP SLAVE SQL_THREAD; CHANGE MASTER TO RELAY_LOG_FILE='slave-relay-bin.006', RELAY_LOG_POS=4025; START SLAVE SQL_THREAD; When the value of this option is changed, theuT: metadata about the slave's SQL thread's position in the relay logs will also be changed in the relay-log.info file or the file that is configured by the relay_log_info_file system variable. The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified. RELAY_LOG_POS The RELAY_LOG_POS option for CHANGE MASTER can be used along with the RELAY_LOG_FILE option to specify the coordinates at which the slave's SQL thread should begin reading from the relay log the next time the thread starts. The CHANGE MASTER statement usually deletes all relay log files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS options are specified, then existing relay log files are kept. When you want to change the relay log position, you only need to stop the slave's SQL thread. The slave's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD option for this scenario. For example: STOP SLAVE SQL_THREAD; CHANGE MASTER TO RELAY_LOG_FILE='slave-relay-bin.006', RELAY_LOG_POS=4025; START SLAVE SQL_THREAD; When the value of this option is changed, the metadata about the slave's SQL thread's position in the relay logs will also be changed in the relay-log.info file or the file that is configured by the relay_log_info_file system variable. The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified. GTID Options MASTER_USE_GTID The MASTER_USE_GTID option for CHANGE MASTER was first added in MariaDB 10.0.2 to enable replication with Global Transaction IDs (GTIDs). The MASTER_USE_GTID option for CHANGE MASTER can be used to configure the slave to use the global transaction ID (GTID) when connecting to a master. The possible values are: current_pos - Replicate in GTID mode and use gtid_current_pos as the position to start downloading transactions from the master. slave_pos - Replicate in GTID mode and use gtid_slave_pos as the position to start downloading transactions from the master. no - Don't replicate in GTID mode. For example: STOP SLAVE; CHANGE MASTER TO MASTER_USE_GTID = current_pos; START SLAVE; Or: STOP SLAVE; SET GLOBAL gtid_slave_pos='0-1-153'; CHANGE MASTER TO MASTER_USE_GTID = slave_pos; START SLAVE; Replication Filter Options IGNORE_SERVER_IDS The IGNORE_SERVER_IDS option for CHANGE MASTER can be used to configure a replication slave to ignore binary log events that originated from certain servers. Filtered binary log events will not get logged to the slave’s relay log, and they will not be applied by the slave. The option's value can be specified by providing a comma-separated list of server_id values. For example: STOP SLAVE; CHANGE MASTER TO IGNORE_SERVER_IDS = (3,5); START SLAVE; If you would like to clear a previously set list, then you can set the value to an empty list. For example: STOP SLAVE; CHANGE MASTER TO IGNORE_SERVER_IDS = (); START SLAVE; DO_DOMAIN_IDS The DO_DOMAIN_IDS option for CHANGE MASTER was first added in MariaDB 10.1.2. The DO_DOMAIN_IDS option for CHANGE MASTER can be used to configure a replication slave to only apply binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the slave’s relay log, and they will not be applied by the slave. The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example: STOP SLAVE; CHANGE MASTER TO DO_DOMAIN_IDS = (1,2); START SLAVE; If you would like to clear a previously set list, then you can set the value to an empty list. For example: STOP SLAVE; CHANGE MASTER TO DO_DOMAIN_IDS = (); START SLAVE; The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the DO_DOMAIN_IDS option, and the IGNORE_DOMAIN_IDS option was previously set, then you need to clear the value of the IGNORE_DOMAIN_IDS option. For example: STOP SLAVE; CHANGE MASTER TO IGNORE_DOMAIN_IDS = (), DO_DOMAIN_IDS = (1,2); START SLAVE; The DO_DOMAIN_IDS option can only be specified if the slave is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no in order to use this option. IGNORE_DOMAIN_IDS The IGNORE_DOMAIN_IDS option for CHANGE MASTER was first added in MariaDB 10.1.2. The IGNORE_DOMAIN_IDS option for CHANGE MASTER can be used to configure a replication slave to ignore binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the slave’s relay log, and they will not be applied by the slave. The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example: STOP SLAVE; CHANGE MASTER TO IGNORE_DOMAIN_IDS = (1,2); START SLAVE; If you would like to clear a previously set list, then you can set the value to an empty list. For example: STOP SLAVE; CHANGE MASTER TO IGNORE_DOMAIN_IDS = (); START SLAVE; The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the IGNORE_DOMAIN_IDS option, and the DO_DOMAIN_IDS option was previously set, then you need to clear the value of the DO_DOMAIN_IDS option. For example: STOP SLAVE; CHANGE MASTER TO DO_DOMAIN_IDS = (), IGNORE_DOMAIN_IDS = (1,2); START SLAVE; The IGNORE_DOMAIN_IDS option can only be specified if the slave is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no in order to use this option. Delayed Replication Options MASTER_DELAY The MASTER_DELAY option for CHANGE MASTER was first added in MariaDB 10.2.3 to enable delayed replication. The MASTER_DELAY option for CHANGE MASTER can be used to enable delayed replication. This option specifies the time in seconds (at least) that a replication slave should lag behind the master. Before executing an event, the slave will first wait, if necessary, until the given time has passed since the event was created on the master. The result is that the slave will reflect the state of the master some time back in the past. The default is zero, no delay. STOP SLAVE; CHANGE MASTER TO MASTER_DELAY=3600; START SLAVE; Changing Option Values If you don't specify a given option when executing the CHANGE MASTER statement, then the option keeps its old value in most cases. Most of the time, there is no need to specify the options that do not need to change. For example, if the password for the user account that the slave uses to connect to its master has changed, but no other options need to change, then you can just change the MASTER_PASSWORD option by executing the following commands: STOP SLAVE; CHANGE MASTER TO MASTER_PASSWORD='new3cret'; START SLAVE; There are some cases where options are implicitly reset, such as when the MASTER_HOST and MASTER_PORT options are changed. Option Persistence The values of the MASTER_LOG_FILE and MASTER_LOG_POS options (i.e. the binary log position on the master) and most other options are written to either the default master.info file or the file that is configured by the master_info_file option. The slave's I/O thread keeps this binary log position updated as it downloads events only when MASTER_USE_GTID option is set to NO. Otherwise the file is not updated on a per event basis. The master_info_file option can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example: [mariadb] ... master_info_file=/mariadb/myserver1-master.info The values of the RELAY_LOG_FILE and RELAY_LOG_POS options (i.e. the relay log position) are written to either the default relay-log.info file or the file that is configured by the relay_log_info_file system variable. The slave's SQL thread keeps this relay log  ;`!COMMITThe COMMIT statement ends a transaction, saving any changes to the data so that they become visible to subsequent transactions. Also, unlocks metadata changed by current transaction. If autocommit is set to 1, an implicit commit is performed after each statement. Otherwise, all transactions which don't end with an explicit COMMIT are implicitly rollbacked and the changes are lost. The ROLLBACK statement can be used to do this explicitly. The required syntax for the COMMIT statement is as follows: COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE] COMMIT is the more important transaction terminator, as well as the more interesting one. The basic form of the COMMIT statement is simply the keyword COMMIT (the keyword WORK is simply noise and can be omitted without changing the effect). The optional AND CHAIN clause is a convenience for initiating a new transaction as soon as the old transaction terminates. If AND CHAIN is specified, then there is effectively nothing between the old and new transactions, although they remain separate. The characteristics of the new transaction will be the same as the characteristics of the old one — that is, the new transaction will have the same access mode, isolation level and diagnostics area size (we'll discuss all of these shortly) as the transaction just terminated. RELEASE tells the server to disconnect the client immediately after the current transaction. There are NO RELEASE and AND NO CHAIN options. By default, commits do not RELEASE or CHAIN, but it's possible to change this default behavior with the completion_type server system variable. In this case, the AND NO CHAIN and NO RELEASE options override the server default. URL: https://mariadb.com/kb/en/commit/https://mariadb.com/kb/en/commit/ae=DEALLOCATE / DROP PREPARESyntax ------ {DEALLOCATE | DROP} PREPARE stmt_name Description ----------- To deallocate a prepared statement produced with PREPARE, use a DEALLOCATE PREPARE statement that refers to the prepared statement name. A prepared statement is implicitly deallocated when a new PREPARE command is issued. In that case, there is no need to use DEALLOCATE. Attempting to execute a prepared statement after deallocating it results in an error, as if it was not prepared at all: ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to EXECUTE If the specified statement has not been PREPAREd, an error similar to the following will be produced: ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to DEALLOCATE PREPARE Example See example in PREPARE. URL: https://mariadb.com/kb/en/deallocate-drop-prepared-statement/https://mariadb.com/kb/en/deallocate-drop-prepared-statement/bs,EXECUTE StatementSyntax ------ EXECUTE stmt_name [USING expression[, expression] ...] EXECUTE with expression as parameters was introduced in MariaDB 10.2.3. Before that one could only use variables (@var_name) as parameters. Description ----------- After preparing a statement with PREPARE, you execute it with an EXECUTE statement that refers to the prepared statement name. If the prepared statement contains any parameter markers, you must supply a USING clause that lists user variables containing the values to be bound to the parameters. Parameter values can be supplied only by user variables, and the USING clause must name exactly as many variables as the number of parameter markers in the statement. You can execute a given prepared statement multiple times, passing different variables to it or setting the variables to different values before each execution. If the specified statement has not been PREPAREd, an error similar to the following is produced: ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to EXECUTE Example See example in PREPARE. URL: https://mariadb.com/kb/en/execute-statement/https://mariadb.com/kb/en/execute-statement/f $SAVEPOINTSyntax ------ SAVEPOINT identifier ROLLBACK [WORK] TO [SAVEPOINT] identifier RELEASE SAVEPOINT identifier Description ----------- InnoDB supports the SQL statements SAVEPOINT, ROLLBACK TO SAVEPOINT, RELEASE SAVEPOINT and the optional WORK keyword for ROLLBACK. Each savepoint must have a legal MariaDB identifier. A savepoint is a named sub-transaction. Normally ROLLBACK undoes the changes performed by the whole transaction. When used with the TO clause, it undoes the changes performed after the specified savepoint, and erases all subsequent savepoints. However, all locks that have been acquired after the save point will survive. RELEASE SAVEPOINT does not rollback or commit any changes, but removes the specified savepoint. When the execution of a trigger or a stored function begins, it is not possible to use statements which reference a savepoint which was defined from out of that stored program. When a COMMIT (including implicit commits) or a ROLLBACK statement (with no TO clause) is performed, they act on the whole transaction, and all savepoints are removed. Errors If COMMIT or ROLLBACK is issued and no transaction was started, no error is reported. If SAVEPOINT is issued and no transaction was started, no error is reported but no savepoint is created. When ROLLBACK TO SAVEPOINT or RELEASE SAVEPOINT is called for a savepoint that does not exist, an error like this is issued: ERROR 1305 (42000): SAVEPOINT svp_name does not exist URL: https://mariadb.com/kb/en/savepoint/https://mariadb.com/kb/en/savepoint/@ yz GRANT ST_XSyntax ------ ST_X(p) X(p) Description ----------- Returns the X-coordinate value for the point p as a double-precision number. ST_X() and X() are synonyms. Examples -------- SET @pt = 'Point(56.7 53.34)'; SELECT X(GeomFromText(@pt)); +----------------------+ | X(GeomFromText(@pt)) | +----------------------+ | 56.7 | +----------------------+ URL: https://mariadb.com/kb/en/st_x/https://mariadb.com/kb/en/st_x/ ST_YSyntax ------ ST_Y(p) Y(p) Description ----------- Returns the Y-coordinate value for the point p as a double-precision number. ST_Y() and Y() are synonyms. Examples -------- SET @pt = 'Point(56.7 53.34)'; SELECT Y(GeomFromText(@pt)); +----------------------+ | Y(GeomFromText(@pt)) | +----------------------+ | 53.34 | +----------------------+ URL: https://mariadb.com/kb/en/st_y/https://mariadb.com/kb/en/st_y/X- XA synonym for ST_X. URL: https://mariadb.com/kb/en/point-properties-x/https://mariadb.com/kb/en/point-properties-x/X- YA synonym for ST_Y. URL: https://mariadb.com/kb/en/point-properties-y/https://mariadb.com/kb/en/point-properties-y/ +& AES_DECRYPTSyntax ------ AES_DECRYPT(crypt_str,key_str) Description ----------- This function allows decryption of data using the official AES (Advanced Encryption Standard) algorithm. For more information, see the description of AES_ENCRYPT(). URL: https://mariadb.com/kb/en/aes_decrypt/https://mariadb.com/kb/en/aes_decrypt/I! DECODESyntax ------ DECODE(crypt_str,pass_str) Description ----------- Decrypts the encrypted string crypt_str using pass_str as the password. crypt_str should be a string returned from ENCODE(). The resulting string will be the original string only if pass_str is the same. URL: https://mariadb.com/kb/en/decode/https://mariadb.com/kb/en/decode/~j"8  qI,c\,EXECUTE IMMEDIATEEXECUTE IMMEDIATE was introduced in MariaDB 10.2.3. Syntax ------ EXECUTE IMMEDIATE statement Description ----------- EXECUTE IMMEDIATE executes a dynamic SQL statement created on the fly, which can reduce performance overhead. For example: EXECUTE IMMEDIATE 'SELECT 1' which is shorthand for: prepare stmt from "select 1"; execute stmt; deallocate prepare stmt; EXECUTE IMMEDIATE supports complex expressions as prepare source and parameters: EXECUTE IMMEDIATE CONCAT('SELECT COUNT(*) FROM ', 't1', ' WHERE a=?') USING 5+5; Limitations: subselects and stored function calls are not supported as a prepare source. The following examples return an error: CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN 'SELECT * FROM t1'; EXECUTE IMMEDIATE f1(); ERROR 1970 (42000): EXECUTE IMMEDIATE does not support subqueries or stored functions EXECUTE IMMEDIATE (SELECT 'SELECT * FROM t1'); ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'SELECT 'SELECT * FROM t1')' at line 1 CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10; EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING f1(); ERROR 1970 (42000): EXECUTE..USING does not support subqueries or stored functions EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING (SELECT 10); ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'SELECT 10)' at line 1 One can use a user or an SP variable as a workaround: CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN 'SELECT * FROM t1'; SET @stmt=f1(); EXECUTE IMMEDIATE @stmt; SET @stmt=(SELECT 'SELECT 1'); EXECUTE IMMEDIATE @stmt; CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10; SET @param=f1(); EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING @param; SET @param=(SELECT 10); EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING @param; EXECUTE IMMEDIATE supports user variables and SP variables as OUT parameters DELIMITER $$ CREATE OR REPLACE PROCEDURE p1(OUT a INT) BEGIN SET a:= 10; END; $$ DELIMITER ; SET @a=2; EXECUTE IMMEDIATE 'CALL p1(?)' USING @a; SELECT @a; +------+ | @a | +------+ | 10 | +------+ Similar to PREPARE, EXECUTE IMMEDIATE is allowed in stored procedures but is not allowed in stored functions. This example uses EXECUTE IMMEDIATE inside a stored procedure: DELIMITER $$ CREATE OR REPLACE PROCEDURE p1() BEGIN EXECUTE IMMEDIATE 'SELECT 1'; END; $$ DELIMITER ; CALL p1; +---+ | 1 | +---+ | 1 | +---+ This script returns an error: DELIMITER $$ CREATE FUNCTION f1() RETURNS INT BEGIN EXECUTE IMMEDIATE 'DO 1'; RETURN 1; END; $$ ERROR 1336 (0A000): Dynamic SQL is not allowed in stored function or trigger EXECUTE IMMEDIATE can use DEFAULT and IGNORE indicators as bind parameters: CREATE OR REPLACE TABLE t1 (a INT DEFAULT 10); EXECUTE IMMEDIATE 'INSERT INTO t1 VALUES (?)' USING DEFAULT; SELECT * FROM t1; +------+ | a | +------+ | 10 | +------+ EXECUTE IMMEDIATE increments the Com_execute_immediate status variable, as well as the Com_stmt_prepare, Com_stmt_execute and Com_stmt_close status variables. Note, EXECUTE IMMEDIATE does not increment the Com_execute_sql status variable. Com_execute_sql is used only for PREPARE..EXECUTE. This session screenshot demonstrates how EXECUTE IMMEDIATE affects status variables: SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME RLIKE ('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)'); +-----------------------+----------------+ | VARIABLE_NAME | VARIABLE_VALUE | +-----------------------+----------------+ | COM_EXECUTE_IMMEDIATE | 0 | | COM_EXECUTE_SQL | 0 | | COM_STMT_CLOSE | 0 | | COM_STMT_EXECUTE | 0 | | COM_STMT_PREPARE | 0 | +-----------------------+----------------+ EXECUTE IMMEDIATE 'SELECT 1'; +---+ | 1 | +---+ | 1 | +---+ SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME RLIKE ('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)'); +-----------------------+----------------+ | VARIABLE_NAME | VARIABLE_VALUE | +-----------------------+----------------+ | COM_EXECUTE_IMMEDIATE | 1 | | COM_EXECUTE_SQL | 0 | | COM_STMT_CLOSE | 1 | | COM_STMT_EXECUTE | 1 | | COM_STMT_PREPARE | 1 | +-----------------------+----------------+ URL: https://mariadb.com/kb/en/execute-immediate/https://mariadb.com/kb/en/execute-immediate/g+Metadata LockingMetadata locking has been supported since MariaDB 5.5. This means that when a transaction (including XA transactions) uses a table, it locks its metadata until the end of transaction. Non-transactional tables are also locked, as well as views and objects which are related to locked tables/views (stored functions, triggers, etc). When a connection tries to use a DDL statement (like an ALTER TABLE) which modifies a table that is locked, that connection is queued, and has to wait until it's unlocked. Using savepoints and performing a partial rollback does not release metadata locks. LOCK TABLES ... WRITE are also queued. Some wrong statements which produce an error may not need to wait for the lock to be freed. Metadata lock's timeout is determined by the value of the lock_wait_timeout server system variable (in seconds). However, note that its default value is 31536000 (1 year). If this timeout exceeds, the following error is returned: ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction If the metadata_lock_info plugin is installed, the Information Schema metadata_lock_info table stores information about existing metadata locks. Example Let's use the following MEMORY (non-transactional) table: CREATE TABLE t (a INT) ENGINE = MEMORY; Connection 1 starts a transaction, and INSERTs a row into t: START TRANSACTION; INSERT INTO t SET a=1; t's metadata is now locked by connection 1. Connection 2 tries to alter t, but has to wait: ALTER TABLE t ADD COLUMN b INT; Connection 2's prompt is blocked now. Now connection 1 ends the transaction: COMMIT; ...and connection 2 finally gets the output of its command: Query OK, 1 row affected (35.23 sec) Records: 1 Duplicates: 0 Warnings: 0 URL: https://mariadb.com/kb/en/metadata-locking/https://mariadb.com/kb/en/metadata-locking/ MD5Syntax ------ MD5(str) Description ----------- Calculates an MD5 128-bit checksum for the string. The return value is a 32-hex digit string, and as of MariaDB 5.5, is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string. NULL is returned if the argument was NULL. Examples -------- SELECT MD5('testing'); +----------------------------------+ | MD5('testing') | +----------------------------------+ | ae2b1fca515949e5d54fb22b8ed95575 | +----------------------------------+ URL: https://mariadb.com/kb/en/md5/https://mariadb.com/kb/en/md5/# PASSWORDSyntax ------ PASSWORD(str) Description ----------- The PASSWORD() function is used for hashing passwords for use in authentication by the MariaDB server. It is not intended for use in other applications. Calculates and returns a hashed password string from the plaintext password str. Returns an empty string (>= MariaDB 10.0.4) or NULL ( URL: https://mariadb.com/kb/en/password/https://mariadb.com/kb/en/password/f Ѧ2d &LOCK TABLESSyntax ------ LOCK TABLE[S] tbl_name [[AS] alias] lock_type [, tbl_name [[AS] alias] lock_type] ... [WAIT n|NOWAIT] lock_type: READ [LOCAL] | [LOW_PRIORITY] WRITE | WRITE CONCURRENT UNLOCK TABLES Description ----------- The lock_type can be one of: Option | Description | READ | Read lock, no writes allowed | READ LOCAL | Read lock, but allow concurrent inserts | WRITE | Exclusive write lock. No other connections can read or write to this table | LOW_PRIORITY WRITE | Exclusive write lock, but allow new read locks on the table until we get the write lock. | WRITE CONCURRENT | Exclusive write lock, but allow READ LOCAL locks to the table. | MariaDB enables client sessions to acquire table locks explicitly for the purpose of cooperating with other sessions for access to tables, or to prevent other sessions from modifying tables during periods when a session requires exclusive access to them. A session can acquire or release locks only for itself. One session cannot acquire locks for another session or release locks held by another session. Locks may be used to emulate transactions or to get more speed when updating tables. LOCK TABLES explicitly acquires table locks for the current client session. Table locks can be acquired for base tables or views. To use LOCK TABLES, you must have the LOCK TABLES privilege, and the SELECT privilege for each object to be locked. See GRANT For view locking, LOCK TABLES adds all base tables used in the view to the set of tables to be locked and locks them automatically. If you lock a table explicitly with LOCK TABLES, any tables used in triggers are also locked implicitly, as described in Triggers and Implicit Locks. UNLOCK TABLES explicitly releases any table locks held by the current session. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. Limitations LOCK TABLES doesn't work when using Galera cluster. You may experience crashes or locks when used with Galera. LOCK TABLES works on XtraDB/InnoDB tables only if the innodb_table_locks system variable is set to 1 (the default) and autocommit is set to 0 (1 is default). Please note that no error message will be returned on LOCK TABLES with innodb_table_locks = 0. LOCK TABLES implicitly commits the active transaction, if any. Also, starting a transaction always releases all table locks acquired with LOCK TABLES. This means that there is no way to have table locks and an active transaction at the same time. The only exceptions are the transactions in autocommit mode. To preserve the data integrity between transactional and non-transactional tables, the GET_LOCK() function can be used. While a connection holds an explicit read lock on a table, it cannot modify it. If you try, the following error will be produced: ERROR 1099 (HY000): Table 'tab_name' was locked with a READ lock and can't be updated While a connection holds an explicit lock on a table, it cannot access a non-locked table. If you try, the following error will be produced: ERROR 1100 (HY000): Table 'tab_name' was not locked with LOCK TABLES While a connection holds an explicit lock on a table, it cannot issue the following: INSERT DELAYED, CREATE TABLE, CREATE TABLE ... LIKE, and DDL statements involving stored programs and views (except for triggers). If you try, the following error will be produced: ERROR 1192 (HY000): Can't execute the given command because you have active locked tables or an active transaction LOCK TABLES can not be used in stored routines - if you try, the following error will be produced on creation: ERROR 1314 (0A000): LOCK is not allowed in stored procedures URL: https://mariadb.com/kb/en/lock-tables/https://mariadb.com/kb/en/lock-tables/i,PURGE BINARY LOGSSyntax ------ PURGE { BINARY | MASTER } LOGS { TO 'log_name' | BEFORE datetime_expr } Description ----------- The PURGE BINARY LOGS statement deletes all the binary log files listed in the log index file prior to the specified log file name or date. BINARY and MASTER are synonyms. Deleted log files also are removed from the list recorded in the index file, so that the given log file becomes the first in the list. The datetime expression is in the format 'YYYY-MM-DD hh:mm:ss'. If a slave is active but has yet to read from a binary log file you attempt to delete, the statement will fail with an error. However, if the slave is not connected and has yet to read from a log file you delete, the file will be deleted, but the slave will be unable to continue replicating once it connects again. This statement has no effect if the server was not started with the --log-bin option to enable binary logging. To list the binary log files on the server, use SHOW BINARY LOGS. To see which files they are reading, use SHOW SLAVE STATUS. You can only delete the files that are older than the oldest file that is used by the slaves. To delete all binary log files, use RESET MASTER. To move to a new log file (for example if you want to remove the current log file), use FLUSH LOGS before you execute PURGE LOGS. If the expire_logs_days server system variable is not set to 0, the server automatically deletes binary log files after the given number of days. Examples -------- PURGE BINARY LOGS TO 'mariadb-bin.000063'; PURGE BINARY LOGS BEFORE '2013-04-21'; PURGE BINARY LOGS BEFORE '2013-04-22 09:55:22'; URL: https://mariadb.com/kb/en/purge-binary-logs/https://mariadb.com/kb/en/purge-binary-logs/k9 ENDPOINTA synonym for ST_ENDPOINT. URL: https://mariadb.com/kb/en/linestring-properties-endpoint/https://mariadb.com/kb/en/linestring-properties-endpoint/" GLENGTHSyntax ------ GLength(ls) Description ----------- Returns as a double-precision number the length of the LineString value ls in its associated spatial reference. Examples -------- SET @ls = 'LineString(1 1,2 2,3 3)'; SELECT GLength(GeomFromText(@ls)); +----------------------------+ | GLength(GeomFromText(@ls)) | +----------------------------+ | 2.82842712474619 | +----------------------------+ URL: https://mariadb.com/kb/en/glength/https://mariadb.com/kb/en/glength/ m: NumPointsA synonym for ST_NumPoints. URL: https://mariadb.com/kb/en/linestring-properties-numpoints/https://mariadb.com/kb/en/linestring-properties-numpoints/g7 PointNA synonym for ST_PointN. URL: https://mariadb.com/kb/en/linestring-properties-pointn/https://mariadb.com/kb/en/linestring-properties-pointn/ o; STARTPOINTA synonym for ST_STARTPOINT. URL: https://mariadb.com/kb/en/linestring-properties-startpoint/https://mariadb.com/kb/en/linestring-properties-startpoint/ & ST_ENDPOINTSyntax ------ ST_EndPoint(ls) EndPoint(ls) Description ----------- Returns the Point that is the endpoint of the LineString value ls. ST_EndPoint() and EndPoint() are synonyms. Examples -------- SET @ls = 'LineString(1 1,2 2,3 3)'; SELECT AsText(EndPoint(GeomFromText(@ls))); +-------------------------------------+ | AsText(EndPoint(GeomFromText(@ls))) | +-------------------------------------+ | POINT(3 3) | +-------------------------------------+ URL: https://mariadb.com/kb/en/st_endpoint/https://mariadb.com/kb/en/st_endpoint/JZb `eT #ROLLBACKThe ROLLBACK statement rolls back (ends) a transaction, destroying any changes to SQL-data so that they never become visible to subsequent transactions. The required syntax for the ROLLBACK statement is as follows. ROLLBACK [ WORK ] [ AND [ NO ] CHAIN ] [ TO [ SAVEPOINT ] { | } ] The ROLLBACK statement will either end a transaction, destroying all data changes that happened during any of the transaction, or it will just destroy any data changes that happened since you established a savepoint. The basic form of the ROLLBACK statement is just the keyword ROLLBACK (the keyword WORK is simply noise and can be omitted without changing the effect). The optional AND CHAIN clause is a convenience for initiating a new transaction as soon as the old transaction terminates. If AND CHAIN is specified, then there is effectively nothing between the old and new transactions, although they remain separate. The characteristics of the new transaction will be the same as the characteristics of the old one — that is, the new transaction will have the same access mode, isolation level and diagnostics area size (we'll discuss all of these shortly) as the transaction just terminated. The AND NO CHAIN option just tells your DBMS to end the transaction — that is, these four SQL statements are equivalent: ROLLBACK; ROLLBACK WORK; ROLLBACK AND NO CHAIN; ROLLBACK WORK AND NO CHAIN; All of them end a transaction without saving any transaction characteristics. The only other options, the equivalent statements: ROLLBACK AND CHAIN; ROLLBACK WORK AND CHAIN; both tell your DBMS to end a transaction, but to save that transaction's characteristics for the next transaction. ROLLBACK is much simpler than COMMIT: it may involve no more than a few deletions (of Cursors, locks, prepared SQL statements and log-file entries). It's usually assumed that ROLLBACK can't fail, although such a thing is conceivable (for example, an encompassing transaction might reject an attempt to ROLLBACK because it's lining up for a COMMIT). ROLLBACK cancels all effects of a transaction. It does not cancel effects on objects outside the DBMS's control (for example the values in host program variables or the settings made by some SQL/CLI function calls). But in general, it is a convenient statement for those situations when you say "oops, this isn't working" or when you simply don't care whether your temporary work becomes permanent or not. Here is a moot question. If all you've been doing is SELECTs, so that there have been no data changes, should you end the transaction with ROLLBACK or COMMIT? It shouldn't really matter because both ROLLBACK and COMMIT do the same transaction-terminating job. However, the popular conception is that ROLLBACK implies failure, so after a successful series of SELECT statements the convention is to end the transaction with COMMIT rather than ROLLBACK. MariaDB (and most other DBMSs) supports rollback of SQL-data change statements, but not of SQL-Schema statements. This means that if you use any of CREATE, ALTER, DROP, GRANT, REVOKE, you are implicitly committing at execution time. INSERT INTO Table_2 VALUES(5); DROP TABLE Table_3 CASCADE; ROLLBACK; The result will be that both the INSERT and the DROP will go through as separate transactions so the ROLLBACK will have no effect. URL: https://mariadb.com/kb/en/rollback/https://mariadb.com/kb/en/rollback/k 6RESET SLAVERESET SLAVE ["connection_name"] [ALL] RESET SLAVE makes the slave forget its replication position in the master's binary log. This statement is meant to be used for a clean start. It deletes the master.info and relay-log.info files, all the relay log files, and starts a new relay log file. To use RESET SLAVE, the slave replication threads must be stopped (use STOP SLAVE if necessary). Note: All relay log files are deleted, even if they have not been completely executed by the slave SQL thread. (This is a condition likely to exist on a replication slave if you have issued a STOP SLAVE statement or if the slave is highly loaded.) Connection information stored in the master.info file is immediately reset using any values specified in the corresponding startup options. This information includes values such as master host, master port, master user, and master password. If the slave SQL thread was in the middle of replicating temporary tables when it was stopped, and RESET SLAVE is issued, these replicated temporary tables are deleted on the slave. The ALL also resets the PORT, HOST, USER and PASSWORD parameters for the slave. If you are using a connection name, it will permanently delete it and it will not show up anymore in SHOW ALL SLAVES STATUS. connection_name The connection_name option was added as part of multi-source replication added in MariaDB 10.0 If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the RESET SLAVE statement will apply to the specified master. connection_name is case-insensitive. URL: https://mariadb.com/kb/en/reset-slave-connection_name/https://mariadb.com/kb/en/reset-slave-connection_name/ ' ST_NUMPOINTSSyntax ------ ST_NumPoints(ls) NumPoints(ls) Description ----------- Returns the number of Point objects in the LineString value ls. ST_NumPoints() and NumPoints() are synonyms. Examples -------- SET @ls = 'LineString(1 1,2 2,3 3)'; SELECT NumPoints(GeomFromText(@ls)); +------------------------------+ | NumPoints(GeomFromText(@ls)) | +------------------------------+ | 3 | +------------------------------+ URL: https://mariadb.com/kb/en/st_numpoints/https://mariadb.com/kb/en/st_numpoints/ $ ST_POINTNSyntax ------ ST_PointN(ls,N) PointN(ls,N) Description ----------- Returns the N-th Point in the LineString value ls. Points are numbered beginning with 1. ST_PointN() and PointN() are synonyms. Examples -------- SET @ls = 'LineString(1 1,2 2,3 3)'; SELECT AsText(PointN(GeomFromText(@ls),2)); +-------------------------------------+ | AsText(PointN(GeomFromText(@ls),2)) | +-------------------------------------+ | POINT(2 2) | +-------------------------------------+ URL: https://mariadb.com/kb/en/st_pointn/https://mariadb.com/kb/en/st_pointn/ U$INET_ATONSyntax ------ INET_ATON(expr) Description ----------- Given the dotted-quad representation of an IPv4 network address as a string, returns an integer that represents the numeric value of the address. Addresses may be 4- or 8-byte addresses. Returns NULL if the argument is not understood. Examples -------- SELECT INET_ATON('192.168.1.1'); +--------------------------+ | INET_ATON('192.168.1.1') | +--------------------------+ | 3232235777 | +--------------------------+ This is calculated as follows: 192 x 2563 + 168 x 256 2 + 1 x 256 + 1 URL: https://mariadb.com/kb/en/inet_aton/https://mariadb.com/kb/en/inet_aton/ $INET_NTOASyntax ------ INET_NTOA(expr) Description ----------- Given a numeric IPv4 network address in network byte order (4 or 8 byte), returns the dotted-quad representation of the address as a string. Examples -------- SELECT INET_NTOA(3232235777); +-----------------------+ | INET_NTOA(3232235777) | +-----------------------+ | 192.168.1.1 | +-----------------------+ 192.168.1.1 corresponds to 3232235777 since 192 x 2563 + 168 x 256 2 + 1 x 256 + 1 = 3232235777 URL: https://mariadb.com/kb/en/inet_ntoa/https://mariadb.com/kb/en/inet_ntoa/<&V"  ]Yh,PREPARE StatementSyntax ------ PREPARE stmt_name FROM preparable_stmt Description ----------- The PREPARE statement prepares a statement and assigns it a name, stmt_name, by which to refer to the statement later. Statement names are not case sensitive. preparable_stmt is either a string literal or a user variable (not a local variable, an SQL expression or a subquery) that contains the text of the statement. The text must represent a single SQL statement, not multiple statements. Within the statement, "?" characters can be used as parameter markers to indicate where data values are to be bound to the query later when you execute it. The "?" characters should not be enclosed within quotes, even if you intend to bind them to string values. Parameter markers can be used only where data values should appear, not for SQL keywords, identifiers, and so forth. The scope of a prepared statement is the session within which it is created. Other sessions cannot see it. If a prepared statement with the given name already exists, it is deallocated implicitly before the new statement is prepared. This means that if the new statement contains an error and cannot be prepared, an error is returned and no statement with the given name exists. Prepared statements can be PREPAREd and EXECUTEd in a stored procedure, but not in a stored function or trigger. Also, even if the statement is PREPAREd in a procedure, it will not be deallocated when the procedure execution ends. A prepared statement can access user-defined variables, but not local variables or procedure's parameters. If the prepared statement contains a syntax error, PREPARE will fail. As a side effect, stored procedures can use it to check if a statement is valid. For example: CREATE PROCEDURE `test_stmt`(IN sql_text TEXT) BEGIN DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN SELECT CONCAT(sql_text, ' is not valid'); END; SET @SQL := sql_text; PREPARE stmt FROM @SQL; DEALLOCATE PREPARE stmt; END; The FOUND_ROWS() and ROW_COUNT() functions, if called immediatly after EXECUTE, return the number of rows read or affected by the prepared statements; however, if they are called after DEALLOCATE PREPARE, they provide information about this statement. If the prepared statement produces errors or warnings, GET DIAGNOSTICS return information about them. DEALLOCATE PREPARE shouldn't clear the diagnostics area, unless it produces an error. A prepared statement is executed with EXECUTE and released with DEALLOCATE PREPARE. The max_prepared_stmt_count server system variable determines the number of allowed prepared statements that can be prepared on the server. If it is set to 0, prepared statements are not allowed. If the limit is reached, an error similar to the following will be produced: ERROR 1461 (42000): Can't create more than max_prepared_stmt_count statements (current value: 0) Oracle Mode In Oracle mode from MariaDB 10.3, PREPARE stmt FROM 'SELECT :1, :2' is used, instead of ?. Permitted Statements Not all statements can be prepared. Only the following SQL commands are permitted: ALTER TABLE ANALYZE TABLE BINLOG CACHE INDEX CALL CHANGE MASTER CHECKSUM {TABLE | TABLES} COMMIT {CREATE | DROP} DATABASE {CREATE | DROP} INDEX {CREATE | RENAME | DROP} TABLE {CREATE | RENAME | DROP} USER {CREATE | DROP} VIEW DELETE DESCRIBE DO EXPLAIN FLUSH {TABLE | TABLES | TABLES WITH READ LOCK | HOSTS | PRIVILEGES | LOGS | STATUS | MASTER | SLAVE | DES_KEY_FILE | USER_RESOURCES | QUERY CACHE | TABLE_STATISTICS | INDEX_STATISTICS | USER_STATISTICS | CLIENT_STATISTICS} GRANT INSERT INSTALL {PLUGIN | SONAME} HANDLER READ KILL LOAD INDEX INTO CACHE OPTIMIZE TABLE REPAIR TABLE REPLACE RESET {MASTER | SLAVE | QUERY CACHE} REVOKE ROLLBACK SELECT SET SET GLOBAL SQL_SLAVE_SKIP_COUNTER SET ROLE SET SQL_LOG_BIN SET TRANSACTION ISOLATION LEVEL SHOW EXPLAIN SHOW {DATABASES | TABLES | OPEN TABLES | TABLE STATUS | COLUMNS | INDEX | TRIGGERS | EVENTS | GRANTS | CHARACTER SET | COLLATION | ENGINES | PLUGINS [SONAME] | PRIVILEGES | PROCESSLIST | PROFILE | PROFILES | VARIABLES | STATUS | WARNINGS | ERRORS | TABLE_STATISTICS | INDEX_STATISTICS | USER_STATISTICS | CLIENT_STATISTICS | AUTHORS | CONTRIBUTORS} SHOW CREATE {DATABASE | TABLE | VIEW | PROCEDURE | FUNCTION | TRIGGER | EVENT} SHOW {FUNCTION | PROCEDURE} CODE SHOW BINLOG EVENTS SHOW SLAVE HOSTS SHOW {MASTER | BINARY} LOGS SHOW {MASTER | SLAVE | TABLES | INNODB | FUNCTION | PROCEDURE} STATUS SLAVE {START | STOP} TRUNCATE TABLE SHUTDOWN UNINSTALL {PLUGIN | SONAME} UPDATE Synonyms are not listed here, but can be used. For example, DESC can be used instead of DESCRIBE. Compound statements can be prepared too. Note that if a statement can be run in a stored routine, it will work even if it is called by a prepared statement. For example, SIGNAL can't be directly prepared. However, it is allowed in stored routines. If the x() procedure contains SIGNAL, you can still prepare and execute the 'CALL x();' prepared statement. PREPARE now supports most kinds of expressions as well, for example: PREPARE stmt FROM CONCAT('SELECT * FROM ', table_name); When PREPARE is used with a statement which is not supported, the following error is produced: ERROR 1295 (HY000): This command is not supported in the prepared statement protocol yet Example create table t1 (a int,b char(10)); insert into t1 values (1,"one"),(2, "two"),(3,"three"); prepare test from "select * from t1 where a=?"; set @param=2; execute test using @param; +------+------+ | a | b | +------+------+ | 2 | two | +------+------+ set @param=3; execute test using @param; +------+-------+ | a | b | +------+-------+ | 3 | three | +------+-------+ deallocate prepare test; Since identifiers are not permitted as prepared statements parameters, sometimes it is necessary to dynamically compose an SQL statement. This technique is called dynamic SQL). The following example shows how to use dynamic SQL: CREATE PROCEDURE test.stmt_test(IN tab_name VARCHAR(64)) BEGIN SET @sql = CONCAT('SELECT COUNT(*) FROM ', tab_name); PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt; END; CALL test.stmt_test('mysql.user'); +----------+ | COUNT(*) | +----------+ | 4 | +----------+ Use of variables in prepared statements: PREPARE stmt FROM 'SELECT @x;'; SET @x = 1; EXECUTE stmt; +------+ | @x | +------+ | 1 | +------+ SET @x = 0; EXECUTE stmt; +------+ | @x | +------+ | 0 | +------+ DEALLOCATE PREPARE stmt; URL: https://mariadb.com/kb/en/prepare-statement/https://mariadb.com/kb/en/prepare-statement/ u'IS_FREE_LOCKSyntax ------ IS_FREE_LOCK(str) Description ----------- Checks whether the lock named str is free to use (that is, not locked). Returns 1 if the lock is free (no one is using the lock), 0 if the lock is in use, and NULL if an error occurs (such as an incorrect argument, like an empty string or NULL). str is case insensitive. If the metadata_lock_info plugin is installed, the Information Schema metadata_lock_info table contains information about locks of this kind (as well as metadata locks). Statements using the IS_FREE_LOCK() function are not safe for replication. URL: https://mariadb.com/kb/en/is_free_lock/https://mariadb.com/kb/en/is_free_lock/"IS_IPV6IS_IPV6() has been available since MariaDB 10.0.12. Syntax ------ IS_IPV6(expr) Description ----------- Returns 1 if the expression is a valid IPv6 address specified as a string, otherwise returns 0. Does not consider IPv4 addresses to be valid IPv6 addresses. Examples -------- SELECT IS_IPV6('48f3::d432:1431:ba23:846f'); +--------------------------------------+ | IS_IPV6('48f3::d432:1431:ba23:846f') | +--------------------------------------+ | 1 | +--------------------------------------+ 1 row in set (0.02 sec) SELECT IS_IPV6('10.0.1.1'); +---------------------+ | IS_IPV6('10.0.1.1') | +---------------------+ | 0 | +---------------------+ URL: https://mariadb.com/kb/en/is_ipv6/https://mariadb.com/kb/en/is_ipv6/ Bl2*SET TRANSACTIONSyntax ------ SET [GLOBAL | SESSION] TRANSACTION transaction_property [, transaction_property] ... transaction_property: ISOLATION LEVEL level | READ WRITE | READ ONLY level: REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED | SERIALIZABLE Description ----------- This statement sets the transaction isolation level or the transaction access mode globally, for the current session, or for the next transaction: With the GLOBAL keyword, the statement sets the default transaction level globally for all subsequent sessions. Existing sessions are unaffected. With the SESSION keyword, the statement sets the default transaction level for all subsequent transactions performed within the current session. Without any SESSION or GLOBAL keyword, the statement sets the isolation level for the next (not started) transaction performed within the current session. A change to the global default isolation level requires the SUPER privilege. Any session is free to change its session isolation level (even in the middle of a transaction), or the isolation level for its next transaction. Isolation Level To set the global default isolation level at server startup, use the --transaction-isolation=level option on the command line or in an option file. Values of level for this option use dashes rather than spaces, so the allowable values are READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. For example, to set the default isolation level to REPEATABLE READ, use these lines in the [mysqld] section of an option file: [mysqld] transaction-isolation = REPEATABLE-READ To determine the global and session transaction isolation levels at runtime, check the value of the tx_isolation system variable: SELECT @@GLOBAL.tx_isolation, @@tx_isolation; InnoDB supports each of the translation isolation levels described here using different locking strategies. The default level is REPEATABLE READ. For additional information about InnoDB record-level locks and how it uses them to execute various types of statements, see XtraDB/InnoDB Lock Modes, and http://dev.mysql.com/doc/refman/en/innodb-locks-set.html. Isolation Levels The following sections describe how MariaDB supports the different transaction levels. READ UNCOMMITTED SELECT statements are performed in a non-locking fashion, but a possible earlier version of a row might be used. Thus, using this isolation level, such reads are not consistent. This is also called a "dirty read." Otherwise, this isolation level works like READ COMMITTED. READ COMMITTED A somewhat Oracle-like isolation level with respect to consistent (non-locking) reads: Each consistent read, even within the same transaction, sets and reads its own fresh snapshot. See http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html. For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), InnoDB locks only index records, not the gaps before them, and thus allows the free insertion of new records next to locked records. For UPDATE and DELETE statements, locking depends on whether the statement uses a unique index with a unique search condition (such as WHERE id = 100), or a range-type search condition (such as WHERE id > 100). For a unique index with a unique search condition, InnoDB locks only the index record found, not the gap before it. For range-type searches, InnoDB locks the index range scanned, using gap locks or next-key (gap plus index-record) locks to block insertions by other sessions into the gaps covered by the range. This is necessary because "phantom rows" must be blocked for MySQL replication and recovery to work. Note: Since MariaDB 5.1, if the READ COMMITTED isolation level is used or the innodb_locks_unsafe_for_binlog system variable is enabled, there is no InnoDB gap locking except for foreign-key constraint checking and duplicate-key checking. Also, record locks for non-matching rows are released after MariaDB has evaluated the WHERE condition. As of MariaDB/MySQL 5.1, if you use READ COMMITTED or enable innodb_locks_unsafe_for_binlog, you must use row-based binary logging. REPEATABLE READ This is the default isolation level for InnoDB. For consistent reads, there is an important difference from the READ COMMITTED isolation level: All consistent reads within the same transaction read the snapshot established by the first read. This convention means that if you issue several plain (non-locking) SELECT statements within the same transaction, these SELECT statements are consistent also with respect to each other. See http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html. For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), UPDATE, and DELETE statements, locking depends on whether the statement uses a unique index with a unique search condition, or a range-type search condition. For a unique index with a unique search condition, InnoDB locks only the index record found, not the gap before it. For other search conditions, InnoDB locks the index range scanned, using gap locks or next-key (gap plus index-record) locks to block insertions by other sessions into the gaps covered by the range. This is the minimum isolation level for non-distributed XA transactions. SERIALIZABLE This level is like REPEATABLE READ, but InnoDB implicitly converts all plain SELECT statements to SELECT ... LOCK IN SHARE MODE if autocommit is disabled. If autocommit is enabled, the SELECT is its own transaction. It therefore is known to be read only and can be serialized if performed as a consistent (non-locking) read and need not block for other transactions. (This means that to force a plain SELECT to block if other transactions have modified the selected rows, you should disable autocommit.) Distributed XA transactions should always use this isolation level. Access Mode These clauses appeared in MariaDB 10.0. The access mode specifies whether the transaction is allowed to write data or not. By default, transactions are in READ WRITE mode (see the tx_read_only system variable). READ ONLY mode allows the storage engine to apply optimizations that cannot be used for transactions which write data. The only exception to this rule is that read only transactions can perform DDL statements on temporary tables. It is not permitted to specify both READ WRITE and READ ONLY in the same statement. READ WRITE and READ ONLY can also be specified in the START TRANSACTION statement, in which case the specified mode is only valid for one transaction. Examples -------- SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE; Attempting to set the isolation level within an existing transaction without specifying GLOBAL or SESSION. START TRANSACTION; SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; ERROR 1568 (25001): Transaction characteristics can't be changed while a transaction is in progress URL: https://mariadb.com/kb/en/set-transaction/https://mariadb.com/kb/en/set-transaction/ ('IS_USED_LOCKSyntax ------ IS_USED_LOCK(str) Description ----------- Checks whether the lock named str is in use (that is, locked). If so, it returns the connection identifier of the client that holds the lock. Otherwise, it returns NULL. str is case insensitive. If the metadata_lock_info plugin is installed, the Information Schema metadata_lock_info table contains information about locks of this kind (as well as metadata locks). Statements using the IS_USED_LOCK() function are not safe for replication. URL: https://mariadb.com/kb/en/is_used_lock/https://mariadb.com/kb/en/is_used_lock/i yBFm &START SLAVESyntax ------ START SLAVE ["connection_name"] [thread_type [, thread_type] ... ] START SLAVE ["connection_name"] [SQL_THREAD] UNTIL MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos START SLAVE ["connection_name"] [SQL_THREAD] UNTIL RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos START SLAVE ["connection_name"] [SQL_THREAD] UNTIL MASTER_GTID_POS = START ALL SLAVES [thread_type [, thread_type]] thread_type: IO_THREAD | SQL_THREAD Description ----------- START SLAVE with no thread_type options starts both of the slave threads (see replication). The I/O thread reads events from the master server and stores them in the relay log. The SQL thread reads events from the relay log and executes them. START SLAVE requires the SUPER privilege. If START SLAVE succeeds in starting the slave threads, it returns without any error. However, even in that case, it might be that the slave threads start and then later stop (for example, because they do not manage to connect to the master or read its binary log, or some other problem). START SLAVE does not warn you about this. You must check the slave's error log for error messages generated by the slave threads, or check that they are running satisfactorily with SHOW SLAVE STATUS. START SLAVE UNTIL START SLAVE UNTIL refers to the SQL_THREAD slave position at which the SQL_THREAD replication will halt. If SQL_THREAD isn't specified both threads are started. Since version 10.0.2, START SLAVE UNTIL master_gtid_pos=xxx has also been supported. See Global Transaction ID/START SLAVE UNTIL master_gtid_pos=xxx for more details. connection_name The connection_name option was added as part of multi-source replication added in MariaDB 10.0 If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the START SLAVE statement will apply to the specified master. connection_name is case-insensitive. START ALL SLAVES START ALL SLAVES starts all configured slaves (slaves with master_host not empty) that were not started before. It will give a note for all started connections. You can check the notes with SHOW WARNINGS. URL: https://mariadb.com/kb/en/start-slave/https://mariadb.com/kb/en/start-slave/nb,START TRANSACTIONSyntax ------ START TRANSACTION [transaction_property [, transaction_property] ...] | BEGIN [WORK] COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE] ROLLBACK [WORK] [AND [NO] CHAIN] [[NO] RELEASE] SET autocommit = {0 | 1} transaction_property: WITH CONSISTENT SNAPSHOT | READ WRITE | READ ONLY Description ----------- The START TRANSACTION or BEGIN statement begins a new transaction. COMMIT commits the current transaction, making its changes permanent. ROLLBACK rolls back the current transaction, canceling its changes. The SET autocommit statement disables or enables the default autocommit mode for the current session. START TRANSACTION and SET autocommit = 1 implicitly commit the current transaction, if any. The optional WORK keyword is supported for COMMIT and ROLLBACK, as are the CHAIN and RELEASE clauses. CHAIN and RELEASE can be used for additional control over transaction completion. The value of the completion_type system variable determines the default completion behavior. The AND CHAIN clause causes a new transaction to begin as soon as the current one ends, and the new transaction has the same isolation level as the just-terminated transaction. The RELEASE clause causes the server to disconnect the current client session after terminating the current transaction. Including the NO keyword suppresses CHAIN or RELEASE completion, which can be useful if the completion_type system variable is set to cause chaining or release completion by default. Access Mode These clauses appeared in MariaDB 10.0. The access mode specifies whether the transaction is allowed to write data or not. By default, transactions are in READ WRITE mode (see the tx_read_only system variable). READ ONLY mode allows the storage engine to apply optimizations that cannot be used for transactions which write data. The only exception to this rule is that read only transactions can perform DDL statements on temporary tables. It is not permitted to specify both READ WRITE and READ ONLY in the same statement. READ WRITE and READ ONLY can also be specified in the SET TRANSACTION statement, in which case the specified mode is valid for all sessions, or for all subsequent transaction used by the current session. autocommit By default, MariaDB runs with autocommit mode enabled. This means that as soon as you execute a statement that updates (modifies) a table, MariaDB stores the update on disk to make it permanent. To disable autocommit mode, use the following statement: SET autocommit=0; After disabling autocommit mode by setting the autocommit variable to zero, changes to transaction-safe tables (such as those for InnoDB or NDBCLUSTER) are not made permanent immediately. You must use COMMIT to store your changes to disk or ROLLBACK to ignore the changes. To disable autocommit mode for a single series of statements, use the START TRANSACTION statement. DDL Statements DDL statements (CREATE, ALTER, DROP) and administrative statements (FLUSH, RESET, OPTIMIZE, ANALYZE, CHECK, REPAIR, CACHE INDEX), and LOAD DATA INFILE, cause an implicit COMMIT and start a new transaction. An exception to this rule are the DDL that operate on temporary tables: you can CREATE, ALTER and DROP them without causing any COMMIT, but those actions cannot be rolled back. This means that if you call ROLLBACK, the temporary tables you created in the transaction will remain, while the rest of the transaction will be rolled back. Transactions cannot be used in Stored Functions or Triggers. In Stored Procedures and Events BEGIN is not allowed, so you should use START TRANSACTION instead. A transaction acquires a metadata lock on every table it accesses to prevent other connections from altering their structure. The lock is released at the end of the transaction. This happens even with non-transactional storage engines (like MEMORY or CONNECT), so it makes sense to use transactions with non-transactional tables. in_transaction The in_transaction system variable appeared in MariaDB 5.3. It is a session-only, read-only variable that returns 1 inside a transaction, and 0 if not in a transaction. WITH CONSISTENT SNAPSHOT The WITH CONSISTENT SNAPSHOT option starts a consistent read for storage engines such as XtraDB and InnoDB that can do so, the same as if a START TRANSACTION followed by a SELECT from any InnoDB table was issued. MariaDB 5.3 introduced enhancements to this feature. See Enhancements for START TRANSACTION WITH CONSISTENT SNAPSHOT. Examples -------- START TRANSACTION; SELECT @A:=SUM(salary) FROM table1 WHERE type=1; UPDATE table2 SET summary=@A WHERE type=1; COMMIT; URL: https://mariadb.com/kb/en/start-transaction/https://mariadb.com/kb/en/start-transaction/ $%NAME_CONSTSyntax ------ NAME_CONST(name,value) Description ----------- Returns the given value. When used to produce a result set column, NAME_CONST() causes the column to have the given name. The arguments should be constants. This function is used internally when replicating stored procedures. It makes little sense to use it explicitly in SQL statements, and it was not supposed to be used like that. SELECT NAME_CONST('myname', 14); +--------+ | myname | +--------+ | 14 | +--------+ URL: https://mariadb.com/kb/en/name_const/https://mariadb.com/kb/en/name_const/a-  ! ؖ4o &%STOP SLAVESyntax ------ STOP SLAVE ["connection_name"] [thread_type [, thread_type] ... ] STOP ALL SLAVES [thread_type [, thread_type]] thread_type: IO_THREAD | SQL_THREAD Description ----------- Stops the slave threads. STOP SLAVE requires the SUPER privilege. Like START SLAVE, this statement may be used with the IO_THREAD and SQL_THREAD options to name the thread or threads to be stopped. In almost all cases, one never need to use the thread_type options. STOP SLAVE waits until any current replication event group affecting one or more non-transactional tables has finished executing (if there is any such replication group), or until the user issues a KILL QUERY or KILL CONNECTION statement. Note that STOP SLAVE doesn't delete the connection permanently. Next time you execute START SLAVE or the MariaDB server restarts, the slave connection is restored with it's original arguments. If you want to delete a connection, you should execute RESET SLAVE. STOP ALL SLAVES STOP ALL SLAVES stops all your running slaves. It will give you a note for every stopped connection. You can check the notes with SHOW WARNINGS. connection_name The connection_name option was added as part of multi-source replication added in MariaDB 10.0 If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the STOP SLAVE statement will apply to the specified master. connection_name is case-insensitive. URL: https://mariadb.com/kb/en/stop-slave/https://mariadb.com/kb/en/stop-slave/p/Transaction TimeoutsMariaDB has always had the wait_timeout and interactive_timeout settings, which close connections after a certain period of inactivity. However, these are by default set to a long wait period. In situations where transactions may be started, but not committed or rolled back, more granular control and a shorter timeout may be desirable so as to avoid locks being held for too long. MariaDB 10.3 introduced three new variables to handle this situation. idle_transaction_timeout (all transactions) idle_write_transaction_timeout (write transactions - called idle_readwrite_transaction_timeout until MariaDB 10.3.2) idle_readonly_transaction_timeout (read transactions) These accept a time in seconds to time out, by closing the connection, transactions that are idle for longer than this period. By default all are set to zero, or no timeout. idle_transaction_timeout affects all transactions, idle_write_transaction_timeout affects write transactions only and idle_readonly_transaction_timeout affects read transactions only. The latter two variables work independently. However, if either is set along with idle_transaction_timeout, the settings for idle_write_transaction_timeout or idle_readonly_transaction_timeout will take precedence. Examples -------- SET SESSION idle_transaction_timeout=2; BEGIN; SELECT * FROM t; Empty set (0.000 sec) ## wait 3 seconds SELECT * FROM t; ERROR 2006 (HY000): MySQL server has gone away SET SESSION idle_write_transaction_timeout=2; BEGIN; SELECT * FROM t; Empty set (0.000 sec) ## wait 3 seconds SELECT * FROM t; Empty set (0.000 sec) INSERT INTO t VALUES(1); ## wait 3 seconds SELECT * FROM t; ERROR 2006 (HY000): MySQL server has gone away SET SESSION idle_transaction_timeout=2, SESSION idle_readonly_transaction_timeout=10; BEGIN; SELECT * FROM t; Empty set (0.000 sec) ## wait 3 seconds SELECT * FROM t; Empty set (0.000 sec) ## wait 11 seconds SELECT * FROM t; ERROR 2006 (HY000): MySQL server has gone away URL: https://mariadb.com/kb/en/transaction-timeouts/https://mariadb.com/kb/en/transaction-timeouts/r*WAIT and NOWAITMariaDB 10.3.0 introduced extended syntax so that it is possible to set innodb_lock_wait_timeout and lock_wait_timeout for the following statements: Syntax ------ ALTER TABLE tbl_name [WAIT n|NOWAIT] ... CREATE ... INDEX ON tbl_name (index_col_name, ...) [WAIT n|NOWAIT] ... DROP INDEX ... [WAIT n|NOWAIT] DROP TABLE tbl_name [WAIT n|NOWAIT] ... LOCK TABLE ... [WAIT n|NOWAIT] OPTIMIZE TABLE tbl_name [WAIT n|NOWAIT] RENAME TABLE tbl_name [WAIT n|NOWAIT] ... SELECT ... FOR UPDATE [WAIT n|NOWAIT] SELECT ... LOCK IN SHARE MODE [WAIT n|NOWAIT] TRUNCATE TABLE tbl_name [WAIT n|NOWAIT] Description ----------- The lock wait timeout can be explicitly set in the statement by using either WAIT n (to set the wait in seconds) or NOWAIT, in which case the statement will immediately fail if the lock cannot be obtained. WAIT 0 is equivalent to NOWAIT. URL: https://mariadb.com/kb/en/wait-and-nowait/https://mariadb.com/kb/en/wait-and-nowait/tJ* Account LockingAccount locking was introduced in MariaDB 10.4.2. Description ----------- Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected). User accounts can be locked at creation, with the CREATE USER statement, or modified after creation with the ALTER USER statement. For example: CREATE USER 'lorin'@'localhost' ACCOUNT LOCK; or ALTER USER 'marijn'@'localhost' ACCOUNT LOCK; The server will return an ER_ACCOUNT_HAS_BEEN_LOCKED error when locked users attempt to connect: mysql -ulorin ERROR 4151 (HY000): Access denied, this account is locked The ALTER USER statement is also used to unlock a user: ALTER USER 'lorin'@'localhost' ACCOUNT UNLOCK; The SHOW CREATE USER statement will show whether the account is locked: SHOW CREATE USER 'marijn'@'localhost'; +-----------------------------------------------+ | CREATE USER for marijn@localhost | +-----------------------------------------------+ | CREATE USER 'marijn'@'localhost' ACCOUNT LOCK | +-----------------------------------------------+ as well as querying the mysql.global_priv table: SELECT CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) FROM mysql.global_priv WHERE user='marijn'; +--------------------------------------------------------------------------------------+ | CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) | +--------------------------------------------------------------------------------------+ | marijn@localhost => { "access": 0, "plugin": "mysql_native_password", "authentication_string": "", "account_locked": true, "password_last_changed": 1558017158 } | +--------------------------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/account-locking/https://mariadb.com/kb/en/account-locking/ SLEEPSyntax ------ SLEEP(duration) Description ----------- Sleeps (pauses) for the number of seconds given by the duration argument, then returns 0. If SLEEP() is interrupted, it returns 1. The duration may have a fractional part given in microseconds. Statements using the SLEEP() function are not safe for replication. Example SELECT SLEEP(5.5); +------------+ | SLEEP(5.5) | +------------+ | 0 | +------------+ 1 row in set (5.50 sec) URL: https://mariadb.com/kb/en/sleep/https://mariadb.com/kb/en/sleep/ %UUID_SHORTSyntax ------ UUID_SHORT() Description ----------- Returns a "short" universal identifier as a 64-bit unsigned integer (rather than a string-form 128-bit identifier as returned by the UUID() function). The value of UUID_SHORT() is guaranteed to be unique if the following conditions hold: The server_id of the current host is unique among your set of master and slave servers server_id is between 0 and 255 You don't set back your system time for your server between mysqld restarts You do not invoke UUID_SHORT() on average more than 16 million times per second between mysqld restarts The UUID_SHORT() return value is constructed this way: (server_id & 255) URL: https://mariadb.com/kb/en/uuid_short/https://mariadb.com/kb/en/uuid_short/X 3%of c~UOverview The MariaDB XA implementation is based on the X/Open CAE document Distributed Transaction Processing: The XA Specification. This document is published by The Open Group and available at http://www.opengroup.org/public/pubs/catalog/c193.htm. XA transactions are designed to allow distributed transactions, where a transaction manager (the application) controls a transaction which involves multiple resources. Such resources are usually DBMSs, but could be resources of any type. The whole set of required transactional operations is called a global transaction. Each subset of operations which involve a single resource is called a local transaction. XA used a 2-phases commit (2PC). With the first commit, the transaction manager tells each resource to prepare an effective commit, and waits for a confirm message. The changes are not still made effective at this point. If any of the resources encountered an error, the transaction manager will rollback the global transaction. If all resources communicate that the first commit is successful, the transaction manager can require a second commit, which makes the changes effective. In MariaDB, XA transactions can only be used with storage engines that support them. At least InnoDB, TokuDB, SPIDER and MyRocks support them. For InnoDB, XA transactions can be disabled by setting the innodb_support_xa server system variable to 0. Like regular transactions, XA transactions create metadata locks on accessed tables. XA transactions require REPEATABLE READ as a minimum isolation level. However, distributed transactions should always use SERIALIZABLE. Trying to start more than one XA transaction at the same time produces a 1400 error (SQLSTATE 'XAE09'). The same error is produced when attempting to start an XA transaction while a regular transaction is in effect. Trying to start a regular transaction while an XA transaction is in effect produces a 1399 error (SQLSTATE 'XAE07'). The statements that cause an implicit COMMIT for regular transactions produce a 1400 error (SQLSTATE 'XAE09') if a XA transaction is in effect. Internal XA vs External XA XA transactions are an overloaded term in MariaDB. If a storage engine is XA-capable, it can mean one or both of these: It supports MariaDB's internal two-phase commit API. This is transparent to the user. Sometimes this is called "internal XA", since MariaDB's internal transaction coordinator log can handle coordinating these transactions. It supports XA transactions, with the XA START, XA PREPARE, XA COMMIT, etc. statements. Sometimes this is called "external XA", since it requires the use of an external transaction coordinator to use this feature properly. Transaction Coordinator Log If you have two or more XA-capable storage engines enabled, then a transaction coordinator log must be available. There are currently two implementations of the transaction coordinator log: Binary log-based transaction coordinator log Memory-mapped file-based transaction coordinator log If the binary log is enabled on a server, then the server will use the binary log-based transaction coordinator log. Otherwise, it will use the memory-mapped file-based transaction coordinator log. See Transaction Coordinator Log for more information. Syntax ------ XA {START|BEGIN} xid [JOIN|RESUME] XA END xid [SUSPEND [FOR MIGRATE]] XA PREPARE xid XA COMMIT xid [ONE PHASE] XA ROLLBACK xid XA RECOVER [FORMAT=['RAW'|'SQL']] xid: gtrid [, bqual [, formatID ]] The interface to XA transactions is a set of SQL statements starting with XA. Each statement changes a transaction's state, determining which actions it can perform. A transaction which does not exist is in the NON-EXISTING state. XA START (or BEGIN) starts a transaction and defines its xid (a transaction identifier). The JOIN or RESUME keywords have no effect. The new transaction will be in ACTIVE state. The xid can have 3 components, though only the first one is mandatory. gtrid is a quoted string representing a global transaction identifier. bqual is a quoted string representing a local transaction identifier. formatID is an unsigned integer indicating the format used for the first two components; if not specified, defaults to 1. MariaDB does not interpret in any way these components, and only uses them to identify a transaction. xids of transactions in effect must be unique. XA END declares that the specified ACTIVE transaction is finished and it changes its state to IDLE. SUSPEND [FOR MIGRATE] has no effect. XA PREPARE prepares an IDLE transaction for commit, changing its state to PREPARED. This is the first commit. XA COMMIT definitely commits and terminates a transaction which has already been PREPARED. If the ONE PHASE clause is specified, this statements performs a 1-phase commit on an IDLE transaction. XA ROLLBACK rolls back and terminates an IDLE or PREPARED transaction. XA RECOVER shows information about all PREPARED transactions. When trying to execute an operation which is not allowed for the transaction's current state, an error is produced: XA COMMIT 'test' ONE PHASE; ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be executed when global transaction is in the ACTIVE state XA COMMIT 'test2'; ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be executed when global transaction is in the NON-EXISTING state XA RECOVER The XA RECOVER statement shows information about all transactions which are in the PREPARED state. It does not matter which connection created the transaction: if it has been PREPARED, it appears. But this does not mean that a connection can commit or rollback a transaction which was started by another connection. Note that transactions using a 1-phase commit are never in the PREPARED state, so they cannot be shown by XA RECOVER. XA RECOVER produces four columns: XA RECOVER; +----------+--------------+--------------+------+ | formatID | gtrid_length | bqual_length | data | +----------+--------------+--------------+------+ | 1 | 4 | 0 | test | +----------+--------------+--------------+------+ You can use XA RECOVER FORMAT='SQL' to get the data in a human readable form that can be directly copy-pasted into XA COMMIT or XA ROLLBACK. This is particularly useful for binary xid generated by some transaction coordinators. formatID is the formatID part of xid. data are the gtrid and bqual parts of xid, concatenated. gtrid_length and bqual_length are the lengths of gtrid and bqual, respectevely. Examples -------- 2-phases commit: XA START 'test'; INSERT INTO t VALUES (1,2); XA END 'test'; XA PREPARE 'test'; XA COMMIT 'test'; 1-phase commit: XA START 'test'; INSERT INTO t VALUES (1,2); XA END 'test'; XA COMMIT 'test' ONE PHASE; Human-readable: xa start '12\r34\t67\v78', 'abc\ndef', 3; insert t1 values (40); xa end '12\r34\t67\v78', 'abc\ndef', 3; xa prepare '12\r34\t67\v78', 'abc\ndef', 3; xa recover format='RAW'; +----------+--------------+--------------+--------------------+ | formatID | gtrid_length | bqual_length | data | +----------+--------------+--------------+--------------------+ 34 67v78abc 11 | 7 | 12 def | +----------+--------------+--------------+--------------------+ xa recover format='SQL'; +----------+--------------+--------------+-----------------------------------------------+ | formatID | gtrid_length | bqual_length | data | +----------+--------------+--------------+-----------------------------------------------+ | 3 | 11 | 7 | X'31320d3334093637763738',X'6162630a646566',3 | +----------+--------------+--------------+-----------------------------------------------+ xa rollback X'31320d3334093637763738',X'6162630a646566',3; Known Issues MariaDB Galera Cluster MariaDB Galera Cluster does not support XA transactions. See MDEV-10532 for more information on that. The request to implement that feature is being tracked at MDEV-17099. However, MariaDB Galera Cluster builds include a built-in plugin called wsrep. Prior to MariaDB 10.4.3, this plugin was internally considered an XA-capable storage engine. Consequently, these MariaDB Galera Cluster builds have mu"MariaDB 10.4 introduces a number of changes to the authentication process, intended to make things easier and more intuitive. Overview There are four main changes relating to authentication: It is possible to use more than one authentication plugin for each user account. For example, this can be useful to slowly migrate users to the more secure ed25519 authentication plugin over time, while allowing the old mysql_native_password authentication plugin as an alternative for the transitional period. The root@localhost user account created by mysql_install_db is created with the ability to use two authentication plugins. First, it is configured to try to use the unix_socket authentication plugin. This allows the the root@localhost user to login without a password via the local Unix socket file defined by the socket system variable, as long as the login is attempted from a process owned by the operating system root user account. Second, if authentication fails with the unix_socket authentication plugin, then it is configured to try to use the mysql_native_password authentication plugin. However, an invalid password is initially set, so in order to authenticate this way, a password must be set with SET PASSWORD. However, just using the unix_socket authentication plugin may be fine for many users, and it is very secure. You may want to try going without password authentication to see how well it works for you. Remember, the best way to keep your password safe is not to have one! All user accounts, passwords, and global privileges are now stored in the mysql.global_priv table. The mysql.user table still exists and has exactly the same set of columns as before, but it’s now a view that references the mysql.global_priv table. Tools that analyze the mysql.user table should continue to workas before. MariaDB 10.4 supports User Password Expiry, which is not active by default. Description ----------- As a result of the above changes, the open-for-everyone all-powerful root account is finally gone. And installation scripts will no longer demand that you “PLEASE REMEMBER TO SET A PASSWORD FOR THE MariaDB root USER !”, because the root account is securely created automatically. Two all-powerful accounts are created by default — root and the OS user that owns the data directory, typically mysql. They are created as: CREATE USER root@localhost IDENTIFIED VIA unix_socket OR mysql_native_password USING 'invalid' CREATE USER mysql@localhost IDENTIFIED VIA unix_socket OR mysql_native_password USING 'invalid' Using unix_socket means that if you are the system root user, you can login as root@locahost without a password. This technique was pioneered by Otto Kekäläinen in Debian MariaDB packages and has been successfully used in Debian since as early as MariaDB 10.0. It is based on a simple fact that asking the system root for a password adds no extra security — root has full access to all the data files and all process memory anyway. But not asking for a password means, there is no root password to forget (no need for the numerous tutorials on “how to reset MariaDB root password”). And if you want to script some tedious database work, there is no need to store the root password in plain text for the scipt to use (no need for debian-sys-maint user). Still, some users may wish to log in as MariaDB root without using sudo. Hence the old authentication method — conventional MariaDB password — is still available. By default it is disabled (“invalid” is not a valid password hash), but one can set the password with a usual SET PASSWORD statement. And still retain the password-less access via sudo. If you install MariaDB locally (say from a tarball, you would not want to use sudo to be able to login. This is why MariaDB creates a second all-powerful user with the same name as a system user that owns the data directory. In local (not system-wide) installations, this will be the user who installed MariaDB — they automatically get convenient password-less root-like access, because they can access all the data files anyway. Even if MariaDB is installed system-wide, you may not want to run your database maintenance scripts as system root — now you can run them as system mysql user. And you will know that they will never destroy your entire system, even if you make a typo in a shell script. However, seasoned MariaDB DBAs who are used to the old ways do need to makes some changes. See the examples below for common tasks. Cookbook After installing MariaDB system-wide the first thing you’ve got used to doing is logging in into the unprotected root account and protecting it, that is, setting the root password: $ sudo dnf install MariaDB-server $ mysql -uroot ... MariaDB> set password = password("XH4VmT3_jt"); This is not only unnecessary now, it will simply not work — there is no unprotected root account. To login as root use $ sudo dnf install MariaDB-server $ sudo mysql Note that it implies you are connecting via the unix socket, not tcp. If you happen to have protocol=tcp in a system-wide /etc/my.cnf file, use sudo mysql --protocol=socket. After installing MariaDB locally you’ve also used to connect to the unprotected root account using mysql -uroot. This will not work either, simply use mysql without specifying a username. If you've forgotten your root password, no problem — you can still connect using sudo and change the password. And if you've also removed unix_socket authentication, to restore access do as follows: restart MariaDB with --skip-grant-tables login into the unprotected server run FLUSH PRIVILEGES (note, before 10.4 this would’ve been the last step, not anymore). This disables --skip-grant-tables and allows you to change the stored authentication method. run SET PASSWORD FOR root@localhost to change the root password To view inside privilege tables, the old mysql.user table still exists. You can select from it as before, although you cannot update it anymore. It doesn’t show alternative authentication plugins and this was one of the reasons for switching to the mysql.global_priv table — complex authentication rules did not fit into rigid structure of a relational table. You can select from the new table, for example: select concat(user, '@', host, ' => ', json_detailed(priv)) from mysql.global_priv; Reverting to the Previous Authentication Method for root@localhost If you don't want the root@localhost user account created by mysql_install_db to use unix_socket authentication by default, then there are a few ways to revert to the previous mysql_native_password authentication method for this user account. Configuring mysql_install_db to Revert to the Previous Authentication Method One way to revert to the previous mysql_native_password authentication method for the root@localhost user account is to execute mysql_install_db with a special option. If mysql_install_db is executed while --auth-root-authentication-method=normal is specified, then it will create the default user accounts using the default behavior of MariaDB 10.3 and before. This means that the root@localhost user account will use mysql_native_password authentication by default. There are some other differences as well. See mysql_install_db: User Accounts Created by Default for more information. For example, the option can be set on the command-line while running mysql_install_db: mysql_install_db --user=mysql --datadir=/var/lib/mysql --auth-root-authentication-method=normal The option can also be set in an option file in an option group supported by mysql_install_db. For example: [mysql_install_db] auth_root_authentication_method=normal If the option is set in an option file and if mysql_install_db is executed, then mysql_install_db will read this option from the option file, and it will automatically set this option. Altering the User Account to Revert to the Previous Authentication Method If you have already installed MariaDB, and if the root@localhost user account is already using unix_socket authentication, then you can revert to the old mysql_native_password authenticatio<Syntax ------ CREATE [OR REPLACE] USER [IF NOT EXISTS] user_specification [,user_specification ...] [REQUIRE {NONE | tls_option [[AND] tls_option ...] }] [WITH resource_option [resource_option ...] ] [password_option | lock_option] user_specification: username [authentication_option] authentication_option: IDENTIFIED BY 'password' | IDENTIFIED BY PASSWORD 'password_hash' | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule ...] authentication_rule: authentication_plugin | authentication_plugin {USING|AS} 'authentication_string' | authentication_plugin {USING|AS} PASSWORD('password') tls_option: SSL | X509 | CIPHER 'cipher' | ISSUER 'issuer' | SUBJECT 'subject' resource_option: MAX_QUERIES_PER_HOUR count | MAX_UPDATES_PER_HOUR count | MAX_CONNECTIONS_PER_HOUR count | MAX_USER_CONNECTIONS count | MAX_STATEMENT_TIME time password_option: PASSWORD EXPIRE | PASSWORD EXPIRE DEFAULT | PASSWORD EXPIRE NEVER | PASSWORD EXPIRE INTERVAL N DAY lock_option: ACCOUNT LOCK | ACCOUNT UNLOCK } Description ----------- The CREATE USER statement creates new MariaDB accounts. To use it, you must have the global CREATE USER privilege or the INSERT privilege for the mysql database. For each account, CREATE USER creates a new row in the mysql.user table that has no privileges. If any of the specified accounts, or any permissions for the specified accounts, already exist, then the server returns ERROR 1396 (HY000). If an error occurs, CREATE USER will still create the accounts that do not result in an error. Only one error is produced for all users which have not been created: ERROR 1396 (HY000): Operation CREATE USER failed for 'u1'@'%','u2'@'%' CREATE USER, DROP USER, CREATE ROLE, and DROP ROLE all produce the same error code when they fail. See Account Names below for details on how account names are specified. OR REPLACE If the optional OR REPLACE clause is used, it is basically a shortcut for: DROP USER IF EXISTS name; CREATE USER name ...; For example: CREATE USER foo2@test IDENTIFIED BY 'password'; ERROR 1396 (HY000): Operation CREATE USER failed for 'foo2'@'test' CREATE OR REPLACE USER foo2@test IDENTIFIED BY 'password'; Query OK, 0 rows affected (0.00 sec) IF NOT EXISTS When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified user already exists. For example: CREATE USER foo2@test IDENTIFIED BY 'password'; ERROR 1396 (HY000): Operation CREATE USER failed for 'foo2'@'test' CREATE USER IF NOT EXISTS foo2@test IDENTIFIED BY 'password'; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+----------------------------------------------------+ | Level | Code | Message | +-------+------+----------------------------------------------------+ | Note | 1973 | Can't create user 'foo2'@'test'; it already exists | +-------+------+----------------------------------------------------+ 1 row in set (0.00 sec Authentication Options IDENTIFIED BY 'password' The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table. For example, if our password is mariadb, then we can create the user with: CREATE USER foo2@test IDENTIFIED BY 'mariadb'; If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set. The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password. IDENTIFIED BY PASSWORD 'password_hash' The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored to the mysql.user table as-is. For example, if our password is mariadb, then we can find the hash with: SELECT PASSWORD('mariadb'); +-------------------------------------------+ | PASSWORD('mariadb') | +-------------------------------------------+ | *54958E764CE10E50764C2EECBB71D01F08549980 | +-------------------------------------------+ 1 row in set (0.00 sec) And then we can create a user with the hash: CREATE USER foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980'; If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set. The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password. IDENTIFIED {VIA|WITH} authentication_plugin The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME. For example, this could be used with the PAM authentication plugin: CREATE USER foo2@test IDENTIFIED VIA pam; Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name: CREATE USER foo2@test IDENTIFIED VIA pam USING 'mariadb'; The exact meaning of the additional argument would depend on the specific authentication plugin. The USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this: CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret'); One can specify many authentication plugins, they all works as alternatives ways of authenticating a user: CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret') OR unix_socket; TLS Options By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them. To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors. See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support. You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available: Option | Description | REQUIRE NONE | TLS is not required for this account, but can still be used. | REQUIRE SSL | The account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options. | REQUIRE X509 | The account must use TLS andtXW must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options. | REQUIRE ISSUER 'issuer' | The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order. | REQUIRE SUBJECT 'subject' | The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order. | REQUIRE CIPHER 'cipher' | The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use one of the methods specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order. | The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required. For example, you can create a user account that requires these TLS options with the following: CREATE USER 'alice'@'%' REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland' AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com' AND CIPHER 'TLSv1.2'; If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS. See Securing Connections for Client and Server for information on how to enable TLS on the client and server. Resource Limit Options MariaDB 10.2.0 introduced a number of resource limit options. It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account: Limit Type | Decription | MAX_QUERIES_PER_HOUR | Number of statements that the account can issue per hour (including updates) | MAX_UPDATES_PER_HOUR | Number of updates (not queries) that the account can issue per hour | MAX_CONNECTIONS_PER_HOUR | Number of connections that the account can start per hour | MAX_USER_CONNECTIONS | Number of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections. | MAX_STATEMENT_TIME | Timeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute. | If any of these limits are set to 0, then there is no limit for that resource for that user. Here is an example showing how to create a user with resource limits: CREATE USER 'someone'@'localhost' WITH MAX_USER_CONNECTIONS 10 MAX_QUERIES_PER_HOUR 200; The resources are tracked per account, which means 'user'@'server'; not per user name or per connection. The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload. Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS). Account Names Account names have both a user name component and a host name component, and are specified as 'user_name'@'host_name'. The user name and host name may be unquoted, quoted as strings using double quotes (") or single quotes ('), or quoted as identifiers using backticks (`). You must use quotes when using special characters (such as a hyphen) or wildcard characters. If you quote, you must quote the user name and host name separately (for example 'user_name'@'host_name'). Host Name Component If the host name is not provided, it is assumed to be '%'. Host names may contain the wildcard characters % and _. They are matched as if by the LIKE clause. If you need to use a wildcard character literally (for example, to match a domain name with an underscore), prefix the character with a backslash. See LIKE for more information on escaping wildcard characters. Host name matches are case-insensitive. Host names can match either domain names or IP addresses. Use 'localhost' as the host name to allow only local client connections. You can use a netmask to match a range of IP addresses using 'base_ip/netmask' as the host name. A user with an IP address ip_addr will be allowed to connect if the following condition is true: ip_addr & netmask = base_ip You can only use netmasks that specify a multiple of 8 bits of the address to match. That is, only the following netmasks are allowed: 255.0.0.0 255.255.0.0 255.255.255.0 255.255.255.255 Using 255.255.255.255 is equivalent to not using a netmask at all. User Name Component User names must match exactly, including case. A user name that is empty is known as an anonymous account and is allowed to match a login attempt with any user name component. These are described more in the next section. For valid identifiers to use as user names, see Identifier Names. It is possible for more than one account to match when a user connects. MariaDB selects the first matching account after sorting according to the following criteria: Accounts with an exact host name are sorted before accounts using a wildcard in the host name. Host names using a netmask are considered to be exact for sorting. Accounts with a wildcard in the host name are sorted according to the position of the first wildcard character. Those with a wildcard character later in the host name sort before those with a wildcard character earlier in the host name. Accounts with a non-empty user name sort before accounts with an empty user name. Accounts with an empty user name are sorted last. As mentioned previously, these are known as anonymous accounts. These are described more in the next section. The following table shows a list of example account as sorted by these criteria: +---------+-------------+ | User | Host | +---------+-------------+ | joffrey | 192.168.0.3 | | | 192.168.0.% | | joffrey | 192.168.% | | | 192.168.% | +---------+-------------+ Once connected, you only have the privileges granted to the account that matched, not all accounts that could have matched. For example, consider the following commands: CREATE USER 'joffrey'@'192.168.0.3'; CREATE USER 'joffrey'@'%'; GRANT SELECT ON test.t1 to 'joffrey'@'192.168.0.3'; GRANT SELECT ON test.t2 to 'joffrey'@'%'; If you connect as joffrey from 192.168.0.3, you will have the SELECT privilege on the table test.t1, but not on the table test.t2. If you connect as joffrey from any other IP address, you will have the SELECT privilege on the table test.t2, but not on the table test.t1. Beginning with MariaDB 5.5.31, usernames can be up to 80 characters long. From MariaDB 10.0 the system tables are all by default this length. However, in order to enable this feature in MariaDB 5.5, the following schema changes must be made: ALTER TABLE mysql.user MODIFY User CHAR(80) BINARY NOT NULL DEFAULT ''; ALTER TABLE mysql.db MODIFY User CHAR(80) BINARY NOT NULL DEFAULT ''; ALTER TABLE mysql.tables_priv MODIFY User CHAR(80) BINARY NOT NULL DEFAULT ''; ALTER TABLE mysql.columns_priv MODIFY User CHAR(80) BINARY NOT NULL DEFAULT ''; ALTER TABLE mysql.procs_priv MODIFY User CHAR(80) BINARY NOT NULL DEFAULT ''; ALTER TABLE mysql.proc MODIFY definer CHAR(141) COLLATE utf8_bin NOT NULL DEFAULT ''; ALTER TABLE mysql.event MODIFY definer CHAR(141) COLLATE utf8_bin NOT NULL DEFAULT ''; ALTER TABLE mysql.proxies_priv MODIFY User CHAR(80) COLLATE utf8_bin NOT NULL DEFAULT ''; ALTER TABLE mysql.proxies_priv MODIFY Proxied_user CHAR(80) COLLATE utf8_bin NOT NULL DEFAULT ''; ALTER TABLE mysql.proxies_priv MODIFY Grantor CHAR(141) COLLATE utf8_bin NOT NULL DEFAULT ''; ALTER TABLE mysql.servers MODIFY Username CHAR(80) NOT NULL DEFAULT ''|The ALTER USER statement was introduced in MariaDB 10.2.0. Syntax ------ ALTER USER [IF EXISTS] user_specification [,user_specification] ... [REQUIRE {NONE | tls_option [[AND] tls_option] ...}] [WITH resource_option [resource_option] ...] [password_option | lock_option] user_specification: username [authentication_option] authentication_option: IDENTIFIED BY 'password' | IDENTIFIED BY PASSWORD 'password_hash' | IDENTIFIED {VIA|WITH} authentication_plugin | IDENTIFIED {VIA|WITH} authentication_plugin {USING|AS} 'authentication_string' | IDENTIFIED {VIA|WITH} authentication_plugin {USING|AS} PASSWORD('password') tls_option SSL | X509 | CIPHER 'cipher' | ISSUER 'issuer' | SUBJECT 'subject' resource_option MAX_QUERIES_PER_HOUR count | MAX_UPDATES_PER_HOUR count | MAX_CONNECTIONS_PER_HOUR count | MAX_USER_CONNECTIONS count | MAX_STATEMENT_TIME time password_option: PASSWORD EXPIRE | PASSWORD EXPIRE DEFAULT | PASSWORD EXPIRE NEVER | PASSWORD EXPIRE INTERVAL N DAY lock_option: ACCOUNT LOCK | ACCOUNT UNLOCK } Description ----------- The ALTER USER statement modifies existing MariaDB accounts. To use it, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. The global SUPER privilege is also required if the read_only system variable is enabled. If any of the specified user accounts do not yet exist, an error results. If an error occurs, ALTER USER will still modify the accounts that do not result in an error. Only one error is produced for all users which have not been modified. IF EXISTS When the IF EXISTS clause is used, MariaDB will return a warning instead of an error for each specified user that does not exist. Account Names For ALTER USER statements, account names are specified as the username argument in the same way as they are for CREATE USER statements. See account names from the CREATE USER page for details on how account names are specified. CURRENT_USER or CURRENT_USER() can also be used to alter the account logged into the current session. For example, to change the current user's password to mariadb: ALTER USER CURRENT_USER() IDENTIFIED BY 'mariadb'; Authentication Options IDENTIFIED BY 'password' The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table. For example, if our password is mariadb, then we can set the account's password with: ALTER USER foo2@test IDENTIFIED BY 'mariadb'; If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set. The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password. IDENTIFIED BY PASSWORD 'password_hash' The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored to the mysql.user table as-is. For example, if our password is mariadb, then we can find the hash with: SELECT PASSWORD('mariadb'); +-------------------------------------------+ | PASSWORD('mariadb') | +-------------------------------------------+ | *54958E764CE10E50764C2EECBB71D01F08549980 | +-------------------------------------------+ 1 row in set (0.00 sec) And then we can set an account's password with the hash: ALTER USER foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980'; If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set. The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password. IDENTIFIED {VIA|WITH} authentication_plugin The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME. For example, this could be used with the PAM authentication plugin: ALTER USER foo2@test IDENTIFIED VIA pam; Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name: ALTER USER foo2@test IDENTIFIED VIA pam USING 'mariadb'; The exact meaning of the additional argument would depend on the specific authentication plugin. In MariaDB 10.4 and later, the USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this: ALTER USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret'); TLS Options By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them. To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors. See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support. You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available: Option | Description | REQUIRE NONE | TLS is not required for this account, but can still be used. | REQUIRE SSL | The account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options. | REQUIRE X509 | The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options. | REQUIRE ISSUER 'issuer' | The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order. | REQUIRE SUBJECT 'subject' | The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order. | REQUIRE CIPHER 'cipher' | The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use one of the methods specified in the string cipher. This option implies REQUIRE SSL. This option can be combiKa ined with the ISSUER, and SUBJECT options in any order. | The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required. For example, you can alter a user account to require these TLS options with the following: ALTER USER 'alice'@'%' REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland' AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com' AND CIPHER 'TLSv1.2'; If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS. See Securing Connections for Client and Server for information on how to enable TLS on the client and server. Resource Limit Options MariaDB 10.2.0 introduced a number of resource limit options. It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account: Limit Type | Decription | MAX_QUERIES_PER_HOUR | Number of statements that the account can issue per hour (including updates) | MAX_UPDATES_PER_HOUR | Number of updates (not queries) that the account can issue per hour | MAX_CONNECTIONS_PER_HOUR | Number of connections that the account can start per hour | MAX_USER_CONNECTIONS | Number of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections. | MAX_STATEMENT_TIME | Timeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute. | If any of these limits are set to 0, then there is no limit for that resource for that user. Here is an example showing how to set an account's resource limits: ALTER USER 'someone'@'localhost' WITH MAX_USER_CONNECTIONS 10 MAX_QUERIES_PER_HOUR 200; The resources are tracked per account, which means 'user'@'server'; not per user name or per connection. The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload. Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS). Password Expiry Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global setting, for example: ALTER USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY; ALTER USER 'monty'@'localhost' PASSWORD EXPIRE NEVER; ALTER USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT; See User Password Expiry for more details. Account Locking Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected). For example: ALTER USER 'marijn'@'localhost' ACCOUNT LOCK; See Account Locking for more details. URL: https://mariadb.com/kb/en/alter-user/https://mariadb.com/kb/en/flush/https://mariadb.com/kb/en/show-status/https://mariadb.com/kb/en/explain/https://mariadb.com/kb/en/alter-table/https://mariadb.com/kb/en/create-function/https://mariadb.com/kb/en/create-procedure/https://mariadb.com/kb/en/create-table/https://mariadb.com/kb/en/create-view/AL); INSERT INTO table2 (a) VALUES (1); SELECT * FROM table2; +------+------------+ | a | b | +------+------------+ | 1 | 0000000002 | +------+------------+ 1 row in set (0.00 sec) You can also use virtual columns to implement a "poor man's partial index". See example at the end of Unique Index. URL: https://mariadb.com/kb/en/generated-columns/d & ' +e *? & " & Egx ~$ DROP USERSyntax ------ DROP USER [IF EXISTS] user_name [, user_name] ... Description ----------- The DROP USER statement removes one or more MariaDB accounts. It removes privilege rows for the account from all grant tables. To use this statement, you must have the global CREATE USER privilege or the DELETE privilege for the mysql database. Each account is named using the same format as for the CREATE USER statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For additional information about specifying account names, see CREATE USER. Note that, if you specify an account that is currently connected, it will not be deleted until the connection is closed. The connection will not be automatically closed. If any of the specified user accounts do not exist, ERROR 1396 (HY000) results. If an error occurs, DROP USER will still drop the accounts that do not result in an error. Only one error is produced for all users which have not been dropped: ERROR 1396 (HY000): Operation DROP USER failed for 'u1'@'%','u2'@'%' Failed CREATE or DROP operations, for both users and roles, produce the same error code. IF EXISTS The IF EXISTS clause was added in MariaDB 10.1.3 If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the user does not exist. Examples -------- DROP USER bob; IF EXISTS: DROP USER bob; ERROR 1396 (HY000): Operation DROP USER failed for 'bob'@'%' DROP USER IF EXISTS bob; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+---------------------------------------------+ | Level | Code | Message | +-------+------+---------------------------------------------+ | Note | 1974 | Can't drop user 'bob'@'%'; it doesn't exist | +-------+------+---------------------------------------------+ URL: https://mariadb.com/kb/en/drop-user/https://mariadb.com/kb/en/drop-user/zH / User Password ExpiryUser password expiry was introduced in MariaDB 10.4.3. Password expiry permits administrators to expire user passwords, either manually or automatically. System Variables There are two system variables which affect password expiry: default_password_lifetime, which determines the amount of time between requiring the user to change their password. 0, the default, means automatic password expiry is not active. The second variable, disconnect_on_expired_password determines whether a client is permitted to connect if their password has expired, or whether they are permitted to connect in sandbox mode, able to perform a limited subset of queries related to resetting the password, in particular SET PASSWORD and SET. Setting a Password Expiry Limit for a User Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global using the CREATE USER or ALTER USER statements, for example: CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY; ALTER USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY; Limits can be disabled by use of the NEVER keyword, for example: CREATE USER 'monty'@'localhost' PASSWORD EXPIRE NEVER; ALTER USER 'monty'@'localhost' PASSWORD EXPIRE NEVER; A manually set limit can be restored the system default by use of DEFAULT, for example: CREATE USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT; ALTER USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT; SHOW CREATE USER The SHOW CREATE USER statement will display information about the password expiry status of the user. Unlike MySQL, it will not display if the user is unlocked, or if the password expiry is set to default. CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY; CREATE USER 'konstantin'@'localhost' PASSWORD EXPIRE NEVER; CREATE USER 'amse'@'localhost' PASSWORD EXPIRE DEFAULT; SHOW CREATE USER 'monty'@'localhost'; +------------------------------------------------------------------+ | CREATE USER for monty@localhost | +------------------------------------------------------------------+ | CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY | +------------------------------------------------------------------+ SHOW CREATE USER 'konstantin'@'localhost'; +------------------------------------------------------------+ | CREATE USER for konstantin@localhost | +------------------------------------------------------------+ | CREATE USER 'konstantin'@'localhost' PASSWORD EXPIRE NEVER | +------------------------------------------------------------+ SHOW CREATE USER 'amse'@'localhost'; +--------------------------------+ | CREATE USER for amse@localhost | +--------------------------------+ | CREATE USER 'amse'@'localhost' | +--------------------------------+ --connect-expired-password Client Option The mysql client --connect-expired-password option notifies the server that the client is prepared to handle expired password sandbox mode (even if the --batch option was specified). URL: https://mariadb.com/kb/en/user-password-expiry/https://mariadb.com/kb/en/user-password-expiry/!Syntax ------ NOT, ! Description ----------- Logical NOT. Evaluates to 1 if the operand is 0, to 0 if the operand is non-zero, and NOT NULL returns NULL. By default, the ! operator has a higher precedence. If the HIGH_NOT_PRECEDENCE SQL_MODE flag is set, NOT and ! have the same precedence. Examples -------- SELECT NOT 10; +--------+ | NOT 10 | +--------+ | 0 | +--------+ SELECT NOT 0; +-------+ | NOT 0 | +-------+ | 1 | +-------+ SELECT NOT NULL; +----------+ | NOT NULL | +----------+ | NULL | +----------+ SELECT ! (1+1); +---------+ | ! (1+1) | +---------+ | 0 | +---------+ SELECT ! 1+1; +-------+ | ! 1+1 | +-------+ | 1 | +-------+ URL: https://mariadb.com/kb/en/not/https://mariadb.com/kb/en/not/ &&Syntax ------ AND, && Description ----------- Logical AND. Evaluates to 1 if all operands are non-zero and not NULL, to 0 if one or more operands are 0, otherwise NULL is returned. For this operator, short-circuit evaluation can be used. Examples -------- SELECT 1 && 1; +--------+ | 1 && 1 | +--------+ | 1 | +--------+ SELECT 1 && 0; +--------+ | 1 && 0 | +--------+ | 0 | +--------+ SELECT 1 && NULL; +-----------+ | 1 && NULL | +-----------+ | NULL | +-----------+ SELECT 0 && NULL; +-----------+ | 0 && NULL | +-----------+ | 0 | +-----------+ SELECT NULL && 0; +-----------+ | NULL && 0 | +-----------+ | 0 | +-----------+ URL: https://mariadb.com/kb/en/and/https://mariadb.com/kb/en/and/XORSyntax ------ XOR Description ----------- XOR stands for eXclusive OR. Returns NULL if either operand is NULL. For non-NULL operands, evaluates to 1 if an odd number of operands is non-zero, otherwise 0 is returned. Examples -------- SELECT 1 XOR 1; +---------+ | 1 XOR 1 | +---------+ | 0 | +---------+ SELECT 1 XOR 0; +---------+ | 1 XOR 0 | +---------+ | 1 | +---------+ SELECT 1 XOR NULL; +------------+ | 1 XOR NULL | +------------+ | NULL | +------------+ In the following example, the right 1 XOR 1 is evaluated first, and returns 0. Then, 1 XOR 0 is evaluated, and 1 is returned. SELECT 1 XOR 1 XOR 1; +---------------+ | 1 XOR 1 XOR 1 | +---------------+ | 1 | +---------------+ URL: https://mariadb.com/kb/en/xor/https://mariadb.com/kb/en/xor/V+[^ ;[Syntax ------ GRANT priv_type [(column_list)] [, priv_type [(column_list)]] ... ON [object_type] priv_level TO user_specification [ user_options ...] user_specification: username [authentication_option] authentication_option: IDENTIFIED BY 'password' | IDENTIFIED BY PASSWORD 'password_hash' | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule ...] authentication_rule: authentication_plugin | authentication_plugin {USING|AS} 'authentication_string' | authentication_plugin {USING|AS} PASSWORD('password') GRANT PROXY ON username TO username [, username] ... [WITH GRANT OPTION] user_options: [REQUIRE {NONE | tls_option [[AND] tls_option] ...}] [WITH with_option [with_option] ...] object_type: TABLE | FUNCTION | PROCEDURE priv_level: * | *.* | db_name.* | db_name.tbl_name | tbl_name | db_name.routine_name with_option: GRANT OPTION | resource_option resource_option: MAX_QUERIES_PER_HOUR count | MAX_UPDATES_PER_HOUR count | MAX_CONNECTIONS_PER_HOUR count | MAX_USER_CONNECTIONS count | MAX_STATEMENT_TIME time tls_option: SSL | X509 | CIPHER 'cipher' | ISSUER 'issuer' | SUBJECT 'subject' Description ----------- The GRANT statement allows you to grant privileges or roles to accounts. To use GRANT, you must have the GRANT OPTION privilege, and you must have the privileges that you are granting. Use the REVOKE statement to revoke privileges granted with the GRANT statement. Use the SHOW GRANTS statement to determine what privileges an account has. Account Names For GRANT statements, account names are specified as the username argument in the same way as they are for CREATE USER statements. See account names from the CREATE USER page for details on how account names are specified. Implicit Account Creation The GRANT statement also allows you to implicitly create accounts in some cases. If the account does not yet exist, then GRANT can implicitly create it. To implicitly create an account with GRANT, a user is required to have the same privileges that would be required to explicitly create the account with the CREATE USER statement. If the NO_AUTO_CREATE_USER SQL_MODE is set, then accounts can only be created if authentication information is specified, or with a CREATE USER statement. If no authentication information is provided, GRANT will produce an error when the specified account does not exist, for example: show variables like '%sql_mode%' ; +---------------+--------------------------------------------+ | Variable_name | Value | +---------------+--------------------------------------------+ | sql_mode | NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +---------------+--------------------------------------------+ GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED BY ''; ERROR 1133 (28000): Can't find any matching row in the user table GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED VIA PAM using 'mariadb' require ssl ; Query OK, 0 rows affected (0.00 sec) select host, user from mysql.user where user='user123' ; +------+----------+ | host | user | +------+----------+ | % | user123 | +------+----------+ Privilege Levels Privileges can be set globally, for an entire database, for a table or routine, or for individual columns in a table. Certain privileges can only be set at certain levels. Global privileges are granted using *.* for priv_level. Global privileges include privileges to administer the database and manage user accounts, as well as privileges for all tables, functions, and procedures. Global privileges are stored in the mysql.user table. Database privileges are granted using db_name.* for priv_level, or using just * to use default database. Database privileges include privileges to create tables and functions, as well as privileges for all tables, functions, and procedures in the database. Database privileges are stored in the mysql.db table. Table privileges are granted using db_name.tbl_name for priv_level, or using just tbl_name to specify a table in the default database. The TABLE keyword is optional. Table privileges include the ability to select and change data in the table. Certain table privileges can be granted for individual columns. Column privileges are granted by specifying a table for priv_level and providing a column list after the privilege type. They allow you to control exactly which columns in a table users can select and change. Function privileges are granted using FUNCTION db_name.routine_name for priv_level, or using just FUNCTION routine_name to specify a function in the default database. Procedure privileges are granted using PROCEDURE db_name.routine_name for priv_level, or using just PROCEDURE routine_name to specify a procedure in the default database. The USAGE Privilege The USAGE privilege grants no real privileges. The SHOW GRANTS statement will show a global USAGE privilege for a newly-created user. You can use USAGE with the GRANT statement to change options like GRANT OPTION and MAX_USER_CONNECTIONS without changing any account privileges. The ALL PRIVILEGES Privilege The ALL PRIVILEGES privilege grants all available privileges. Granting all privileges only affects the given privilege level. For example, granting all privileges on a table does not grant any privileges on the database or globally. Using ALL PRIVILEGES does not grant the special GRANT OPTION privilege. You can use ALL instead of ALL PRIVILEGES. The GRANT OPTION Privilege Use the WITH GRANT OPTION clause to give users the ability to grant privileges to other users at the given privilege level. Users with the GRANT OPTION privilege can only grant privileges they have. They cannot grant privileges at a higher privilege level than they have the GRANT OPTION privilege. The GRANT OPTION privilege cannot be set for individual columns. If you use WITH GRANT OPTION when specifying column privileges, the GRANT OPTION privilege will be granted for the entire table. Using the WITH GRANT OPTION clause is equivalent to listing GRANT OPTION as a privilege. Global Privileges The following table lists the privileges that can be granted globally. You can also grant all database, table, and function privileges globally. When granted globally, these privileges apply to all databases, tables, or functions, including those created later. To set a global privilege, use *.* for priv_level. Privilege | Description | CREATE USER | Create a user using the CREATE USER statement, or implicitly create a user with the GRANT statement. | FILE | Read and write files on the server, using statements like LOAD DATA INFILE or functions like LOAD_FILE(). Also needed to create CONNECT outward tables. MariaDB server must have the permissions to access those files. | GRANT OPTION | Grant global privileges. You can only grant privileges that you have. | PROCESS | Show information about the active processes, via SHOW PROCESSLIST or mysqladmin processlist. | RELOAD | Execute FLUSH statements or equivalent mysqladmin commands. | REPLICATION CLIENT | Execute SHOW MASTER STATUS and SHOW SLAVE STATUS informative statements. | REPLICATION SLAVE | Accounts used by slave servers on the master need this privilege. This is needed to get the updates made on the master. | SHOW DATABASES | List all databases using the SHOW DATABASES statement. Without the SHOW DATABASES privilege, you can still issue the SHOW DATABASES statement, but it will only list databases containing tables on which you have privileges. | SHUTDOWN | Shut down the server using SHUTDOWN or the mysqladmin shutdown command. | SUPER | Execute superuser statements: CHANGE MASTER TO, KILL (users who do not have this privilege can only KILL their own threads), PURGE LOGS, SET global system variables, or the mysqladmin debug command. Also, this permission allows the user to write data even if the read_only startup option is set, enable or disable logging, enable or disable replication on slaves, specify a DEFINER for statements that support that clause, connect once after reaching the MAX_CONNECTIONS. If a statement has been specified for the init-connect mysqld optrMion, that command will not be executed when a user with SUPER privileges connects to the server. | Database Privileges The following table lists the privileges that can be granted at the database level. You can also grant all table and function privileges at the database level. Table and function privileges on a database apply to all tables or functions in that database, including those created later. To set a privilege for a database, specify the database using db_name.* for priv_level, or just use * to specify the default database. Privilege | Description | CREATE | Create a database using the CREATE DATABASE statement, when the privilege is granted for a database. You can grant the CREATE privilege on databases that do not yet exist. This also grants the CREATE privilege on all tables in the database. | CREATE ROUTINE | Create Stored Programs using the CREATE PROCEDURE and CREATE FUNCTION statements. | CREATE TEMPORARY TABLES | Create temporary tables with the CREATE TEMPORARY TABLE statement. This privilege enable writing and dropping those temporary tables | DROP | Drop a database using the DROP DATABASE statement, when the privilege is granted for a database. This also grants the DROP privilege on all tables in the database. | EVENT | Create, drop and alter EVENTs. Added in MySQL 5.1.6. | GRANT OPTION | Grant database privileges. You can only grant privileges that you have. | LOCK TABLES | Acquire explicit locks using the LOCK TABLES statement; you also need to have the SELECT privilege on a table, in order to lock it. | Table Privileges Privilege | Description | ALTER | Change the structure of an existing table using the ALTER TABLE statement. | CREATE | Create a table using the CREATE TABLE statement. You can grant the CREATE privilege on tables that do not yet exist. | CREATE VIEW | Create a view using the CREATE_VIEW statement. | DELETE | Remove rows from a table using the DELETE statement. | DELETE HISTORY | Remove historical rows from a table using the DELETE HISTORY statement. Displays as DELETE VERSIONING ROWS when running SHOW GRANTS until MariaDB 10.3.15 and until MariaDB 10.4.5 (MDEV-17655), or when running SHOW PRIVILEGES (MDEV-20382). From MariaDB 10.3.4. From MariaDB 10.3.5, if a user has the SUPER privilege but not this privilege, running mysql_upgrade will grant this privilege as well. | DROP | Drop a table using the DROP TABLE statement or a view using the DROP VIEW statement. Also required to execute the TRUNCATE TABLE statement. | GRANT OPTION | Grant table privileges. You can only grant privileges that you have. | INDEX | Create an index on a table using the CREATE INDEX statement. Without the INDEX privilege, you can still create indexes when creating a table using the CREATE TABLE statement if the you have the CREATE privilege, and you can create indexes using the ALTER TABLE statement if you have the ALTER privilege. | INSERT | Add rows to a table using the INSERT statement. The INSERT privilege can also be set on individual columns; see Column Privileges below for details. | REFERENCES | Unused. | SELECT | Read data from a table using the SELECT statement. The SELECT privilege can also be set on individual columns; see Column Privileges below for details. | SHOW VIEW | Show the CREATE VIEW statement to create a view using the SHOW CREATE VIEW statement. | TRIGGER | Execute triggers associated to tables you update, execute the CREATE TRIGGER and DROP TRIGGER statements. You will still be able to see triggers. | UPDATE | Update existing rows in a table using the UPDATE statement. UPDATE statements usually include a WHERE clause to update only certain rows. You must have SELECT privileges on the table or the appropriate columns for the WHERE clause. The UPDATE privilege can also be set on individual columns; see Column Privileges below for details. | Column Privileges Some table privileges can be set for individual columns of a table. To use column privileges, specify the table explicitly and provide a list of column names after the privilege type. For example, the following statement would allow the user to read the names and positions of employees, but not other information from the same table, such as salaries. GRANT SELECT (name, position) on Employee to 'jeffrey'@'localhost'; Privilege | Description | INSERT (column_list) | Add rows specifying values in columns using the INSERT statement. If you only have column-level INSERT privileges, you must specify the columns you are setting in the INSERT statement. All other columns will be set to their default values, or NULL. | REFERENCES (column_list) | Unused. | SELECT (column_list) | Read values in columns using the SELECT statement. You cannot access or query any columns for which you do not have SELECT privileges, including in WHERE, ON, GROUP BY, and ORDER BY clauses. | UPDATE (column_list) | Update values in columns of existing rows using the UPDATE statement. UPDATE statements usually include a WHERE clause to update only certain rows. You must have SELECT privileges on the table or the appropriate columns for the WHERE clause. | Function Privileges Privilege | Description | ALTER ROUTINE | Change the characteristics of a stored function using the ALTER FUNCTION statement. | EXECUTE | Use a stored function. You need SELECT privileges for any tables or columns accessed by the function. | GRANT OPTION | Grant function privileges. You can only grant privileges that you have. | Procedure Privileges Privilege | Description | ALTER ROUTINE | Change the characteristics of a stored procedure using the ALTER PROCEDURE statement. | EXECUTE | Execute a stored procedure using the CALL statement. The privilege to call a procedure may allow you to perform actions you wouldn't otherwise be able to do, such as insert rows into a table. | GRANT OPTION | Grant procedure privileges. You can only grant privileges that you have. | Proxy Privileges Privilege | Description | PROXY | Permits one user to be a proxy for another. | The PROXY privilege allows one user to proxy as another user, which means their privileges change to that of the proxy user, and the CURRENT_USER() function returns the user name of the proxy user. The PROXY privilege only works with authentication plugins that support it. The default mysql_native_password authentication plugin does not support proxy users. The pam authentication plugin is the only plugin included with MariaDB that currently supports proxy users. The PROXY privilege is commonly used with the pam authentication plugin to enable user and group mapping with PAM. For example, to grant the PROXY privilege to an anonymous account that authenticates with the pam authentication plugin, you could execute the following: CREATE USER 'dba'@'%' IDENTIFIED BY 'strongpassword'; GRANT ALL PRIVILEGES ON *.* TO 'dba'@'%' ; CREATE USER ''@'%' IDENTIFIED VIA pam USING 'mariadb'; GRANT PROXY ON 'dba'@'%' TO ''@'%'; A user account can only grant the PROXY privilege for a specific user account if the granter also has the PROXY privilege for that specific user account, and if that privilege is defined WITH GRANT OPTION. For example, the following example fails because the granter does not have the PROXY privilege for that specific user account at all: SELECT USER(), CURRENT_USER(); +-----------------+-----------------+ | USER() | CURRENT_USER() | +-----------------+-----------------+ | alice@localhost | alice@localhost | +-----------------+-----------------+ SHOW GRANTS; +-----------------------------------------------------------------------------------------------------------------------+ | Grants for alice@localhost | +-----------------------------------------------------------------------------------------------------------------------+ | GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' | +-----------------------------------------------------------------------------------------------------------------------+ GRANT PROXY٢[ ON 'dba'@'localhost' TO 'bob'@'localhost'; ERROR 1698 (28000): Access denied for user 'alice'@'localhost' And the following example fails because the granter does have the PROXY privilege for that specific user account, but it is not defined WITH GRANT OPTION: SELECT USER(), CURRENT_USER(); +-----------------+-----------------+ | USER() | CURRENT_USER() | +-----------------+-----------------+ | alice@localhost | alice@localhost | +-----------------+-----------------+ SHOW GRANTS; +-----------------------------------------------------------------------------------------------------------------------+ | Grants for alice@localhost | +-----------------------------------------------------------------------------------------------------------------------+ | GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' | | GRANT PROXY ON 'dba'@'localhost' TO 'alice'@'localhost' | +-----------------------------------------------------------------------------------------------------------------------+ MariaDB [(none)]> GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost'; ERROR 1698 (28000): Access denied for user 'alice'@'localhost' But the following example succeeds because the granter does have the PROXY privilege for that specific user account, and it is defined WITH GRANT OPTION: SELECT USER(), CURRENT_USER(); +-----------------+-----------------+ | USER() | CURRENT_USER() | +-----------------+-----------------+ | alice@localhost | alice@localhost | +-----------------+-----------------+ SHOW GRANTS; +-----------------------------------------------------------------------------------------------------------------------------------------+ | Grants for alice@localhost | +-----------------------------------------------------------------------------------------------------------------------------------------+ | GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT OPTION | | GRANT PROXY ON 'dba'@'localhost' TO 'alice'@'localhost' WITH GRANT OPTION | +-----------------------------------------------------------------------------------------------------------------------------------------+ GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost'; Query OK, 0 rows affected (0.004 sec) A user account can grant the PROXY privilege for any other user account if the granter has the PROXY privilege for the ''@'%' anonymous user account, like this: GRANT PROXY ON ''@'%' TO 'dba'@'localhost' WITH GRANT OPTION; For example, the following example succeeds because the user can grant the PROXY privilege for any other user account: SELECT USER(), CURRENT_USER(); +-----------------+-----------------+ | USER() | CURRENT_USER() | +-----------------+-----------------+ | alice@localhost | alice@localhost | +-----------------+-----------------+ SHOW GRANTS; +-----------------------------------------------------------------------------------------------------------------------------------------+ | Grants for alice@localhost | +-----------------------------------------------------------------------------------------------------------------------------------------+ | GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT OPTION | | GRANT PROXY ON ''@'%' TO 'alice'@'localhost' WITH GRANT OPTION | +-----------------------------------------------------------------------------------------------------------------------------------------+ GRANT PROXY ON 'app1_dba'@'localhost' TO 'bob'@'localhost'; Query OK, 0 rows affected (0.004 sec) GRANT PROXY ON 'app2_dba'@'localhost' TO 'carol'@'localhost'; Query OK, 0 rows affected (0.004 sec) The default root user accounts created by mysql_install_db have this privilege. For example: GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION; GRANT PROXY ON ''@'%' TO 'root'@'localhost' WITH GRANT OPTION; This allows the default root user accounts to grant the PROXY privilege for any other user account, and it also allows the default root user accounts to grant others the privilege to do the same. Authentication Options The authentication options for the GRANT statement are the same as those for the CREATE USER statement. IDENTIFIED BY 'password' The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table. For example, if our password is mariadb, then we can create the user with: GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY 'mariadb'; If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set. If the user account already exists and if you provide the IDENTIFIED BY clause, then the user's password will be changed. You must have the privileges needed for the SET PASSWORD statement to change a user's password with GRANT. The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password. IDENTIFIED BY PASSWORD 'password_hash' The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored to the mysql.user table as-is. For example, if our password is mariadb, then we can find the hash with: SELECT PASSWORD('mariadb'); +-------------------------------------------+ | PASSWORD('mariadb') | +-------------------------------------------+ | *54958E764CE10E50764C2EECBB71D01F08549980 | +-------------------------------------------+ 1 row in set (0.00 sec) And then we can create a user with the hash: GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980'; If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set. If the user account already exists and if you provide the IDENTIFIED BY clause, then the user's password will be changed. You must have the privileges needed for the SET PASSWORD statement to change a user's password with GRANT. The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password. IDENTIFIED {VIA|WITH} authentication_plugin The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME. For example, this could be used with the PAM authentication plugin: GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam; Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name: GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam USING 'mariadb'; The exact meaning of the additional argument would depend on the specific authentication plugin. The USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this: CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret'); One can specify many authentication plugins, they all works as alternatives ways of authenticating a user: CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret') OR unix_socket; Resource Limit OptioOJns MariaDB 10.2.0 introduced a number of resource limit options. It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account: Limit Type | Decription | MAX_QUERIES_PER_HOUR | Number of statements that the account can issue per hour (including updates) | MAX_UPDATES_PER_HOUR | Number of updates (not queries) that the account can issue per hour | MAX_CONNECTIONS_PER_HOUR | Number of connections that the account can start per hour | MAX_USER_CONNECTIONS | Number of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections. | MAX_STATEMENT_TIME | Timeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute. | If any of these limits are set to 0, then there is no limit for that resource for that user. To set resource limits for an account, if you do not want to change that account's privileges, you can issue a GRANT statement with the USAGE privilege, which has no meaning. The statement can name some or all limit types, in any order. Here is an example showing how to set resource limits: GRANT USAGE ON *.* TO 'someone'@'localhost' WITH MAX_USER_CONNECTIONS 0 MAX_QUERIES_PER_HOUR 200; The resources are tracked per account, which means 'user'@'server'; not per user name or per connection. The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload. Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS). TLS Options By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them. To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors. See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support. You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available: Option | Description | REQUIRE NONE | TLS is not required for this account, but can still be used. | REQUIRE SSL | The account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options. | REQUIRE X509 | The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options. | REQUIRE ISSUER 'issuer' | The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order. | REQUIRE SUBJECT 'subject' | The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order. | REQUIRE CIPHER 'cipher' | The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use one of the methods specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order. | The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required. For example, you can create a user account that requires these TLS options with the following: GRANT USAGE ON *.* TO 'alice'@'%' REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland' AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com' AND CIPHER 'TLSv1.2'; If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS. See Securing Connections for Client and Server for information on how to enable TLS on the client and server. Roles Roles were introduced in MariaDB 10.0.5. Syntax ------ GRANT role TO grantee [, grantee2 ... ] [ WITH ADMIN OPTION ] The GRANT statement is also used to grant the use a role to one or more users or other roles. In order to be able to grant a role, the grantor doing so must have permission to do so (see WITH ADMIN in the CREATE ROLE article). Specifying the WITH ADMIN OPTION permits the grantee to in turn grant the role to another. For example, the following commands show how to grant the same role to a couple different users. GRANT journalist TO hulda; GRANT journalist TO berengar WITH ADMIN OPTION; If a user has been granted a role, they do not automatically obtain all permissions associated with that role. These permissions are only in use when the user activates the role with the SET ROLE statement. Grant Examples Granting Root-like Privileges You can create a user that has privileges similar to the default root accounts by executing the following: CREATE USER 'alexander'@'localhost'; GRANT ALL PRIVILEGES ON *.* to 'alexander'@'localhost' WITH GRANT OPTION; URL: https://mariadb.com/kb/en/grant/ھ&={ {& RENAME USERSyntax ------ RENAME USER old_user TO new_user [, old_user TO new_user] ... Description ----------- The RENAME USER statement renames existing MariaDB accounts. To use it, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. Each account is named using the same format as for the CREATE USER statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. If any of the old user accounts do not exist or any of the new user accounts already exist, ERROR 1396 (HY000) results. If an error occurs, RENAME USER will still rename the accounts that do not result in an error. Examples -------- CREATE USER 'donald', 'mickey'; RENAME USER 'donald' TO 'duck'@'localhost', 'mickey' TO 'mouse'@'localhost'; URL: https://mariadb.com/kb/en/rename-user/https://mariadb.com/kb/en/rename-user/|! REVOKEPrivileges Syntax ------ REVOKE priv_type [(column_list)] [, priv_type [(column_list)]] ... ON [object_type] priv_level FROM user [, user] ... REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ... Description ----------- The REVOKE statement enables system administrators to revoke privileges (or roles - see section below) from MariaDB accounts. Each account is named using the same format as for the GRANT statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For details on the levels at which privileges exist, the allowable priv_type and priv_level values, and the syntax for specifying users and passwords, see GRANT. To use the first REVOKE syntax, you must have the GRANT OPTION privilege, and you must have the privileges that you are revoking. To revoke all privileges, use the second syntax, which drops all global, database, table, column, and routine privileges for the named user or users: REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ... To use this REVOKE syntax, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. See GRANT. Examples -------- REVOKE SUPER ON *.* FROM 'alexander'@'localhost'; Roles Roles were introduced in MariaDB 10.0.5. Syntax ------ REVOKE role [, role ...] FROM grantee [, grantee2 ... ] Description ----------- REVOKE is also used to remove a role from a user or another role that it's previously been assigned to. If a role has previously been set as a default role, REVOKE does not remove the record of the default role from the mysql.user table. If the role is subsequently granted again, it will again be the user's default. Use SET DEFAULT ROLE NONE to explicitly remove this. Before MariaDB 10.1.13, the REVOKE role statement was not permitted in prepared statements. Example REVOKE journalist FROM hulda URL: https://mariadb.com/kb/en/revoke/https://mariadb.com/kb/en/revoke/ & CREATE ROLERoles were introduced in MariaDB 10.0.5. Syntax ------ CREATE [OR REPLACE] ROLE [IF NOT EXISTS] role [WITH ADMIN {CURRENT_USER | CURRENT_ROLE | user | role}] Description ----------- The CREATE ROLE statement creates one or more MariaDB roles. To use it, you must have the global CREATE USER privilege or the INSERT privilege for the mysql database. For each account, CREATE ROLE creates a new row in the mysql.user table that has no privileges, and with the corresponding is_role field set to Y. It also creates a record in the mysql.roles_mapping table. If any of the specified roles already exist, ERROR 1396 (HY000) results. If an error occurs, CREATE ROLE will still create the roles that do not result in an error. The maximum length for a role is 128 characters. Role names can be quoted, as explained in the Identifier names page. Only one error is produced for all roles which have not been created: ERROR 1396 (HY000): Operation CREATE ROLE failed for 'a','b','c' Failed CREATE or DROP operations, for both users and roles, produce the same error code. PUBLIC and NONE are reserved, and cannot be used as role names. Before MariaDB 10.1.13, the CREATE ROLE statement was not permitted in prepared statements. For valid identifiers to use as role names, see Identifier Names. WITH ADMIN The optional WITH ADMIN clause determines whether the current user, the current role or another user or role has use of the newly created role. If the clause is omitted, WITH ADMIN CURRENT_USER is treated as the default, which means that the current user will be able to GRANT this role to users. OR REPLACE The OR REPLACE clause was added in MariaDB 10.1.3 If the optional OR REPLACE clause is used, it acts as a shortcut for: DROP ROLE IF EXISTS name; CREATE ROLE name ...; IF NOT EXISTS The IF NOT EXISTS clause was added in MariaDB 10.1.3 When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified role already exists. Cannot be used together with the OR REPLACE clause. Examples -------- CREATE ROLE journalist; CREATE ROLE developer WITH ADMIN lorinda; The OR REPLACE and IF NOT EXISTS clauses: CREATE ROLE journalist; ERROR 1396 (HY000): Operation CREATE ROLE failed for 'journalist' CREATE OR REPLACE ROLE journalist; Query OK, 0 rows affected (0.00 sec) CREATE ROLE IF NOT EXISTS journalist; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+---------------------------------------------------+ | Level | Code | Message | +-------+------+---------------------------------------------------+ | Note | 1975 | Can't create role 'journalist'; it already exists | +-------+------+---------------------------------------------------+ URL: https://mariadb.com/kb/en/create-role/https://mariadb.com/kb/en/create-role/.Assignment Operator (:=)Syntax ------ var_name := expr Description ----------- Assignment operator for assigning a value. The value on the right is assigned to the variable on left. Unlike the = operator, := can always be used to assign a value to a variable. This operator works with both user-defined variables and local variables. When assigning the same value to several variables, LAST_VALUE() can be useful. Examples -------- SELECT @x := 10; +----------+ | @x := 10 | +----------+ | 10 | +----------+ SELECT @x, @y := @x; +------+----------+ | @x | @y := @x | +------+----------+ | 10 | 10 | +------+----------+ URL: https://mariadb.com/kb/en/assignment-operator/https://mariadb.com/kb/en/assignment-operator/ 'GROUP_CONCATSyntax ------ GROUP_CONCAT(expr) Description ----------- This function returns a string result with the concatenated non-NULL values from a group. It returns NULL if there are no non-NULL values. The maximum returned length in bytes is determined by the group_concat_max_len server system variable, which defaults to 1M (>= MariaDB 10.2.4) or 1K ( URL: https://mariadb.com/kb/en/group_concat/https://mariadb.com/kb/en/group_concat/ &STDDEV_SAMPSyntax ------ STDDEV_SAMP(expr) Description ----------- Returns the sample standard deviation of expr (the square root of VAR_SAMP()). It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, STDDEV_SAMP() can be used as a window function. STDDEV_SAMP() returns NULL if there were no matching rows. URL: https://mariadb.com/kb/en/stddev_samp/https://mariadb.com/kb/en/stddev_samp/ ;  xuP} ' SET PASSWORDSyntax ------ SET PASSWORD [FOR user] = { PASSWORD('some password') | OLD_PASSWORD('some password') | 'encrypted password' } Description ----------- The SET PASSWORD statement assigns a password to an existing MariaDB user account. If the password is specified using the PASSWORD() or OLD_PASSWORD() function, the literal text of the password should be given. If the password is specified without using either function, the password should be the already-encrypted password value as returned by PASSWORD(). OLD_PASSWORD() should only be used if your MariaDB/MySQL clients are very old (< 4.0.0). With no FOR clause, this statement sets the password for the current user. Any client that has connected to the server using a non-anonymous account can change the password for that account. With a FOR clause, this statement sets the password for a specific account on the current server host. Only clients that have the UPDATE privilege for the mysql database can do this. The user value should be given in user_name@host_name format, where user_name and host_name are exactly as they are listed in the User and Host columns of the mysql.user table entry. The argument to PASSWORD() and the password given to MariaDB clients can be of arbitrary length. Authentication Plugin Support In MariaDB 10.4 and later, SET PASSWORD (with or without PASSWORD()) works for accounts authenticated via any authentication plugin that supports passwords stored in the mysql.global_priv table. The ed25519, mysql_native_password, and mysql_old_password authentication plugins store passwords in the mysql.global_priv table. If you run SET PASSWORD on an account that authenticates with one of these authentication plugins that stores passwords in the mysql.global_priv table, then the PASSWORD() function is evaluated by the specific authentication plugin used by the account. The authentication plugin hashes the password with a method that is compatible with that specific authentication plugin. The unix_socket, named_pipe, gssapi, and pam authentication plugins do not store passwords in the mysql.global_priv table. These authentication plugins rely on other methods to authenticate the user. If you attempt to run SET PASSWORD on an account that authenticates with one of these authentication plugins that doesn't store a password in the mysql.global_priv table, then MariaDB Server will raise a warning like the following: SET PASSWORD is ignored for users authenticating via unix_socket plugin See Authentication from MariaDB 10.4 for an overview of authentication changes in MariaDB 10.4. MariaDB until 10.3 In MariaDB 10.3 and before, SET PASSWORD (with or without PASSWORD()) only works for accounts authenticated via mysql_native_password or mysql_old_password authentication plugins Passwordless User Accounts User accounts do not always require passwords to login. The unix_socket , named_pipe and gssapi authentication plugins do not require a password to authenticate the user. The pam authentication plugin may or may not require a password to authenticate the user, depending on the specific configuration. The mysql_native_password and mysql_old_password authentication plugins require passwords for authentication, but the password can be blank. In that case, no password is required. If you provide a password while attempting to log into the server as an account that doesn't require a password, then MariaDB server will simply ignore the password. In MariaDB 10.4 and later, a user account can be defined to use multiple authentication plugins in a specific order of preference. This specific scenario may be more noticeable in these versions, since an account could be associated with some authentication plugins that require a password, and some that do not. Example For example, if you had an entry with User and Host column values of 'bob' and '%.loc.gov', you would write the statement like this: SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass'); URL: https://mariadb.com/kb/en/set-password/https://mariadb.com/kb/en/set-password/ $ DROP ROLERoles were introduced in MariaDB 10.0.5. Syntax ------ DROP ROLE [IF EXISTS] role_name [,role_name ...] Description ----------- The DROP ROLE statement removes one or more MariaDB roles. To use this statement, you must have the global CREATE USER privilege or the DELETE privilege for the mysql database. DROP ROLE does not disable roles for connections which selected them with SET ROLE. If a role has previously been set as a default role, DROP ROLE does not remove the record of the default role from the mysql.user table. If the role is subsequently recreated and granted, it will again be the user's default. Use SET DEFAULT ROLE NONE to explicitly remove this. If any of the specified user accounts do not exist, ERROR 1396 (HY000) results. If an error occurs, DROP ROLE will still drop the roles that do not result in an error. Only one error is produced for all roles which have not been dropped: ERROR 1396 (HY000): Operation DROP ROLE failed for 'a','b','c' Failed CREATE or DROP operations, for both users and roles, produce the same error code. Before MariaDB 10.1.13, the DROP ROLE statement was not permitted in prepared statements. IF EXISTS The IF EXISTS clause was added in MariaDB 10.1.3 If the IF EXISTS clause is used, MariaDB will return a warning instead of an error if the role does not exist. Examples -------- DROP ROLE journalist; The same thing using the optional IF EXISTS clause: DROP ROLE journalist; ERROR 1396 (HY000): Operation DROP ROLE failed for 'journalist' DROP ROLE IF EXISTS journalist; Query OK, 0 rows affected, 1 warning (0.00 sec) Note (Code 1975): Can't drop role 'journalist'; it doesn't exist URL: https://mariadb.com/kb/en/drop-role/https://mariadb.com/kb/en/drop-role/ $BENCHMARKSyntax ------ BENCHMARK(count,expr) Description ----------- The BENCHMARK() function executes the expression expr repeatedly count times. It may be used to time how quickly MariaDB processes the expression. The result value is always 0. The intended use is from within the mysql client, which reports query execution times. Examples -------- SELECT BENCHMARK(1000000,ENCODE('hello','goodbye')); +----------------------------------------------+ | BENCHMARK(1000000,ENCODE('hello','goodbye')) | +----------------------------------------------+ | 0 | +----------------------------------------------+ 1 row in set (0.21 sec) URL: https://mariadb.com/kb/en/benchmark/https://mariadb.com/kb/en/benchmark/^*BINLOG_GTID_POSFrom version 10.0.2, MariaDB supports global transaction IDs for replication. Syntax ------ BINLOG_GTID_POS(binlog_filename,binlog_offset) Description ----------- The BINLOG_GTID_POS() function takes as input an old-style binary log position in the form of a file name and a file offset. It looks up the position in the current binlog, and returns a string representation of the corresponding GTID position. If the position is not found in the current binlog, NULL is returned. Examples -------- SELECT BINLOG_GTID_POS("master-bin.000001", 600); URL: https://mariadb.com/kb/en/binlog_gtid_pos/https://mariadb.com/kb/en/binlog_gtid_pos/ $COLLATIONSyntax ------ COLLATION(str) Description ----------- Returns the collation of the string argument. If str is not a string, it is considered as a binary string (so the function returns 'binary'). This applies to NULL, too. The return value is a string in the utf8 character set. See Character Sets and Collations. Examples -------- SELECT COLLATION('abc'); +-------------------+ | COLLATION('abc') | +-------------------+ | latin1_swedish_ci | +-------------------+ SELECT COLLATION(_utf8'abc'); +-----------------------+ | COLLATION(_utf8'abc') | +-----------------------+ | utf8_general_ci | +-----------------------+ URL: https://mariadb.com/kb/en/collation/https://mariadb.com/kb/en/collation/+6 *~) Roles OverviewRoles were introduced in MariaDB 10.0.5. Description ----------- A role bundles a number of privileges together. It assists larger organizations where, typically, a number of users would have the same privileges, and, previously, the only way to change the privileges for a group of users was by changing each user's privileges individually. Alternatively, multiple external users could have been assigned the same user, and there would have been no way to see which actual user was responsible for which action. With roles, managing this is easy. For example, there could be a number of users assigned to a journalist role, with identical privileges. Changing the privileges for all the journalists is a matter of simply changing the role's privileges, while the individual user is still linked with any changes that take place. Roles are created with the CREATE ROLE statement, and dropped with the DROP ROLE statement. Roles are then assigned to a user with an extension to the GRANT statement, while privileges are assigned to a role in the regular way with GRANT. Similarly, the REVOKE statement can be used to both revoke a role from a user, or revoke a privilege from a role. Once a user has connected, he can obtain all privileges associated with a role by setting a role with the SET ROLE statement. The CURRENT_ROLE function returns the currently set role for the session, if any. Only roles granted directly to a user can be set, roles granted to other roles cannot. Instead the privileges granted to a role, which is, in turn, granted to another role (grantee), will be immediately available to any user who sets this second grantee role. Roles were implemented as a GSoC 2013 project by Vicentiu Ciorbaru. The SET DEFAULT ROLE statement allows one to set a default role for a user. A default role is automatically enabled when a user connects (an implicit SET ROLE statement is executed immediately after a connection is established). System Tables Information about roles and who they've been granted to can be found in the Information Schema APPLICABLE_ROLES table as well as the mysql.ROLES_MAPPING table. The Information Schema ENABLED_ROLES table shows the enabled roles for the current session. Examples -------- Creating a role and granting a privilege: CREATE ROLE journalist; GRANT SHOW DATABASES ON *.* TO journalist; GRANT journalist to hulda; Note, that hulda has no SHOW DATABASES privilege, even though she was granted the journalist role. She needs to set the role first: SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | +--------------------+ SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | NULL | +--------------+ SET ROLE journalist; SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | journalist | +--------------+ SHOW DATABASES; +--------------------+ | Database | +--------------------+ | ... | | information_schema | | mysql | | performance_schema | | test | | ... | +--------------------+ SET ROLE NONE; Roles can be granted to roles: CREATE ROLE writer; GRANT SELECT ON data.* TO writer; GRANT writer TO journalist; But one does not need to set a role granted to a role. For example, hulda will automatically get all writer privileges when she sets the journalist role: SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | NULL | +--------------+ SHOW TABLES FROM data; Empty set (0.01 sec) SET ROLE journalist; SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | journalist | +--------------+ SHOW TABLES FROM data; +------------------------------+ | Tables_in_data | +------------------------------+ | set1 | | ... | +------------------------------+ Roles and Views (and Stored Routines) When a user sets a role, he, in a sense, has two identities with two associated sets of privileges. But a view (or a stored routine) can have only one definer. So, when a view (or a stored routine) is created with the SQL SECURITY DEFINER, one can specify whether the definer should be CURRENT_USER (and the view will have none of the privileges of the user's role) or CURRENT_ROLE (in this case, the view will use role's privileges, but none of the user's privileges). As a result, sometimes one can create a view that is impossible to use. CREATE ROLE r1; GRANT ALL ON db1.* TO r1; GRANT r1 TO foo@localhost; GRANT ALL ON db.* TO foo@localhost; SELECT CURRENT_USER +---------------+ | current_user | +---------------+ | foo@localhost | +---------------+ SET ROLE r1; CREATE TABLE db1.t1 (i int); CREATE VIEW db.v1 AS SELECT * FROM db1.t1; SHOW CREATE VIEW db.v1; +------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+ | View | Create View | character_set_client | collation_connection | +------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+ | v1 | CREATE ALGORITHM=UNDEFINED DEFINER=`foo`@`localhost` SQL SECURITY DEFINER VIEW `db`.`v1` AS SELECT `db1`.`t1`.`i` AS `i` from `db1`.`t1` | utf8 | utf8_general_ci | +------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+ CREATE DEFINER=CURRENT_ROLE VIEW db.v2 AS SELECT * FROM db1.t1; SHOW CREATE VIEW db.b2; +------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+ | View | Create View | character_set_client | collation_connection | +------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+ | v2 | CREATE ALGORITHM=UNDEFINED DEFINER=`r1` SQL SECURITY DEFINER VIEW `db`.`v2` AS select `db1`.`t1`.`a` AS `a` from `db1`.`t1` | utf8 | utf8_general_ci | +------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+ Other Resources Roles Review by Peter Gulutzan URL: https://mariadb.com/kb/en/roles_overview/https://mariadb.com/kb/en/roles_overview/ S(CONNECTION_IDSyntax ------ CONNECTION_ID() Description ----------- Returns the connection ID (thread ID) for the connection. Every thread (including events) has an ID that is unique among the set of currently connected clients. Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits. Examples -------- SELECT CONNECTION_ID(); +-----------------+ | CONNECTION_ID() | +-----------------+ | 3 | +-----------------+ URL: https://mariadb.com/kb/en/connection_id/https://mariadb.com/kb/en/connection_id/!SCHEMASyntax ------ SCHEMA() Description ----------- This function is a synonym for DATABASE(). URL: https://mariadb.com/kb/en/schema/https://mariadb.com/kb/en/schema/u d[ e# SET ROLERoles were introduced in MariaDB 10.0.5. Syntax ------ SET ROLE { role | NONE } Description ----------- The SET ROLE statement enables a role, along with all of its associated permissions, for the current session. To unset a role, use NONE . If a role that doesn't exist, or to which the user has not been assigned, is specified, an ERROR 1959 (OP000): Invalid role specification error occurs. From MariaDB 10.1.1, an automatic SET ROLE is implicitly performed when a user connects if that user has been assigned a default role. See SET DEFAULT ROLE. Example SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | NULL | +--------------+ SET ROLE staff; SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | staff | +--------------+ SET ROLE NONE; Query OK, 0 rows affected (0.00 sec) SELECT CURRENT_ROLE(); +----------------+ | CURRENT_ROLE() | +----------------+ | NULL | +----------------+ URL: https://mariadb.com/kb/en/set-role/https://mariadb.com/kb/en/set-role/$+ SET DEFAULT ROLEDefault roles were implemented in MariaDB 10.1.1. Syntax ------ SET DEFAULT ROLE { role | NONE } [ FOR user@host ] Description ----------- The SET DEFAULT ROLE statement sets a default role for a specified (or current) user. A default role is automatically enabled when a user connects (an implicit SET ROLE statement is executed immediately after a connection is established). To be able to set a role as a default, one needs the privileges to enable this role (if you cannot do SET ROLE X, you won't be able to do SET DEFAULT ROLE X). To set a default role for another user one needs to have write access to the mysql database. To remove a user's default role, use SET DEFAULT ROLE NONE [ FOR user@host ]. The record of the default role is not removed if the role is dropped or revoked, so if the role is subsequently re-created or granted, it will again be the user's default role. The default role is stored in a new column in the mysql.user table, and currently viewing this table is the only way to see which role has been assigned to a user as the default. Examples -------- Setting a default role for the current user: SET DEFAULT ROLE journalist; Removing a default role from the current user: SET DEFAULT ROLE NONE; URL: https://mariadb.com/kb/en/set-default-role/https://mariadb.com/kb/en/set-default-role/ & AES_ENCRYPTSyntax ------ AES_ENCRYPT(str,key_str) Description ----------- AES_ENCRYPT() and AES_DECRYPT() allow encryption and decryption of data using the official AES (Advanced Encryption Standard) algorithm, previously known as "Rijndael." Encoding with a 128-bit key length is used, but you can extend it up to 256 bits by modifying the source. We chose 128 bits because it is much faster and it is secure enough for most purposes. AES_ENCRYPT() encrypts a string str using the key key_str, and returns a binary string. AES_DECRYPT() decrypts the encrypted string and returns the original string. The input arguments may be any length. If either argument is NULL, the result of this function is also NULL. Because AES is a block-level algorithm, padding is used to encode uneven length strings and so the result string length may be calculated using this formula: 16 x (trunc(string_length / 16) + 1) If AES_DECRYPT() detects invalid data or incorrect padding, it returns NULL. However, it is possible for AES_DECRYPT() to return a non-NULL value (possibly garbage) if the input data or the key is invalid. Examples -------- INSERT INTO t VALUES (AES_ENCRYPT('text',SHA2('password',512))); URL: https://mariadb.com/kb/en/aes_encrypt/https://mariadb.com/kb/en/aes_encrypt/# COMPRESSSyntax ------ COMPRESS(string_to_compress) Description ----------- Compresses a string and returns the result as a binary string. This function requires MariaDB to have been compiled with a compression library such as zlib. Otherwise, the return value is always NULL. The compressed string can be uncompressed with UNCOMPRESS(). The have_compress server system variable indicates whether a compression library is present. Examples -------- SELECT LENGTH(COMPRESS(REPEAT('a',1000))); +------------------------------------+ | LENGTH(COMPRESS(REPEAT('a',1000))) | +------------------------------------+ | 21 | +------------------------------------+ SELECT LENGTH(COMPRESS('')); +----------------------+ | LENGTH(COMPRESS('')) | +----------------------+ | 0 | +----------------------+ SELECT LENGTH(COMPRESS('a')); +-----------------------+ | LENGTH(COMPRESS('a')) | +-----------------------+ | 13 | +-----------------------+ SELECT LENGTH(COMPRESS(REPEAT('a',16))); +----------------------------------+ | LENGTH(COMPRESS(REPEAT('a',16))) | +----------------------------------+ | 15 | +----------------------------------+ URL: https://mariadb.com/kb/en/compress/https://mariadb.com/kb/en/compress/ 'SESSION_USERSyntax ------ SESSION_USER() Description ----------- SESSION_USER() is a synonym for USER(). URL: https://mariadb.com/kb/en/session_user/https://mariadb.com/kb/en/session_user/ &SYSTEM_USERSyntax ------ SYSTEM_USER() Description ----------- SYSTEM_USER() is a synonym for USER(). URL: https://mariadb.com/kb/en/system_user/https://mariadb.com/kb/en/system_user/:$<Syntax ------ URL: https://mariadb.com/kb/en/less-than/https://mariadb.com/kb/en/less-than/C-<=Syntax ------ URL: https://mariadb.com/kb/en/less-than-or-equal/https://mariadb.com/kb/en/less-than-or-equal/ &BETWEEN ANDSyntax ------ expr BETWEEN min AND max Description ----------- If expr is greater than or equal to min and expr is less than or equal to max, BETWEEN returns 1, otherwise it returns 0. This is equivalent to the expression (min URL: https://mariadb.com/kb/en/between-and/https://mariadb.com/kb/en/between-and/#GREATESTSyntax ------ GREATEST(value1,value2,...) Description ----------- With two or more arguments, returns the largest (maximum-valued) argument. The arguments are compared using the same rules as for LEAST(). Examples -------- SELECT GREATEST(2,0); +---------------+ | GREATEST(2,0) | +---------------+ | 2 | +---------------+ SELECT GREATEST(34.0,3.0,5.0,767.0); +------------------------------+ | GREATEST(34.0,3.0,5.0,767.0) | +------------------------------+ | 767.0 | +------------------------------+ SELECT GREATEST('B','A','C'); +-----------------------+ | GREATEST('B','A','C') | +-----------------------+ | C | +-----------------------+ URL: https://mariadb.com/kb/en/greatest/https://mariadb.com/kb/en/greatest/\#INTERVALSyntax ------ INTERVAL(N,N1,N2,N3,...) Description ----------- Returns the index of the last argument that is less than the first argument or is NULL. Returns 0 if N < N1, 1 if N < N2, 2 if N < N3 and so on or -1 if N is NULL. All arguments are treated as integers. It is required that N1 < N2 < N3 URL: https://mariadb.com/kb/en/interval/https://mariadb.com/kb/en/interval/ &IS NOT NULLSyntax ------ IS NOT NULL Description ----------- Tests whether a value is not NULL. See also NULL Values in MariaDB. Examples -------- SELECT 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL; +---------------+---------------+------------------+ | 1 IS NOT NULL | 0 IS NOT NULL | NULL IS NOT NULL | +---------------+---------------+------------------+ | 1 | 1 | 0 | +---------------+---------------+------------------+ URL: https://mariadb.com/kb/en/is-not-null/https://mariadb.com/kb/en/is-not-null/QiSvp .?m 3AI  ~& DES_DECRYPTSyntax ------ DES_DECRYPT(crypt_str[,key_str]) Description ----------- Decrypts a string encrypted with DES_ENCRYPT(). If an error occurs, this function returns NULL. This function works only if MariaDB has been configured with TLS support. If no key_str argument is given, DES_DECRYPT() examines the first byte of the encrypted string to determine the DES key number that was used to encrypt the original string, and then reads the key from the DES key file to decrypt the message. For this to work, the user must have the SUPER privilege. The key file can be specified with the --des-key-file server option. If you pass this function a key_str argument, that string is used as the key for decrypting the message. If the crypt_str argument does not appear to be an encrypted string, MariaDB returns the given crypt_str. URL: https://mariadb.com/kb/en/des_decrypt/https://mariadb.com/kb/en/des_decrypt/ r& DES_ENCRYPTSyntax ------ DES_ENCRYPT(str[,{key_num|key_str}]) Description ----------- Encrypts the string with the given key using the Triple-DES algorithm. This function works only if MariaDB has been configured with TLS support. The encryption key to use is chosen based on the second argument to DES_ENCRYPT(), if one was given. With no argument, the first key from the DES key file is used. With a key_num argument, the given key number (0-9) from the DES key file is used. With a key_str argument, the given key string is used to encrypt str. The key file can be specified with the --des-key-file server option. The return string is a binary string where the first character is CHAR(128 | key_num). If an error occurs, DES_ENCRYPT() returns NULL. The 128 is added to make it easier to recognize an encrypted key. If you use a string key, key_num is 127. The string length for the result is given by this formula: new_len = orig_len + (8 - (orig_len % 8)) + 1 Each line in the DES key file has the following format: key_num des_key_str Each key_num value must be a number in the range from 0 to 9. Lines in the file may be in any order. des_key_str is the string that is used to encrypt the message. There should be at least one space between the number and the key. The first key is the default key that is used if you do not specify any key argument to DES_ENCRYPT(). You can tell MariaDB to read new key values from the key file with the FLUSH DES_KEY_FILE statement. This requires the RELOAD privilege. One benefit of having a set of default keys is that it gives applications a way to check for the existence of encrypted column values, without giving the end user the right to decrypt those values. Examples -------- SELECT customer_address FROM customer_table WHERE crypted_credit_card = DES_ENCRYPT('credit_card_number'); URL: https://mariadb.com/kb/en/des_encrypt/https://mariadb.com/kb/en/des_encrypt/! ENCODESyntax ------ ENCODE(str,pass_str) Description ----------- ENCODE is not considered cryptographically secure, and should not be used for password encryption. Encrypt str using pass_str as the password. To decrypt the result, use DECODE(). The result is a binary string of the same length as str. The strength of the encryption is based on how good the random generator is. It is not recommended to rely on the encryption performed by the ENCODE function. Using a salt value (changed when a password is updated) will improve matters somewhat, but for storing passwords, consider a more cryptographically secure function, such as SHA2(). Examples -------- ENCODE('not so secret text', CONCAT('random_salt','password')) URL: https://mariadb.com/kb/en/encode/https://mariadb.com/kb/en/encode/" ENCRYPTSyntax ------ ENCRYPT(str[,salt]) Description ----------- Encrypts a string using the Unix crypt() system call, returning an encrypted binary string. The salt argument should be a string with at least two characters or the returned result will be NULL. If no salt argument is given, a random value of sufficient length is used. It is not recommended to use ENCRYPT() with utf16, utf32 or ucs2 multi-byte character sets because the crypt() system call expects a string terminated with a zero byte. Note that the underlying crypt() system call may have some limitations, such as ignoring all but the first eight characters. If the have_crypt system variable is set to NO (because the crypt() system call is not available), the ENCRYPT function will always return NULL. Examples -------- SELECT ENCRYPT('encrypt me'); +-----------------------+ | ENCRYPT('encrypt me') | +-----------------------+ | 4I5BsEx0lqTDk | +-----------------------+ URL: https://mariadb.com/kb/en/encrypt/https://mariadb.com/kb/en/encrypt/ C' OLD_PASSWORDSyntax ------ OLD_PASSWORD(str) Description ----------- OLD_PASSWORD() was added to MySQL when the implementation of PASSWORD() was changed to improve security. OLD_PASSWORD() returns the value of the old (pre-MySQL 4.1) implementation of PASSWORD() as a string, and is intended to permit you to reset passwords for any pre-4.1 clients that need to connect to a more recent MySQL server version, or any version of MariaDB, without locking them out. As of MariaDB 5.5, the return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string. The return value is 16 bytes in length, or NULL if the argument was NULL. URL: https://mariadb.com/kb/en/old_password/https://mariadb.com/kb/en/old_password/!ISNULLSyntax ------ ISNULL(expr) Description ----------- If expr is NULL, ISNULL() returns 1, otherwise it returns 0. See also NULL Values in MariaDB. Examples -------- SELECT ISNULL(1+1); +-------------+ | ISNULL(1+1) | +-------------+ | 0 | +-------------+ SELECT ISNULL(1/0); +-------------+ | ISNULL(1/0) | +-------------+ | 1 | +-------------+ URL: https://mariadb.com/kb/en/isnull/https://mariadb.com/kb/en/isnull/.Operator PrecedenceThe precedence is the order in which the SQL operators are evaluated. The following list shows the SQL operator precedence. Operators that appear first in the list have a higher precedence. Operators which are listed together have the same precedence. INTERVAL BINARY, COLLATE ! - (unary minus), [[bitwise-not|]] (unary bit inversion) || (string concatenation) ^ *, /, DIV, %, MOD -, + & | = (comparison), , >=, >, URL: https://mariadb.com/kb/en/operator-precedence/https://mariadb.com/kb/en/operator-precedence/&&Syntax ------ & Description ----------- Bitwise AND. Converts the values to binary and compares bits. Only if both the corresponding bits are 1 is the resulting bit also 1. See also bitwise OR. Examples -------- SELECT 2&1; +-----+ | 2&1 | +-----+ | 0 | +-----+ SELECT 3&1; +-----+ | 3&1 | +-----+ | 1 | +-----+ SELECT 29 & 15; +---------+ | 29 & 15 | +---------+ | 13 | +---------+ URL: https://mariadb.com/kb/en/bitwise_and/https://mariadb.com/kb/en/bitwise_and/B%<<Syntax ------ value1 URL: https://mariadb.com/kb/en/shift-left/https://mariadb.com/kb/en/shift-left/f}d='n&z J 6 v= SHA1Syntax ------ SHA1(str), SHA(str) Description ----------- Calculates an SHA-1 160-bit checksum for the string str, as described in RFC 3174 (Secure Hash Algorithm). The value is returned as a string of 40 hex digits, or NULL if the argument was NULL. As of MariaDB 5.5, the return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string. Examples -------- SELECT SHA1('some boring text'); +------------------------------------------+ | SHA1('some boring text') | +------------------------------------------+ | af969fc2085b1bb6d31e517d5c456def5cdd7093 | +------------------------------------------+ URL: https://mariadb.com/kb/en/sha1/https://mariadb.com/kb/en/sha1/ SHA2SHA2() was introduced in MariaDB 5.5 Syntax ------ SHA2(str,hash_len) Description ----------- Given a string str, calculates an SHA-2 checksum, which is considered more cryptographically secure than its SHA-1 equivalent. The SHA-2 family includes SHA-224, SHA-256, SHA-384, and SHA-512, and the hash_len must correspond to one of these, i.e. 224, 256, 384 or 512. 0 is equivalent to 256. The return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. NULL is returned if the hash length is not valid, or the string str is NULL. SHA2 will only work if MariaDB was has been configured with TLS support. Examples -------- SELECT SHA2('Maria',224); +----------------------------------------------------------+ | SHA2('Maria',224) | +----------------------------------------------------------+ | 6cc67add32286412efcab9d0e1675a43a5c2ef3cec8879f81516ff83 | +----------------------------------------------------------+ SELECT SHA2('Maria',256); +------------------------------------------------------------------+ | SHA2('Maria',256) | +------------------------------------------------------------------+ | 9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16 | +------------------------------------------------------------------+ SELECT SHA2('Maria',0); +------------------------------------------------------------------+ | SHA2('Maria',0) | +------------------------------------------------------------------+ | 9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16 | +------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/sha2/https://mariadb.com/kb/en/sha2/ `% UNCOMPRESSSyntax ------ UNCOMPRESS(string_to_uncompress) Description ----------- Uncompresses a string compressed by the COMPRESS() function. If the argument is not a compressed value, the result is NULL. This function requires MariaDB to have been compiled with a compression library such as zlib. Otherwise, the return value is always NULL. The have_compress server system variable indicates whether a compression library is present. Examples -------- SELECT UNCOMPRESS(COMPRESS('a string')); +----------------------------------+ | UNCOMPRESS(COMPRESS('a string')) | +----------------------------------+ | a string | +----------------------------------+ SELECT UNCOMPRESS('a string'); +------------------------+ | UNCOMPRESS('a string') | +------------------------+ | NULL | +------------------------+ URL: https://mariadb.com/kb/en/uncompress/https://mariadb.com/kb/en/uncompress/. UNCOMPRESSED_LENGTHSyntax ------ UNCOMPRESSED_LENGTH(compressed_string) Description ----------- Returns the length that the compressed string had before being compressed with COMPRESS(). UNCOMPRESSED_LENGTH() returns NULL or an incorrect result if the string is not compressed. Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits. Examples -------- SELECT UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30))); +-----------------------------------------------+ | UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30))) | +-----------------------------------------------+ | 30 | +-----------------------------------------------+ URL: https://mariadb.com/kb/en/uncompressed_length/https://mariadb.com/kb/en/uncompressed_length/ %INET6_ATONINET6_ATON() has been available since MariaDB 10.0.12. Syntax ------ INET6_ATON(expr) Description ----------- Given an IPv6 or IPv4 network address as a string, returns a binary string that represents the numeric value of the address. No trailing zone ID's or traling network masks are permitted. For IPv4 addresses, or IPv6 addresses with IPv4 address parts, no classful addresses or trailing port numbers are permitted and octal numbers are not supported. The returned binary string will be VARBINARY(16) or VARBINARY(4) for IPv6 and IPv4 addresses respectively. Returns NULL if the argument is not understood. Examples -------- SELECT HEX(INET6_ATON('10.0.1.1')); +-----------------------------+ | HEX(INET6_ATON('10.0.1.1')) | +-----------------------------+ | 0A000101 | +-----------------------------+ SELECT HEX(INET6_ATON('48f3::d432:1431:ba23:846f')); +----------------------------------------------+ | HEX(INET6_ATON('48f3::d432:1431:ba23:846f')) | +----------------------------------------------+ | 48F3000000000000D4321431BA23846F | +----------------------------------------------+ URL: https://mariadb.com/kb/en/inet6_aton/https://mariadb.com/kb/en/inet6_aton/+&>>Syntax ------ value1 >> value2 Description ----------- Converts a longlong (BIGINT) number (value1) to binary and shifts value2 units to the right. Examples -------- SELECT 4 >> 2; +--------+ | 4 >> 2 | +--------+ | 1 | +--------+ URL: https://mariadb.com/kb/en/shift-right/https://mariadb.com/kb/en/shift-right/ $BIT_COUNTSyntax ------ BIT_COUNT(N) Description ----------- Returns the number of bits that are set in the argument N. Examples -------- SELECT BIT_COUNT(29), BIT_COUNT(b'101010'); +---------------+----------------------+ | BIT_COUNT(29) | BIT_COUNT(b'101010') | +---------------+----------------------+ | 4 | 3 | +---------------+----------------------+ URL: https://mariadb.com/kb/en/bit_count/https://mariadb.com/kb/en/bit_count/&^Syntax ------ ^ Description ----------- Bitwise XOR. Converts the values to binary and compares bits. If one (and only one) of the corresponding bits is 1 is the resulting bit also 1. Examples -------- SELECT 1 ^ 1; +-------+ | 1 ^ 1 | +-------+ | 0 | +-------+ SELECT 1 ^ 0; +-------+ | 1 ^ 0 | +-------+ | 1 | +-------+ SELECT 11 ^ 3; +--------+ | 11 ^ 3 | +--------+ | 8 | +--------+ URL: https://mariadb.com/kb/en/bitwise-xor/https://mariadb.com/kb/en/bitwise-xor/%|Syntax ------ | Description ----------- Bitwise OR. Converts the values to binary and compares bits. If either of the corresponding bits has a value of 1, the resulting bit is also 1. See also bitwise AND. Examples -------- SELECT 2|1; +-----+ | 2|1 | +-----+ | 3 | +-----+ SELECT 29 | 15; +---------+ | 29 | 15 | +---------+ | 31 | +---------+ URL: https://mariadb.com/kb/en/bitwise-or/https://mariadb.com/kb/en/bitwise-or/Pg!m z  nenL #GET_LOCKSyntax ------ GET_LOCK(str,timeout) Description ----------- Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. Returns 1 if the lock was obtained successfully, 0 if the attempt timed out (for example, because another client has previously locked the name), or NULL if an error occurred (such as running out of memory or the thread was killed with mysqladmin kill). A lock is released with RELEASE_LOCK(), when the connection terminates (either normally or abnormally), or before MariaDB 10.0.2, when the connection executes another GET_LOCK statement. From MariaDB 10.0.2, a connection can hold multiple locks at the same time, so a lock that is no longer needed needs to be explicitly released. The IS_FREE_LOCK function returns whether a specified lock a free or not, and the IS_USED_LOCK whether the function is in use or not. Locks obtained with GET_LOCK() do not interact with transactions. That is, committing a transaction does not release any such locks obtained during the transaction. From MariaDB 10.0.2, it is also possible to recursively set the same lock. If a lock with the same name is set n times, it needs to be released n times as well. str is case insensitive for GET_LOCK() and related functions. If str is an empty string or NULL, GET_LOCK() returns NULL and does nothing. From MariaDB 10.2.2, timeout supports microseconds. Before then, it was rounded to the closest integer. If the metadata_lock_info plugin is installed, locks acquired with this function are visible in the Information Schema METADATA_LOCK_INFO table. This function can be used to implement application locks or to simulate record locks. Names are locked on a server-wide basis. If a name has been locked by one client, GET_LOCK() blocks any request by another client for a lock with the same name. This allows clients that agree on a given lock name to use the name to perform cooperative advisory locking. But be aware that it also allows a client that is not among the set of cooperating clients to lock a name, either inadvertently or deliberately, and thus prevent any of the cooperating clients from locking that name. One way to reduce the likelihood of this is to use lock names that are database-specific or application-specific. For example, use lock names of the form db_name.str or app_name.str. Statements using the GET_LOCK() function are not safe for replication. The patch to permit multiple locks was contributed by Konstantin "Kostja" Osipov (MDEV-3917). Examples -------- SELECT GET_LOCK('lock1',10); +----------------------+ | GET_LOCK('lock1',10) | +----------------------+ | 1 | +----------------------+ SELECT IS_FREE_LOCK('lock1'), IS_USED_LOCK('lock1'); +-----------------------+-----------------------+ | IS_FREE_LOCK('lock1') | IS_USED_LOCK('lock1') | +-----------------------+-----------------------+ | 0 | 46 | +-----------------------+-----------------------+ SELECT IS_FREE_LOCK('lock2'), IS_USED_LOCK('lock2'); +-----------------------+-----------------------+ | IS_FREE_LOCK('lock2') | IS_USED_LOCK('lock2') | +-----------------------+-----------------------+ | 1 | NULL | +-----------------------+-----------------------+ From MariaDB 10.0.2, multiple locks can be held: SELECT GET_LOCK('lock2',10); +----------------------+ | GET_LOCK('lock2',10) | +----------------------+ | 1 | +----------------------+ SELECT IS_FREE_LOCK('lock1'), IS_FREE_LOCK('lock2'); +-----------------------+-----------------------+ | IS_FREE_LOCK('lock1') | IS_FREE_LOCK('lock2') | +-----------------------+-----------------------+ | 0 | 0 | +-----------------------+-----------------------+ SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2'); +-----------------------+-----------------------+ | RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') | +-----------------------+-----------------------+ | 1 | 1 | +-----------------------+-----------------------+ Before MariaDB 10.0.2, a connection could only hold a single lock: SELECT GET_LOCK('lock2',10); +----------------------+ | GET_LOCK('lock2',10) | +----------------------+ | 1 | +----------------------+ SELECT IS_FREE_LOCK('lock1'), IS_FREE_LOCK('lock2'); +-----------------------+-----------------------+ | IS_FREE_LOCK('lock1') | IS_FREE_LOCK('lock2') | +-----------------------+-----------------------+ | 1 | 0 | +-----------------------+-----------------------+ SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2'); +-----------------------+-----------------------+ | RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') | +-----------------------+-----------------------+ | NULL | 1 | +-----------------------+-----------------------+ From MariaDB 10.0.2, it is possible to hold the same lock recursively. This example is viewed using the metadata_lock_info plugin: SELECT GET_LOCK('lock3',10); +----------------------+ | GET_LOCK('lock3',10) | +----------------------+ | 1 | +----------------------+ SELECT GET_LOCK('lock3',10); +----------------------+ | GET_LOCK('lock3',10) | +----------------------+ | 1 | +----------------------+ SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO; +-----------+---------------------+---------------+-----------+--------------+------------+ | THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME | +-----------+---------------------+---------------+-----------+--------------+------------+ | 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | | +-----------+---------------------+---------------+-----------+--------------+------------+ SELECT RELEASE_LOCK('lock3'); +-----------------------+ | RELEASE_LOCK('lock3') | +-----------------------+ | 1 | +-----------------------+ SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO; +-----------+---------------------+---------------+-----------+--------------+------------+ | THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME | +-----------+---------------------+---------------+-----------+--------------+------------+ | 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | | +-----------+---------------------+---------------+-----------+--------------+------------+ SELECT RELEASE_LOCK('lock3'); +-----------------------+ | RELEASE_LOCK('lock3') | +-----------------------+ | 1 | +-----------------------+ SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO; Empty set (0.000 sec) Timeout example: Connection 1: SELECT GET_LOCK('lock4',10); +----------------------+ | GET_LOCK('lock4',10) | +----------------------+ | 1 | +----------------------+ Connection 2: SELECT GET_LOCK('lock4',10); After 10 seconds... +----------------------+ | GET_LOCK('lock4',10) | +----------------------+ | 0 | +----------------------+ Deadlocks are automatically detected and resolved. Connection 1: SELECT GET_LOCK('lock5',10); +----------------------+ | GET_LOCK('lock5',10) | +----------------------+ | 1 | +----------------------+ Connection 2: SELECT GET_LOCK('lock6',10); +----------------------+ | GET_LOCK('lock6',10) | +----------------------+ | 1 | +----------------------+ Connection 1: SELECT GET_LOCK('lock6',10); +----------------------+ | GET_LOCK('lock6',10) | +----------------------+ | 0 | +----------------------+ Connection 2: SELECT GET_LOCK('lock5',10); ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction URL: https://mariadb.com/kb/en/get_lock/https://mariadb.com/kb/en/get_lock/ Cܫ U !%INET6_NTOAINET6_NTOA() has been available from MariaDB 10.0.12. Syntax ------ INET6_NTOA(expr) Description ----------- Given an IPv6 or IPv4 network address as a numeric binary string, returns the address as a nonbinary string in the connection character set. The return string is lowercase, and is platform independent, since it does not use functions specific to the operating system. It has a maximum length of 39 characters. Returns NULL if the argument is not understood. Examples -------- SELECT INET6_NTOA(UNHEX('0A000101')); +-------------------------------+ | INET6_NTOA(UNHEX('0A000101')) | +-------------------------------+ | 10.0.1.1 | +-------------------------------+ SELECT INET6_NTOA(UNHEX('48F3000000000000D4321431BA23846F')); +-------------------------------------------------------+ | INET6_NTOA(UNHEX('48F3000000000000D4321431BA23846F')) | +-------------------------------------------------------+ | 48f3::d432:1431:ba23:846f | +-------------------------------------------------------+ URL: https://mariadb.com/kb/en/inet6_ntoa/https://mariadb.com/kb/en/inet6_ntoa/"IS_IPV4IS_IPV4() has been available since MariaDB 10.0.12. Syntax ------ IS_IPV4(expr) Description ----------- If the expression is a valid IPv4 address, returns 1, otherwise returns 0. IS_IPV4() is stricter than INET_ATON(), but as strict as INET6_ATON(), in determining the validity of an IPv4 address. This implies that if IS_IPV4 returns 1, the same expression will always return a non-NULL result when passed to INET_ATON(), but that the reverse may not apply. Examples -------- SELECT IS_IPV4('1110.0.1.1'); +-----------------------+ | IS_IPV4('1110.0.1.1') | +-----------------------+ | 0 | +-----------------------+ SELECT IS_IPV4('48f3::d432:1431:ba23:846f'); +--------------------------------------+ | IS_IPV4('48f3::d432:1431:ba23:846f') | +--------------------------------------+ | 0 | +--------------------------------------+ URL: https://mariadb.com/kb/en/is_ipv4/https://mariadb.com/kb/en/is_ipv4/)IS_IPV4_COMPATIS_IPV4_COMPAT() has been available since MariaDB 10.0.12. Syntax ------ IS_IPV4_COMPAT(expr) Description ----------- Returns 1 if a given numeric binary string IPv6 address, such as returned by INET6_ATON(), is IPv4-compatible, otherwise returns 0. Examples -------- SELECT IS_IPV4_COMPAT(INET6_ATON('::10.0.1.1')); +------------------------------------------+ | IS_IPV4_COMPAT(INET6_ATON('::10.0.1.1')) | +------------------------------------------+ | 1 | +------------------------------------------+ SELECT IS_IPV4_COMPAT(INET6_ATON('::48f3::d432:1431:ba23:846f')); +-----------------------------------------------------------+ | IS_IPV4_COMPAT(INET6_ATON('::48f3::d432:1431:ba23:846f')) | +-----------------------------------------------------------+ | 0 | +-----------------------------------------------------------+ URL: https://mariadb.com/kb/en/is_ipv4_compat/https://mariadb.com/kb/en/is_ipv4_compat/T)IS_IPV4_MAPPEDIS_IPV4_MAPPED() has been available since MariaDB 10.0.12. Syntax ------ IS_IPV4_MAPPED(expr) Description ----------- Returns 1 if a given a numeric binary string IPv6 address, such as returned by INET6_ATON(), is a valid IPv4-mapped address, otherwise returns 0. Examples -------- SELECT IS_IPV4_MAPPED(INET6_ATON('::10.0.1.1')); +------------------------------------------+ | IS_IPV4_MAPPED(INET6_ATON('::10.0.1.1')) | +------------------------------------------+ | 0 | +------------------------------------------+ SELECT IS_IPV4_MAPPED(INET6_ATON('::ffff:10.0.1.1')); +-----------------------------------------------+ | IS_IPV4_MAPPED(INET6_ATON('::ffff:10.0.1.1')) | +-----------------------------------------------+ | 1 | +-----------------------------------------------+ URL: https://mariadb.com/kb/en/is_ipv4_mapped/https://mariadb.com/kb/en/is_ipv4_mapped/Q*MASTER_POS_WAITMASTER_POS_WAIT was introduced in MariaDB 10.0.9. Syntax ------ MASTER_POS_WAIT(log_name,log_pos[,timeout,["connection_name"]]) Description ----------- This function is useful in replication for controlling master/slave synchronization. It blocks until the slave has read and applied all updates up to the specified position (log_name,log_pos) in the master log. The return value is the number of log events the slave had to wait for to advance to the specified position. The function returns NULL if the slave SQL thread is not started, the slave's master information is not initialized, the arguments are incorrect, or an error occurs. It returns -1 if the timeout has been exceeded. If the slave SQL thread stops while MASTER_POS_WAIT() is waiting, the function returns NULL. If the slave is past the specified position, the function returns immediately. If a timeout value is specified, MASTER_POS_WAIT() stops waiting when timeout seconds have elapsed. timeout must be greater than 0; a zero or negative timeout means no timeout. The connection_name is used when you are using multi-source-replication. If you don't specify it, it's set to the value of the default_master_connection system variable. Statements using the MASTER_POS_WAIT() function are not safe for replication. URL: https://mariadb.com/kb/en/master_pos_wait/https://mariadb.com/kb/en/master_pos_wait/J&~Syntax ------ ~ Description ----------- Bitwise NOT. Converts the value to 4 bytes binary and inverts all bits. Examples -------- SELECT 3 & ~1; +--------+ | 3 & ~1 | +--------+ | 2 | +--------+ SELECT 5 & ~1; +--------+ | 5 & ~1 | +--------+ | 4 | +--------+ URL: https://mariadb.com/kb/en/bitwise-not/https://mariadb.com/kb/en/bitwise-not/ %TRUE FALSEDescription ----------- The constants TRUE and FALSE evaluate to 1 and 0, respectively. The constant names can be written in any lettercase. Examples -------- SELECT TRUE, true, FALSE, false; +------+------+-------+-------+ | TRUE | TRUE | FALSE | FALSE | +------+------+-------+-------+ | 1 | 1 | 0 | 0 | +------+------+-------+-------+ URL: https://mariadb.com/kb/en/true-false/https://mariadb.com/kb/en/true-false/ %CHECK VIEWCHECK VIEW was introduced in MariaDB 10.0.18. Syntax ------ CHECK VIEW view_name Description ----------- The CHECK VIEW statement was introduced in MariaDB 10.0.18 to assist with fixing MDEV-6916, an issue introduced in MariaDB 5.2 where the view algorithms were swapped. It checks whether the view algorithm is correct. It is run as part of mysql_upgrade, and should not normally be required in regular use. URL: https://mariadb.com/kb/en/check-view/https://mariadb.com/kb/en/check-view/ .)URL: https://mariadb.com/kb/en/checksum-table/https://mariadb.com/kb/en/checksum-table/ H3BLOB and TEXT Data TypesDescription ----------- A BLOB is a binary large object that can hold a variable amount of data. The four BLOB types are TINYBLOB, BLOB, MEDIUMBLOB, and LONGBLOB. These differ only in the maximum length of the values they can hold. The TEXT types are TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT. JSON (alias for LONGTEXT) These correspond to the four BLOB types and have the same maximum lengths and storage requirements. Starting from MariaDB 10.2.1, BLOB and TEXT columns can have a DEFAULT value. URL: https://mariadb.com/kb/en/blob-and-text-data-types/https://mariadb.com/kb/en/blob-and-text-data-types/zdp   'j ^yZ+MASTER_GTID_WAITMASTER_GTID_WAIT() was included in MariaDB 10.0.9. Syntax ------ MASTER_GTID_WAIT(gtid-list[, timeout) Description ----------- This function takes a string containing a comma-separated list of global transaction id's (similar to the value of, for example, gtid_binlog_pos). It waits until the value of gtid_slave_pos has the same or higher seq_no within all replication domains specified in the gtid-list; in other words, it waits until the slave has reached the specified GTID position. An optional second argument gives a timeout in seconds. If the timeout expires before the specified GTID position is reached, then the function returns -1. Passing NULL or a negative number for the timeout means no timeout, and the function will wait indefinitely. If the wait completes without a timeout, 0 is returned. Passing NULL for the gtid-list makes the function return NULL immediately, without waiting. The gtid-list may be the empty string, in which case MASTER_GTID_WAIT() returns immediately. If the gtid-list contains fewer domains than gtid_slave_pos, then only those domains are waited upon. If gtid-list contains a domain that is not present in @@gtid_slave_pos, then MASTER_GTID_WAIT() will wait until an event containing such domain_id arrives on the slave (or until timed out or killed). MASTER_GTID_WAIT() can be useful to ensure that a slave has caught up to a master. Simply take the value of gtid_binlog_pos on the master, and use it in a MASTER_GTID_WAIT() call on the slave; when the call completes, the slave will have caught up with that master position. MASTER_GTID_WAIT() can also be used in client applications together with the last_gtid session variable. This is useful in a read-scaleout replication setup, where the application writes to a single master but divides the reads out to a number of slaves to distribute the load. In such a setup, there is a risk that an application could first do an update on the master, and then a bit later do a read on a slave, and if the slave is not fast enough, the data read from the slave might not include the update just made, possibly confusing the application and/or the end-user. One way to avoid this is to request the value of last_gtid on the master just after the update. Then before doing the read on the slave, do a MASTER_GTID_WAIT() on the value obtained from the master; this will ensure that the read is not performed until the slave has replicated sufficiently far for the update to have become visible. Note that MASTER_GTID_WAIT() can be used even if the slave is configured not to use GTID for connections (CHANGE MASTER TO master_use_gtid=no). This is because from MariaDB 10, GTIDs are always logged on the master server, and always recorded on the slave servers. Differences to MASTER_POS_WAIT() MASTER_GTID_WAIT() is global; it waits for any master connection to reach the specified GTID position. MASTER_POS_WAIT() works only against a specific connection. This also means that while MASTER_POS_WAIT() aborts if its master connection is terminated with STOP SLAVE or due to an error, MASTER_GTID_WAIT() continues to wait while slaves are stopped. MASTER_GTID_WAIT() can take its timeout as a floating-point value, so a timeout in fractional seconds is supported, eg. MASTER_GTID_WAIT("0-1-100", 0.5). (The minimum wait is one microsecond, 0.000001 seconds). MASTER_GTID_WAIT() allows one to specify a timeout of zero in order to do a non-blocking check to see if the slaves have progressed to a specific GTID position (MASTER_POS_WAIT() takes a zero timeout as meaning an infinite wait). To do an infinite MASTER_GTID_WAIT(), specify a negative timeout, or omit the timeout argument. MASTER_GTID_WAIT() does not return the number of events executed since the wait started, nor does it return NULL if a slave thread is stopped. It always returns either 0 for successful wait completed, or -1 for timeout reached (or NULL if the specified gtid-pos is NULL). Since MASTER_GTID_WAIT() looks only at the seq_no part of the GTIDs, not the server_id, care is needed if a slave becomes diverged from another server so that two different GTIDs with the same seq_no (in the same domain) arrive at the same server. This situation is in any case best avoided; setting gtid_strict_mode is recommended, as this will prevent any such out-of-order sequence numbers from ever being replicated on a slave. URL: https://mariadb.com/kb/en/master_gtid_wait/https://mariadb.com/kb/en/master_gtid_wait/UUIDSyntax ------ UUID() Description ----------- Returns a Universal Unique Identifier (UUID) generated according to "DCE 1.1: Remote Procedure Call" (Appendix A) CAE (Common Applications Environment) Specifications published by The Open Group in October 1997 (Document Number C706). A UUID is designed as a number that is globally unique in space and time. Two calls to UUID() are expected to generate two different values, even if these calls are performed on two separate computers that are not connected to each other. A UUID is a 128-bit number represented by a utf8 string of five hexadecimal numbers in aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee format: The first three numbers are generated from a timestamp. The fourth number preserves temporal uniqueness in case the timestamp value loses monotonicity (for example, due to daylight saving time). The fifth number is an IEEE 802 node number that provides spatial uniqueness. A random number is substituted if the latter is not available (for example, because the host computer has no Ethernet card, or we do not know how to find the hardware address of an interface on your operating system). In this case, spatial uniqueness cannot be guaranteed. Nevertheless, a collision should have very low probability. Currently, the MAC address of an interface is taken into account only on FreeBSD and Linux. On other operating systems, MariaDB uses a randomly generated 48-bit number. Statements using the UUID() function are not safe for replication. UUID() results are intended to be unique, but cannot always be relied upon to unpredictable and unguessable, so should not be relied upon for these purposes. Examples -------- SELECT UUID(); +--------------------------------------+ | UUID() | +--------------------------------------+ | cd41294a-afb0-11df-bc9b-00241dd75637 | +--------------------------------------+ URL: https://mariadb.com/kb/en/uuid/https://mariadb.com/kb/en/uuid/ $CHAR BYTEDescription ----------- The CHAR BYTE data type is an alias for the BINARY data type. This is a compatibility feature. URL: https://mariadb.com/kb/en/char-byte/https://mariadb.com/kb/en/char-byte/#LONGBLOBSyntax ------ LONGBLOB Description ----------- A BLOB column with a maximum length of 4,294,967,295 bytes or 4GB (232 - 1). The effective maximum length of LONGBLOB columns depends on the configured maximum packet size in the client/server protocol and available memory. Each LONGBLOB value is stored using a four-byte length prefix that indicates the number of bytes in the value. Oracle Mode In Oracle mode from MariaDB 10.3, BLOB is a synonym for LONGBLOB. URL: https://mariadb.com/kb/en/longblob/https://mariadb.com/kb/en/longblob/#LONGTEXTSyntax ------ LONGTEXT [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- A TEXT column with a maximum length of 4,294,967,295 or 4GB (232 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. The effective maximum length of LONGTEXT columns also depends on the configured maximum packet size in the client/server protocol and available memory. Each LONGTEXT value is stored using a four-byte length prefix that indicates the number of bytes in the value. From MariaDB 10.2.7, JSON is an alias for LONGTEXT. See JSON Data Type for details. Oracle Mode In Oracle mode from MariaDB 10.3, CLOB is a synonym for LONGTEXT. URL: https://mariadb.com/kb/en/longtext/https://mariadb.com/kb/en/longtext/!}: .UUm 'RELEASE_LOCKSyntax ------ RELEASE_LOCK(str) Description ----------- Releases the lock named by the string str that was obtained with GET_LOCK(). Returns 1 if the lock was released, 0 if the lock was not established by this thread (in which case the lock is not released), and NULL if the named lock did not exist. The lock does not exist if it was never obtained by a call to GET_LOCK() or if it has previously been released. MariaDB until 10.0.1 Before 10.0.2, GET_LOCK() released the existing lock, if any. Since 10.0.2 this does not happen, because multiple locks are allowed. str is case insensitive. If str is an empty string or NULL, RELEASE_LOCK() returns NULL and does nothing. Statements using the RELEASE_LOCK() function are not safe for replication. The DO statement is convenient to use with RELEASE_LOCK(). Examples -------- Connection1: SELECT GET_LOCK('lock1',10); +----------------------+ | GET_LOCK('lock1',10) | +----------------------+ | 1 | +----------------------+ Connection 2: SELECT GET_LOCK('lock2',10); +----------------------+ | GET_LOCK('lock2',10) | +----------------------+ | 1 | +----------------------+ Connection 1: SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2'), RELEASE_LOCK('lock3'); +-----------------------+-----------------------+-----------------------+ | RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') | RELEASE_LOCK('lock3') | +-----------------------+-----------------------+-----------------------+ | 1 | 0 | NULL | +-----------------------+-----------------------+-----------------------+ From MariaDB 10.0.2, it is possible to hold the same lock recursively. This example is viewed using the metadata_lock_info plugin: SELECT GET_LOCK('lock3',10); +----------------------+ | GET_LOCK('lock3',10) | +----------------------+ | 1 | +----------------------+ SELECT GET_LOCK('lock3',10); +----------------------+ | GET_LOCK('lock3',10) | +----------------------+ | 1 | +----------------------+ SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO; +-----------+---------------------+---------------+-----------+--------------+------------+ | THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME | +-----------+---------------------+---------------+-----------+--------------+------------+ | 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | | +-----------+---------------------+---------------+-----------+--------------+------------+ SELECT RELEASE_LOCK('lock3'); +-----------------------+ | RELEASE_LOCK('lock3') | +-----------------------+ | 1 | +-----------------------+ SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO; +-----------+---------------------+---------------+-----------+--------------+------------+ | THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME | +-----------+---------------------+---------------+-----------+--------------+------------+ | 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | | +-----------+---------------------+---------------+-----------+--------------+------------+ SELECT RELEASE_LOCK('lock3'); +-----------------------+ | RELEASE_LOCK('lock3') | +-----------------------+ | 1 | +-----------------------+ SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO; Empty set (0.000 sec) URL: https://mariadb.com/kb/en/release_lock/https://mariadb.com/kb/en/release_lock/'VALUES / VALUESyntax ------ VALUE(col_name) MariaDB until 10.3.2 VALUES(col_name) Description ----------- In an INSERT ... ON DUPLICATE KEY UPDATE statement, you can use the VALUES(col_name) function in the UPDATE clause to refer to column values from the INSERT portion of the statement. In other words, VALUES(col_name) in the UPDATE clause refers to the value of col_name that would be inserted, had no duplicate-key conflict occurred. This function is especially useful in multiple-row inserts. The VALUES() function is meaningful only in INSERT ... ON DUPLICATE KEY UPDATE statements and returns NULL otherwise. In MariaDB 10.3.3 this function was renamed to VALUE(), because it's incompatible with the standard Table Value Constructors syntax, implemented in MariaDB 10.3.3. The VALUES() function can still be used even from MariaDB 10.3.3, but only in INSERT ... ON DUPLICATE KEY UPDATE statements; it's a syntax error otherwise. Examples -------- INSERT INTO t (a,b,c) VALUES (1,2,3),(4,5,6) ON DUPLICATE KEY UPDATE c=VALUE(a)+VALUE(b); MariaDB until 10.3.2 INSERT INTO t (a,b,c) VALUES (1,2,3),(4,5,6) ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b); URL: https://mariadb.com/kb/en/values-value/https://mariadb.com/kb/en/values-value/||Syntax ------ OR, || Description ----------- Logical OR. When both operands are non-NULL, the result is 1 if any operand is non-zero, and 0 otherwise. With a NULL operand, the result is 1 if the other operand is non-zero, and NULL otherwise. If both operands are NULL, the result is NULL. For this operator, short-circuit evaluation can be used. Note that, if the PIPES_AS_CONCAT SQL_MODE is set, || is used as a string concatenation operator. This means that a || b is the same as CONCAT(a,b). See CONCAT() for details. Oracle Mode In Oracle mode from MariaDB 10.3, || ignores NULL. Examples -------- SELECT 1 || 1; +--------+ | 1 || 1 | +--------+ | 1 | +--------+ SELECT 1 || 0; +--------+ | 1 || 0 | +--------+ | 1 | +--------+ SELECT 0 || 0; +--------+ | 0 || 0 | +--------+ | 0 | +--------+ SELECT 0 || NULL; +-----------+ | 0 || NULL | +-----------+ | NULL | +-----------+ SELECT 1 || NULL; +-----------+ | 1 || NULL | +-----------+ | 1 | +-----------+ In Oracle mode, from MariaDB 10.3: SELECT 0 || NULL; +-----------+ | 0 || NULL | +-----------+ | 0 | +-----------+ URL: https://mariadb.com/kb/en/or/https://mariadb.com/kb/en/or/ %MEDIUMBLOBSyntax ------ MEDIUMBLOB Description ----------- A BLOB column with a maximum length of 16,777,215 (224 - 1) bytes. Each MEDIUMBLOB value is stored using a three-byte length prefix that indicates the number of bytes in the value. URL: https://mariadb.com/kb/en/mediumblob/https://mariadb.com/kb/en/mediumblob/ %MEDIUMTEXTSyntax ------ MEDIUMTEXT [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- A TEXT column with a maximum length of 16,777,215 (224 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. Each MEDIUMTEXT value is stored using a three-byte length prefix that indicates the number of bytes in the value. URL: https://mariadb.com/kb/en/mediumtext/https://mariadb.com/kb/en/mediumtext/2ROWThe ROW data type was introduced in MariaDB 10.3.0. Syntax ------ ROW ( [{, }... ]) Description ----------- ROW is a data type for stored procedure variables. Features ROW fields as normal variables ROW fields (members) act as normal variables, and are able to appear in all query parts where a stored procedure variable is allowed: Assignment is using the := operator and the SET command: a.x:= 10; a.x:= b.x; SET a.x= 10, a.y=20, a.z= b.z; Passing to functions and operators: SELECT f1(rec.a), rec.a URL: https://mariadb.com/kb/en/row/https://mariadb.com/kb/en/row/  (SET Data TypeSyntax ------ SET('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- A set. A string object that can have zero or more values, each of which must be chosen from the list of values 'value1', 'value2', ... A SET column can have a maximum of 64 members. SET values are represented internally as integers. URL: https://mariadb.com/kb/en/set-data-type/https://mariadb.com/kb/en/set-data-type/:aWVTB  6 +@CAssignment Operator (=)Syntax ------ identifier = expr Description ----------- The equal sign is used as both an assignment operator in certain contexts, and as a comparison operator. When used as assignment operator, the value on the right is assigned to the variable (or column, in some contexts) on the left. Since its use can be ambiguous, unlike the := assignment operator, the = assignment operator cannot be used in all contexts, and is only valid as part of a SET statement, or the SET clause of an UPDATE statement This operator works with both user-defined variables and local variables. Examples -------- UPDATE table_name SET x = 2 WHERE x > 100; SET @x = 1, @y := 2; URL: https://mariadb.com/kb/en/assignment-operators-assignment-operator/https://mariadb.com/kb/en/assignment-operators-assignment-operator/ 5Stored Aggregate FunctionsThe ability to create stored aggregate functions was added in MariaDB 10.3.3. Aggregate functions are functions that are computed over a sequence of rows and return one result for the sequence of rows. Creating a custom aggregate function is done using the CREATE FUNCTION statement with two main differences: The addition of the AGGREGATE keyword, so CREATE AGGREGATE FUNCTION The FETCH GROUP NEXT ROW instruction inside the loop Oracle PL/SQL compatibility using SQL/PL is provided Standard Syntax CREATE AGGREGATE FUNCTION function_name (parameters) RETURNS return_type BEGIN All types of declarations DECLARE CONTINUE HANDLER FOR NOT FOUND RETURN return_val; LOOP FETCH GROUP NEXT ROW; // fetches next row from table other instructions END LOOP; END Stored aggregate functions were a 2016 Google Summer of Code project by Varun Gupta. Using SQL/PL SET sql_mode=Oracle; DELIMITER // CREATE AGGREGATE FUNCTION function_name (parameters) RETURN return_type declarations BEGIN LOOP FETCH GROUP NEXT ROW; -- fetches next row from table -- other instructions END LOOP; EXCEPTION WHEN NO_DATA_FOUND THEN RETURN return_val; END // DELIMITER ; Examples -------- First a simplified example: CREATE TABLE marks(stud_id INT, grade_count INT); INSERT INTO marks VALUES (1,6), (2,4), (3,7), (4,5), (5,8); SELECT * FROM marks; +---------+-------------+ | stud_id | grade_count | +---------+-------------+ | 1 | 6 | | 2 | 4 | | 3 | 7 | | 4 | 5 | | 5 | 8 | +---------+-------------+ DELIMITER // CREATE AGGREGATE FUNCTION IF NOT EXISTS aggregate_count(x INT) RETURNS INT BEGIN DECLARE count_students INT DEFAULT 0; DECLARE CONTINUE HANDLER FOR NOT FOUND RETURN count_students; LOOP FETCH GROUP NEXT ROW; IF x THEN SET count_students = count_students+1; END IF; END LOOP; END // DELIMITER ; A non-trivial example that cannot easily be rewritten using existing functions: DELIMITER // CREATE AGGREGATE FUNCTION medi_int(x INT) RETURNS DOUBLE BEGIN DECLARE CONTINUE HANDLER FOR NOT FOUND BEGIN DECLARE res DOUBLE; DECLARE cnt INT DEFAULT (SELECT COUNT(*) FROM tt); DECLARE lim INT DEFAULT (cnt-1) DIV 2; IF cnt % 2 = 0 THEN SET res = (SELECT AVG(a) FROM (SELECT a FROM tt ORDER BY a LIMIT lim,2) ttt); ELSE SET res = (SELECT a FROM tt ORDER BY a LIMIT lim,1); END IF; DROP TEMPORARY TABLE tt; RETURN res; END; CREATE TEMPORARY TABLE tt (a INT); LOOP FETCH GROUP NEXT ROW; INSERT INTO tt VALUES (x); END LOOP; END // DELIMITER ; SQL/PL Example This uses the same marks table as created above. SET sql_mode=Oracle; DELIMITER // CREATE AGGREGATE FUNCTION aggregate_count(x INT) RETURN INT AS count_students INT DEFAULT 0; BEGIN LOOP FETCH GROUP NEXT ROW; IF x THEN SET count_students := count_students+1; END IF; END LOOP; EXCEPTION WHEN NO_DATA_FOUND THEN RETURN count_students; END aggregate_count // DELIMITER ; SELECT aggregate_count(stud_id) FROM marks; URL: https://mariadb.com/kb/en/stored-aggregate-functions/https://mariadb.com/kb/en/stored-aggregate-functions/: AVGSyntax ------ AVG([DISTINCT] expr) Description ----------- Returns the average value of expr. The DISTINCT option can be used to return the average of the distinct values of expr. NULL values are ignored. It is an aggregate function, and so can be used with the GROUP BY clause. AVG() returns NULL if there were no matching rows. From MariaDB 10.2.0, AVG() can be used as a window function. Examples -------- CREATE TABLE sales (sales_value INT); INSERT INTO sales VALUES(10),(20),(20),(40); SELECT AVG(sales_value) FROM sales; +------------------+ | AVG(sales_value) | +------------------+ | 22.5000 | +------------------+ SELECT AVG(DISTINCT(sales_value)) FROM sales; +----------------------------+ | AVG(DISTINCT(sales_value)) | +----------------------------+ | 23.3333 | +----------------------------+ Commonly, AVG() is used with a GROUP BY clause: CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83); SELECT name, AVG(score) FROM student GROUP BY name; +---------+------------+ | name | AVG(score) | +---------+------------+ | Chun | 74.0000 | | Esben | 37.0000 | | Kaolin | 72.0000 | | Tatiana | 85.0000 | +---------+------------+ Be careful to avoid this common mistake, not grouping correctly and returning mismatched data: SELECT name,test,AVG(score) FROM student; +------+------+------------+ | name | test | MIN(score) | +------+------+------------+ | Chun | SQL | 31 | +------+------+------------+ As a window function: CREATE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83); SELECT name, test, score, AVG(score) OVER (PARTITION BY test) AS average_by_test FROM student_test; +---------+--------+-------+-----------------+ | name | test | score | average_by_test | +---------+--------+-------+-----------------+ | Chun | SQL | 75 | 65.2500 | | Chun | Tuning | 73 | 68.7500 | | Esben | SQL | 43 | 65.2500 | | Esben | Tuning | 31 | 68.7500 | | Kaolin | SQL | 56 | 65.2500 | | Kaolin | Tuning | 88 | 68.7500 | | Tatiana | SQL | 87 | 65.2500 | | Tatiana | Tuning | 83 | 68.7500 | +---------+--------+-------+-----------------+ URL: https://mariadb.com/kb/en/avg/https://mariadb.com/kb/en/avg/% F$TIMESTAMPSyntax ------ TIMESTAMP [( URL: https://mariadb.com/kb/en/timestamp/https://mariadb.com/kb/en/timestamp/& #TINYBLOBSyntax ------ TINYBLOB Description ----------- A BLOB column with a maximum length of 255 (28 - 1) bytes. Each TINYBLOB value is stored using a one-byte length prefix that indicates the number of bytes in the value. URL: https://mariadb.com/kb/en/tinyblob/https://mariadb.com/kb/en/tinyblob/(#TINYTEXTSyntax ------ TINYTEXT [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- A TEXT column with a maximum length of 255 (28 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. Each TINYTEXT value is stored using a one-byte length prefix that indicates the number of bytes in the value. URL: https://mariadb.com/kb/en/tinytext/https://mariadb.com/kb/en/tinytext/Bi n< b""BIT_ANDSyntax ------ BIT_AND(expr) Description ----------- Returns the bitwise AND of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.0, BIT_AND() can be used as a window function. Examples -------- CREATE TABLE vals (x INT); INSERT INTO vals VALUES(111),(110),(100); SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals; +------------+-----------+------------+ | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) | +------------+-----------+------------+ | 100 | 111 | 101 | +------------+-----------+------------+ As an aggregate function: CREATE TABLE vals2 (category VARCHAR(1), x INT); INSERT INTO vals2 VALUES ('a',111),('a',110),('a',100), ('b','000'),('b',001),('b',011); SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals GROUP BY category; +----------+------------+-----------+------------+ | category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) | +----------+------------+-----------+------------+ | a | 100 | 111 | 101 | | b | 0 | 11 | 10 | +----------+------------+-----------+------------+ URL: https://mariadb.com/kb/en/bit_and/https://mariadb.com/kb/en/bit_and/!BIT_ORSyntax ------ BIT_OR(expr) Description ----------- Returns the bitwise OR of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.0, BIT_OR can be used as a window function. Examples -------- CREATE TABLE vals (x INT); INSERT INTO vals VALUES(111),(110),(100); SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals; +------------+-----------+------------+ | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) | +------------+-----------+------------+ | 100 | 111 | 101 | +------------+-----------+------------+ As an aggregate function: CREATE TABLE vals2 (category VARCHAR(1), x INT); INSERT INTO vals2 VALUES ('a',111),('a',110),('a',100), ('b','000'),('b',001),('b',011); SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals GROUP BY category; +----------+------------+-----------+------------+ | category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) | +----------+------------+-----------+------------+ | a | 100 | 111 | 101 | | b | 0 | 11 | 10 | +----------+------------+-----------+------------+ URL: https://mariadb.com/kb/en/bit_or/https://mariadb.com/kb/en/bit_or/"BIT_XORSyntax ------ BIT_XOR(expr) Description ----------- Returns the bitwise XOR of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.0, BIT_XOR() can be used as a window function. Examples -------- CREATE TABLE vals (x INT); INSERT INTO vals VALUES(111),(110),(100); SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals; +------------+-----------+------------+ | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) | +------------+-----------+------------+ | 100 | 111 | 101 | +------------+-----------+------------+ As an aggregate function: CREATE TABLE vals2 (category VARCHAR(1), x INT); INSERT INTO vals2 VALUES ('a',111),('a',110),('a',100), ('b','000'),('b',001),('b',011); SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals GROUP BY category; +----------+------------+-----------+------------+ | category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) | +----------+------------+-----------+------------+ | a | 100 | 111 | 101 | | b | 0 | 11 | 10 | +----------+------------+-----------+------------+ URL: https://mariadb.com/kb/en/bit_xor/https://mariadb.com/kb/en/bit_xor/@ COUNTSyntax ------ COUNT(expr) Description ----------- Returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement. The result is a BIGINT value. It is an aggregate function, and so can be used with the GROUP BY clause. COUNT(*) counts the total number of rows in a table. COUNT() returns 0 if there were no matching rows. From MariaDB 10.2.0, COUNT() can be used as a window function. Examples -------- CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83); SELECT COUNT(*) FROM student; +----------+ | COUNT(*) | +----------+ | 8 | +----------+ COUNT(DISTINCT) example: SELECT COUNT(DISTINCT (name)) FROM student; +------------------------+ | COUNT(DISTINCT (name)) | +------------------------+ | 4 | +------------------------+ As a window function CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, COUNT(score) OVER (PARTITION BY name) AS tests_written FROM student_test; +---------+--------+-------+---------------+ | name | test | score | tests_written | +---------+--------+-------+---------------+ | Chun | SQL | 75 | 2 | | Chun | Tuning | 73 | 2 | | Esben | SQL | 43 | 2 | | Esben | Tuning | 31 | 2 | | Kaolin | SQL | 56 | 2 | | Kaolin | Tuning | 88 | 2 | | Tatiana | SQL | 87 | 1 | +---------+--------+-------+---------------+ URL: https://mariadb.com/kb/en/count/https://mariadb.com/kb/en/count/.p CLOSESyntax ------ CLOSE cursor_name Description ----------- This statement closes a previously opened cursor. The cursor must have been previously opened or else an error occurs. If not closed explicitly, a cursor is closed at the end of the compound statement in which it was declared. See Cursor Overview for an example. URL: https://mariadb.com/kb/en/close/https://mariadb.com/kb/en/close/0?)DECLARE CURSORSyntax ------ URL: https://mariadb.com/kb/en/declare-cursor/https://mariadb.com/kb/en/declare-cursor/3 FETCHSyntax ------ FETCH cursor_name INTO var_name [, var_name] ... Description ----------- This statement fetches the next row (if a row exists) using the specified open cursor, and advances the cursor pointer. var_name can be a local variable, but not a user-defined variable. If no more rows are available, a No Data condition occurs with SQLSTATE value 02000. To detect this condition, you can set up a handler for it (or for a NOT FOUND condition). See Cursor Overview for an example. URL: https://mariadb.com/kb/en/fetch/https://mariadb.com/kb/en/fetch/5pGOTOThe GOTO statement was introduced in MariaDB 10.3 for Oracle compatibility. Syntax ------ GOTO label Description ----------- The GOTO statement causes the code to jump to the specified label, and continue operating from there. It is only accepted when in Oracle mode. Example SET sql_mode=ORACLE; DELIMITER // CREATE OR REPLACE PROCEDURE p1 AS BEGIN SELECT 1; GOTO label; SELECT 2; SELECT 3; END; // DELIMITER call p1(); +---+ | 1 | +---+ | 1 | +---+ 1 row in set (0.000 sec) +---+ | 3 | +---+ | 3 | +---+ 1 row in set (0.000 sec) URL: https://mariadb.com/kb/en/goto/https://mariadb.com/kb/en/goto/bK}s  p$9$\? MAXSyntax ------ MAX([DISTINCT] expr) Description ----------- Returns the largest, or maximum, value of expr. MAX() can also take a string argument in which case it returns the maximum string value. The DISTINCT keyword can be used to find the maximum of the distinct values of expr, however, this produces the same result as omitting DISTINCT. Note that SET and ENUM fields are currently compared by their string value rather than their relative position in the set, so MAX() may produce a different highest result than ORDER BY DESC. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, MAX() can be used as a window function. MAX() returns NULL if there were no matching rows. Examples -------- CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83); SELECT name, MAX(score) FROM student GROUP BY name; +---------+------------+ | name | MAX(score) | +---------+------------+ | Chun | 75 | | Esben | 43 | | Kaolin | 88 | | Tatiana | 87 | +---------+------------+ MAX string: SELECT MAX(name) FROM student; +-----------+ | MAX(name) | +-----------+ | Tatiana | +-----------+ Be careful to avoid this common mistake, not grouping correctly and returning mismatched data: SELECT name,test,MAX(SCORE) FROM student; +------+------+------------+ | name | test | MAX(SCORE) | +------+------+------------+ | Chun | SQL | 88 | +------+------+------------+ Difference between ORDER BY DESC and MAX(): CREATE TABLE student2(name CHAR(10),grade ENUM('b','c','a')); INSERT INTO student2 VALUES('Chun','b'),('Esben','c'),('Kaolin','a'); SELECT MAX(grade) FROM student2; +------------+ | MAX(grade) | +------------+ | c | +------------+ SELECT grade FROM student2 ORDER BY grade DESC LIMIT 1; +-------+ | grade | +-------+ | a | +-------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, MAX(score) OVER (PARTITION BY name) AS highest_score FROM student_test; +---------+--------+-------+---------------+ | name | test | score | highest_score | +---------+--------+-------+---------------+ | Chun | SQL | 75 | 75 | | Chun | Tuning | 73 | 75 | | Esben | SQL | 43 | 43 | | Esben | Tuning | 31 | 43 | | Kaolin | SQL | 56 | 88 | | Kaolin | Tuning | 88 | 88 | | Tatiana | SQL | 87 | 87 | +---------+--------+-------+---------------+ URL: https://mariadb.com/kb/en/max/https://mariadb.com/kb/en/max/+ MINSyntax ------ MIN([DISTINCT] expr) Description ----------- Returns the minimum value of expr. MIN() may take a string argument, in which case it returns the minimum string value. The DISTINCT keyword can be used to find the minimum of the distinct values of expr, however, this produces the same result as omitting DISTINCT. Note that SET and ENUM fields are currently compared by their string value rather than their relative position in the set, so MIN() may produce a different lowest result than ORDER BY ASC. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, MIN() can be used as a window function. MIN() returns NULL if there were no matching rows. Examples -------- CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83); SELECT name, MIN(score) FROM student GROUP BY name; +---------+------------+ | name | MIN(score) | +---------+------------+ | Chun | 73 | | Esben | 31 | | Kaolin | 56 | | Tatiana | 83 | +---------+------------+ MIN() with a string: SELECT MIN(name) FROM student; +-----------+ | MIN(name) | +-----------+ | Chun | +-----------+ Be careful to avoid this common mistake, not grouping correctly and returning mismatched data: SELECT name,test,MIN(score) FROM student; +------+------+------------+ | name | test | MIN(score) | +------+------+------------+ | Chun | SQL | 31 | +------+------+------------+ Difference between ORDER BY ASC and MIN(): CREATE TABLE student2(name CHAR(10),grade ENUM('b','c','a')); INSERT INTO student2 VALUES('Chun','b'),('Esben','c'),('Kaolin','a'); SELECT MIN(grade) FROM student2; +------------+ | MIN(grade) | +------------+ | a | +------------+ SELECT grade FROM student2 ORDER BY grade ASC LIMIT 1; +-------+ | grade | +-------+ | b | +-------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, MIN(score) OVER (PARTITION BY name) AS lowest_score FROM student_test; +---------+--------+-------+--------------+ | name | test | score | lowest_score | +---------+--------+-------+--------------+ | Chun | SQL | 75 | 73 | | Chun | Tuning | 73 | 73 | | Esben | SQL | 43 | 31 | | Esben | Tuning | 31 | 31 | | Kaolin | SQL | 56 | 56 | | Kaolin | Tuning | 88 | 56 | | Tatiana | SQL | 87 | 87 | +---------+--------+-------+--------------+ URL: https://mariadb.com/kb/en/min/https://mariadb.com/kb/en/min/6IFSyntax ------ IF search_condition THEN statement_list [ELSEIF search_condition THEN statement_list] ... [ELSE statement_list] END IF; Description ----------- IF implements a basic conditional construct. If the search_condition evaluates to true, the corresponding SQL statement list is executed. If no search_condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements. URL: https://mariadb.com/kb/en/if/https://mariadb.com/kb/en/if/7"ITERATESyntax ------ ITERATE label ITERATE can appear only within LOOP, REPEAT, and WHILE statements. ITERATE means "do the loop again", and uses the statement's label to determine which statements to repeat. The label must be in the same stored program, not in a caller procedure. If you try to use ITERATE with a non-existing label, or if the label is associated to a construct which is not a loop, the following error will be produced: ERROR 1308 (42000): ITERATE with no matching label: Below is an example of how ITERATE might be used: CREATE PROCEDURE doiterate(p1 INT) BEGIN label1: LOOP SET p1 = p1 + 1; IF p1 URL: https://mariadb.com/kb/en/iterate/https://mariadb.com/kb/en/iterate/:LOOPSyntax ------ [begin_label:] LOOP statement_list END LOOP [end_label] Description ----------- LOOP implements a simple loop construct, enabling repeated execution of the statement list, which consists of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter. The statements within the loop are repeated until the loop is exited; usually this is accomplished with a LEAVE statement. A LOOP statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same. See Delimiters in the mysql client for more on delimiter usage in the client. URL: https://mariadb.com/kb/en/loop/https://mariadb.com/kb/en/loop/ z Z n *`STDSyntax ------ STD(expr) Description ----------- Returns the population standard deviation of expr. This is an extension to standard SQL. The standard SQL function STDDEV_POP() can be used instead. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, STD() can be used as a window function. This function returns NULL if there were no matching rows. Examples -------- As an aggregate function: CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT); INSERT INTO stats VALUES ('a',1),('a',2),('a',3), ('b',11),('b',12),('b',20),('b',30),('b',60); SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) FROM stats GROUP BY category; +----------+---------------+----------------+------------+ | category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) | +----------+---------------+----------------+------------+ | a | 0.8165 | 1.0000 | 0.6667 | | b | 18.0400 | 20.1693 | 325.4400 | +----------+---------------+----------------+------------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, STDDEV_POP(score) OVER (PARTITION BY test) AS stddev_results FROM student_test; +---------+--------+-------+----------------+ | name | test | score | stddev_results | +---------+--------+-------+----------------+ | Chun | SQL | 75 | 16.9466 | | Chun | Tuning | 73 | 24.1247 | | Esben | SQL | 43 | 16.9466 | | Esben | Tuning | 31 | 24.1247 | | Kaolin | SQL | 56 | 16.9466 | | Kaolin | Tuning | 88 | 24.1247 | | Tatiana | SQL | 87 | 16.9466 | +---------+--------+-------+----------------+ URL: https://mariadb.com/kb/en/std/https://mariadb.com/kb/en/std/{!STDDEVSyntax ------ STDDEV(expr) Description ----------- Returns the population standard deviation of expr. This function is provided for compatibility with Oracle. The standard SQL function STDDEV_POP() can be used instead. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, STDDEV() can be used as a window function. This function returns NULL if there were no matching rows. Examples -------- As an aggregate function: CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT); INSERT INTO stats VALUES ('a',1),('a',2),('a',3), ('b',11),('b',12),('b',20),('b',30),('b',60); SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) FROM stats GROUP BY category; +----------+---------------+----------------+------------+ | category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) | +----------+---------------+----------------+------------+ | a | 0.8165 | 1.0000 | 0.6667 | | b | 18.0400 | 20.1693 | 325.4400 | +----------+---------------+----------------+------------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, STDDEV_POP(score) OVER (PARTITION BY test) AS stddev_results FROM student_test; +---------+--------+-------+----------------+ | name | test | score | stddev_results | +---------+--------+-------+----------------+ | Chun | SQL | 75 | 16.9466 | | Chun | Tuning | 73 | 24.1247 | | Esben | SQL | 43 | 16.9466 | | Esben | Tuning | 31 | 24.1247 | | Kaolin | SQL | 56 | 16.9466 | | Kaolin | Tuning | 88 | 24.1247 | | Tatiana | SQL | 87 | 16.9466 | +---------+--------+-------+----------------+ URL: https://mariadb.com/kb/en/stddev/https://mariadb.com/kb/en/stddev/ %STDDEV_POPSyntax ------ STDDEV_POP(expr) Description ----------- Returns the population standard deviation of expr (the square root of VAR_POP()). You can also use STD() or STDDEV(), which are equivalent but not standard SQL. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, STDDEV_POP() can be used as a window function. STDDEV_POP() returns NULL if there were no matching rows. Examples -------- As an aggregate function: CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT); INSERT INTO stats VALUES ('a',1),('a',2),('a',3), ('b',11),('b',12),('b',20),('b',30),('b',60); SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) FROM stats GROUP BY category; +----------+---------------+----------------+------------+ | category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) | +----------+---------------+----------------+------------+ | a | 0.8165 | 1.0000 | 0.6667 | | b | 18.0400 | 20.1693 | 325.4400 | +----------+---------------+----------------+------------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, STDDEV_POP(score) OVER (PARTITION BY test) AS stddev_results FROM student_test; +---------+--------+-------+----------------+ | name | test | score | stddev_results | +---------+--------+-------+----------------+ | Chun | SQL | 75 | 16.9466 | | Chun | Tuning | 73 | 24.1247 | | Esben | SQL | 43 | 16.9466 | | Esben | Tuning | 31 | 24.1247 | | Kaolin | SQL | 56 | 16.9466 | | Kaolin | Tuning | 88 | 24.1247 | | Tatiana | SQL | 87 | 16.9466 | +---------+--------+-------+----------------+ URL: https://mariadb.com/kb/en/stddev_pop/https://mariadb.com/kb/en/stddev_pop/;5OPENSyntax ------ URL: https://mariadb.com/kb/en/open/https://mariadb.com/kb/en/open/>!RETURNSyntax ------ RETURN expr The RETURN statement terminates execution of a stored function and returns the value expr to the function caller. There must be at least one RETURN statement in a stored function. If the function has multiple exit points, all exit points must have a RETURN. This statement is not used in stored procedures, triggers, or events. LEAVE can be used instead. The following example shows that RETURN can return the result of a scalar subquery: CREATE FUNCTION users_count() RETURNS BOOL READS SQL DATA BEGIN RETURN (SELECT COUNT(DISTINCT User) FROM mysql.user); END; URL: https://mariadb.com/kb/en/return/https://mariadb.com/kb/en/return/A WHILESyntax ------ [begin_label:] WHILE search_condition DO statement_list END WHILE [end_label] Description ----------- The statement list within a WHILE statement is repeated as long as the search_condition is true. statement_list consists of one or more statements. If the loop must be executed at least once, REPEAT ... LOOP can be used instead. A WHILE statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same. Examples -------- CREATE PROCEDURE dowhile() BEGIN DECLARE v1 INT DEFAULT 5; WHILE v1 > 0 DO ... SET v1 = v1 - 1; END WHILE; END URL: https://mariadb.com/kb/en/while/https://mariadb.com/kb/en/while/4mfK ur SUMSyntax ------ SUM([DISTINCT] expr) Description ----------- Returns the sum of expr. If the return set has no rows, SUM() returns NULL. The DISTINCT keyword can be used to sum only the distinct values of expr. From MariaDB 10.2.0, SUM() can be used as a window function, although not with the DISTINCT specifier. Examples -------- CREATE TABLE sales (sales_value INT); INSERT INTO sales VALUES(10),(20),(20),(40); SELECT SUM(sales_value) FROM sales; +------------------+ | SUM(sales_value) | +------------------+ | 90 | +------------------+ SELECT SUM(DISTINCT(sales_value)) FROM sales; +----------------------------+ | SUM(DISTINCT(sales_value)) | +----------------------------+ | 70 | +----------------------------+ Commonly, SUM is used with a GROUP BY clause: CREATE TABLE sales (name CHAR(10), month CHAR(10), units INT); INSERT INTO sales VALUES ('Chun', 'Jan', 75), ('Chun', 'Feb', 73), ('Esben', 'Jan', 43), ('Esben', 'Feb', 31), ('Kaolin', 'Jan', 56), ('Kaolin', 'Feb', 88), ('Tatiana', 'Jan', 87), ('Tatiana', 'Feb', 83); SELECT name, SUM(units) FROM sales GROUP BY name; +---------+------------+ | name | SUM(units) | +---------+------------+ | Chun | 148 | | Esben | 74 | | Kaolin | 144 | | Tatiana | 170 | +---------+------------+ The GROUP BY clause is required when using an aggregate function along with regular column data, otherwise the result will be a mismatch, as in the following common type of mistake: SELECT name,SUM(units) FROM sales ; +------+------------+ | name | SUM(units) | +------+------------+ | Chun | 536 | +------+------------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, SUM(score) OVER (PARTITION BY name) AS total_score FROM student_test; +---------+--------+-------+-------------+ | name | test | score | total_score | +---------+--------+-------+-------------+ | Chun | SQL | 75 | 148 | | Chun | Tuning | 73 | 148 | | Esben | SQL | 43 | 74 | | Esben | Tuning | 31 | 74 | | Kaolin | SQL | 56 | 144 | | Kaolin | Tuning | 88 | 144 | | Tatiana | SQL | 87 | 87 | +---------+--------+-------+-------------+ URL: https://mariadb.com/kb/en/sum/https://mariadb.com/kb/en/sum/[ #VARIANCESyntax ------ VARIANCE(expr) Description ----------- Returns the population standard variance of expr. This is an extension to standard SQL. The standard SQL function VAR_POP() can be used instead. Variance is calculated by working out the mean for the set for each number, subtracting the mean and squaring the result calculate the average of the resulting differences It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, VARIANCE() can be used as a window function. VARIANCE() returns NULL if there were no matching rows. Examples -------- CREATE TABLE v(i tinyint); INSERT INTO v VALUES(101),(99); SELECT VARIANCE(i) FROM v; +-------------+ | VARIANCE(i) | +-------------+ | 1.0000 | +-------------+ INSERT INTO v VALUES(120),(80); SELECT VARIANCE(i) FROM v; +-------------+ | VARIANCE(i) | +-------------+ | 200.5000 | +-------------+ As an aggregate function: CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT); INSERT INTO stats VALUES ('a',1),('a',2),('a',3), ('b',11),('b',12),('b',20),('b',30),('b',60); SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) FROM stats GROUP BY category; +----------+---------------+----------------+------------+ | category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) | +----------+---------------+----------------+------------+ | a | 0.8165 | 1.0000 | 0.6667 | | b | 18.0400 | 20.1693 | 325.4400 | +----------+---------------+----------------+------------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, VAR_POP(score) OVER (PARTITION BY test) AS variance_results FROM student_test; +---------+--------+-------+------------------+ | name | test | score | variance_results | +---------+--------+-------+------------------+ | Chun | SQL | 75 | 287.1875 | | Chun | Tuning | 73 | 582.0000 | | Esben | SQL | 43 | 287.1875 | | Esben | Tuning | 31 | 582.0000 | | Kaolin | SQL | 56 | 287.1875 | | Kaolin | Tuning | 88 | 582.0000 | | Tatiana | SQL | 87 | 287.1875 | +---------+--------+-------+------------------+ URL: https://mariadb.com/kb/en/variance/https://mariadb.com/kb/en/variance/BQ!BUFFERA synonym for ST_BUFFER. URL: https://mariadb.com/kb/en/buffer/https://mariadb.com/kb/en/buffer/C Y%CONVEXHULLA synonym for ST_CONVEXHULL. URL: https://mariadb.com/kb/en/convexhull/https://mariadb.com/kb/en/convexhull/D-GEOMETRYCOLLECTIONSyntax ------ GeometryCollection(g1,g2,...) Description ----------- Constructs a WKB GeometryCollection. If any argument is not a well-formed WKB representation of a geometry, the return value is NULL. Examples -------- CREATE TABLE gis_geometrycollection (g GEOMETRYCOLLECTION); SHOW FIELDS FROM gis_geometrycollection; INSERT INTO gis_geometrycollection VALUES (GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0,10 10))')), (GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6), LineString(Point(3, 6), Point(7, 9)))))), (GeomFromText('GeometryCollection()')), (GeomFromText('GeometryCollection EMPTY')); URL: https://mariadb.com/kb/en/geometrycollection/https://mariadb.com/kb/en/geometrycollection/F*MULTILINESTRINGSyntax ------ MultiLineString(ls1,ls2,...) Description ----------- Constructs a WKB MultiLineString value using WKB LineString arguments. If any argument is not a WKB LineString, the return value is NULL. Example CREATE TABLE gis_multi_line (g MULTILINESTRING); INSERT INTO gis_multi_line VALUES (MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')), (MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')), (MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2), Point(3, 5)), LineString(Point(2, 5),Point(5, 8),Point(21, 7)))))); URL: https://mariadb.com/kb/en/multilinestring/https://mariadb.com/kb/en/multilinestring/G p%MULTIPOINTSyntax ------ MultiPoint(pt1,pt2,...) Description ----------- Constructs a WKB MultiPoint value using WKB Point arguments. If any argument is not a WKB Point, the return value is NULL. Examples -------- SET @g = ST_GEOMFROMTEXT('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9 3, 8 4, 6 6, 6 9, 4 9, 1 5 )'); CREATE TABLE gis_multi_point (g MULTIPOINT); INSERT INTO gis_multi_point VALUES (MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20 20)')), (MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')), (MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4, 10))))); URL: https://mariadb.com/kb/en/multipoint/https://mariadb.com/kb/en/multipoint/1i] A b "VAR_POPSyntax ------ VAR_POP(expr) Description ----------- Returns the population standard variance of expr. It considers rows as the whole population, not as a sample, so it has the number of rows as the denominator. You can also use VARIANCE(), which is equivalent but is not standard SQL. Variance is calculated by working out the mean for the set for each number, subtracting the mean and squaring the result calculate the average of the resulting differences It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, VAR_POP() can be used as a window function. VAR_POP() returns NULL if there were no matching rows. Examples -------- CREATE TABLE v(i tinyint); INSERT INTO v VALUES(101),(99); SELECT VAR_POP(i) FROM v; +------------+ | VAR_POP(i) | +------------+ | 1.0000 | +------------+ INSERT INTO v VALUES(120),(80); SELECT VAR_POP(i) FROM v; +------------+ | VAR_POP(i) | +------------+ | 200.5000 | +------------+ As an aggregate function: CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT); INSERT INTO stats VALUES ('a',1),('a',2),('a',3), ('b',11),('b',12),('b',20),('b',30),('b',60); SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) FROM stats GROUP BY category; +----------+---------------+----------------+------------+ | category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) | +----------+---------------+----------------+------------+ | a | 0.8165 | 1.0000 | 0.6667 | | b | 18.0400 | 20.1693 | 325.4400 | +----------+---------------+----------------+------------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, VAR_POP(score) OVER (PARTITION BY test) AS variance_results FROM student_test; +---------+--------+-------+------------------+ | name | test | score | variance_results | +---------+--------+-------+------------------+ | Chun | SQL | 75 | 287.1875 | | Chun | Tuning | 73 | 582.0000 | | Esben | SQL | 43 | 287.1875 | | Esben | Tuning | 31 | 582.0000 | | Kaolin | SQL | 56 | 287.1875 | | Kaolin | Tuning | 88 | 582.0000 | | Tatiana | SQL | 87 | 287.1875 | +---------+--------+-------+------------------+ URL: https://mariadb.com/kb/en/var_pop/https://mariadb.com/kb/en/var_pop/D#VAR_SAMPSyntax ------ VAR_SAMP(expr) Description ----------- Returns the sample variance of expr. That is, the denominator is the number of rows minus one. It is an aggregate function, and so can be used with the GROUP BY clause. From MariaDB 10.2.2, VAR_SAMP() can be used as a window function. VAR_SAMP() returns NULL if there were no matching rows. Examples -------- As an aggregate function: CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT); INSERT INTO stats VALUES ('a',1),('a',2),('a',3), ('b',11),('b',12),('b',20),('b',30),('b',60); SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) FROM stats GROUP BY category; +----------+---------------+----------------+------------+ | category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) | +----------+---------------+----------------+------------+ | a | 0.8165 | 1.0000 | 0.6667 | | b | 18.0400 | 20.1693 | 325.4400 | +----------+---------------+----------------+------------+ As a window function: CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, VAR_SAMP(score) OVER (PARTITION BY test) AS variance_results FROM student_test; +---------+--------+-------+------------------+ | name | test | score | variance_results | +---------+--------+-------+------------------+ | Chun | SQL | 75 | 382.9167 | | Chun | Tuning | 73 | 873.0000 | | Esben | SQL | 43 | 382.9167 | | Esben | Tuning | 31 | 873.0000 | | Kaolin | SQL | 56 | 382.9167 | | Kaolin | Tuning | 88 | 873.0000 | | Tatiana | SQL | 87 | 382.9167 | +---------+--------+-------+------------------+ URL: https://mariadb.com/kb/en/var_samp/https://mariadb.com/kb/en/var_samp/"CHARSETSyntax ------ CHARSET(str) Description ----------- Returns the character set of the string argument. If str is not a string, it is considered as a binary string (so the function returns 'binary'). This applies to NULL, too. The return value is a string in the utf8 character set. Examples -------- SELECT CHARSET('abc'); +----------------+ | CHARSET('abc') | +----------------+ | latin1 | +----------------+ SELECT CHARSET(CONVERT('abc' USING utf8)); +------------------------------------+ | CHARSET(CONVERT('abc' USING utf8)) | +------------------------------------+ | utf8 | +------------------------------------+ SELECT CHARSET(USER()); +-----------------+ | CHARSET(USER()) | +-----------------+ | utf8 | +-----------------+ URL: https://mariadb.com/kb/en/charset/https://mariadb.com/kb/en/charset/H 'MULTIPOLYGONSyntax ------ MultiPolygon(poly1,poly2,...) Description ----------- Constructs a WKB MultiPolygon value from a set of WKB Polygon arguments. If any argument is not a WKB Polygon, the return value is NULL. Example CREATE TABLE gis_multi_polygon (g MULTIPOLYGON); INSERT INTO gis_multi_polygon VALUES (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')), (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')), (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3))))))); URL: https://mariadb.com/kb/en/multipolygon/https://mariadb.com/kb/en/multipolygon/I POINTSyntax ------ Point(x,y) Description ----------- Constructs a WKB Point using the given coordinates. Examples -------- SET @g = ST_GEOMFROMTEXT('Point(1 1)'); CREATE TABLE gis_point (g POINT); INSERT INTO gis_point VALUES (PointFromText('POINT(10 10)')), (PointFromText('POINT(20 10)')), (PointFromText('POINT(20 20)')), (PointFromWKB(AsWKB(PointFromText('POINT(10 20)')))); URL: https://mariadb.com/kb/en/point/https://mariadb.com/kb/en/point/Ja)PointOnSurfaceA synonym for ST_PointOnSurface. URL: https://mariadb.com/kb/en/pointonsurface/https://mariadb.com/kb/en/pointonsurface/N#*ST_INTERSECTIONSyntax ------ ST_INTERSECTION(g1,g2) Description ----------- Returns a geometry that is the intersection, or shared portion, of geometry g1 and geometry g2. Examples -------- SET @g1 = ST_GEOMFROMTEXT('POINT(2 1)'); SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 1, 0 2)'); SELECT ASTEXT(ST_INTERSECTION(@g1,@g2)); +----------------------------------+ | ASTEXT(ST_INTERSECTION(@g1,@g2)) | +----------------------------------+ | POINT(2 1) | +----------------------------------+ URL: https://mariadb.com/kb/en/st_intersection/https://mariadb.com/kb/en/st_intersection/zj.dT } $ω F 'COERCIBILITYSyntax ------ COERCIBILITY(str) Description ----------- Returns the collation coercibility value of the string argument. Coercibility defines what will be converted to what in case of collation conflict, with an expression with higher coercibility being converted to the collation of an expression with lower coercibility. Coercibility | Description | Example | 0 | Explicit | Value using a COLLATE clause | 1 | No collation | Concatenated strings using different collations | 2 | Implicit | Column value | 3 | Constant | USER() return value | 4 | Coercible | Literal string | 5 | Ignorable | NULL or derived from NULL | Examples -------- SELECT COERCIBILITY('abc' COLLATE latin1_swedish_ci); +-----------------------------------------------+ | COERCIBILITY('abc' COLLATE latin1_swedish_ci) | +-----------------------------------------------+ | 0 | +-----------------------------------------------+ SELECT COERCIBILITY(USER()); +----------------------+ | COERCIBILITY(USER()) | +----------------------+ | 3 | +----------------------+ SELECT COERCIBILITY('abc'); +---------------------+ | COERCIBILITY('abc') | +---------------------+ | 4 | +---------------------+ URL: https://mariadb.com/kb/en/coercibility/https://mariadb.com/kb/en/coercibility/ Z'CURRENT_ROLERoles were introduced in MariaDB 10.0.5. Syntax ------ CURRENT_ROLE, CURRENT_ROLE() Description ----------- Returns the current role name. This determines your access privileges. The return value is a string in the utf8 character set. If there is no current role, NULL is returned. The output of SELECT CURRENT_ROLE is equivalent to the contents of the ENABLED_ROLES Information Schema table. USER() returns the combination of user and host used to login. CURRENT_USER() returns the account used to determine current connection's privileges. Examples -------- SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | NULL | +--------------+ SET ROLE staff; SELECT CURRENT_ROLE; +--------------+ | CURRENT_ROLE | +--------------+ | staff | +--------------+ URL: https://mariadb.com/kb/en/current_role/https://mariadb.com/kb/en/current_role/ r'CURRENT_USERSyntax ------ CURRENT_USER, CURRENT_USER() Description ----------- Returns the user name and host name combination for the MariaDB account that the server used to authenticate the current client. This account determines your access privileges. The return value is a string in the utf8 character set. The value of CURRENT_USER() can differ from the value of USER(). CURRENT_ROLE() returns the current active role. Examples -------- shell> mysql --user="anonymous" MariaDB [(none)]> select user(),current_user(); +---------------------+----------------+ | user() | current_user() | +---------------------+----------------+ | anonymous@localhost | @localhost | +---------------------+----------------+ When calling CURRENT_USER() in a stored procedure, it returns the owner of the stored procedure, as defined with DEFINER. URL: https://mariadb.com/kb/en/current_user/https://mariadb.com/kb/en/current_user/n#DATABASESyntax ------ DATABASE() Description ----------- Returns the default (current) database name as a string in the utf8 character set. If there is no default database, DATABASE() returns NULL. Within a stored routine, the default database is the database that the routine is associated with, which is not necessarily the same as the database that is the default in the calling context. SCHEMA() is a synonym for DATABASE(). To select a default database, the USE statement can be run. Another way to set the default database is specifying its name at mysql command line client startup. Examples -------- SELECT DATABASE(); +------------+ | DATABASE() | +------------+ | NULL | +------------+ USE test; Database changed SELECT DATABASE(); +------------+ | DATABASE() | +------------+ | test | +------------+ URL: https://mariadb.com/kb/en/database/https://mariadb.com/kb/en/database/"DEFAULTSyntax ------ DEFAULT(col_name) Description ----------- Returns the default value for a table column. If the column has no default value, NULL is returned. For integer columns using AUTO_INCREMENT, 0 is returned. When using DEFAULT as a value to set in an INSERT or UPDATE statement, you can use the bare keyword DEFAULT without the parentheses and argument to refer to the column in context. You can only use DEFAULT as a bare keyword if you are using it alone without a surrounding expression or function. Examples -------- Select only non-default values for a column: SELECT i FROM t WHERE i != DEFAULT(i); Update values to be one greater than the default value: UPDATE t SET i = DEFAULT(i)+1 WHERE i URL: https://mariadb.com/kb/en/default/https://mariadb.com/kb/en/default/Oa,ST_POINTONSURFACEST_POINTONSURFACE() was introduced in MariaDB 10.1.2 Syntax ------ ST_PointOnSurface(g) PointOnSurface(g) Description ----------- Given a geometry, returns a POINT guaranteed to intersect a surface. However, see MDEV-7514. ST_PointOnSurface() and PointOnSurface() are synonyms. URL: https://mariadb.com/kb/en/st_pointonsurface/https://mariadb.com/kb/en/st_pointonsurface/T!BINLOGSyntax ------ BINLOG 'str' Description ----------- BINLOG is an internal-use statement. It is generated by the mysqlbinlog program as the printable representation of certain events in binary log files. The 'str' value is a base 64-encoded string the that server decodes to determine the data change indicated by the corresponding event. This statement requires the SUPER privilege. It was added in MySQL 5.1.5. URL: https://mariadb.com/kb/en/binlog/https://mariadb.com/kb/en/binlog/Q@ V FLUSHWy,FLUSH QUERY CACHEDescription ----------- You can defragment the query cache to better utilize its memory with the FLUSH QUERY CACHE statement. The statement does not remove any queries from the cache. The RESET QUERY CACHE statement removes all query results from the query cache. The FLUSH TABLES statement also does this. URL: https://mariadb.com/kb/en/flush-query-cache/https://mariadb.com/kb/en/flush-query-cache/[ %LOAD INDEXSyntax ------ LOAD INDEX INTO CACHE tbl_index_list [, tbl_index_list] ... tbl_index_list: tbl_name [[INDEX|KEY] (index_name[, index_name] ...)] [IGNORE LEAVES] Description ----------- The LOAD INDEX INTO CACHE statement preloads a table index into the key cache to which it has been assigned by an explicit CACHE INDEX statement, or into the default key cache otherwise. LOAD INDEX INTO CACHE is used only for MyISAM or Aria tables. Until MariaDB 5.3, it was not supported for tables having user-defined partitioning, but this limitation was removed in MariaDB 5.5. The IGNORE LEAVES modifier causes only blocks for the nonleaf nodes of the index to be preloaded. URL: https://mariadb.com/kb/en/load-index/https://mariadb.com/kb/en/load-index/y--SHOW FUNCTION CODESyntax ------ SHOW FUNCTION CODE func_name Description ----------- SHOW FUNCTION CODE shows a representation of the internal implementation of the stored function. It is similar to SHOW PROCEDURE CODE but for stored functions. URL: https://mariadb.com/kb/en/show-function-code/https://mariadb.com/kb/en/show-function-code/z.)[,/ 7 +~\k/+DECODE_HISTOGRAMDECODE_HISTOGRAM() was introduced in MariaDB 10.0.2 Syntax ------ DECODE_HISTOGRAM(hist_type,histogram) Note: Before MariaDB 10.0.10 the arguments were reversed. Description ----------- Returns a string of comma separated numeric values corresponding to a probability distribution represented by the histogram of type hist_type (SINGLE_PREC_HB or DOUBLE_PREC_HB). The hist_type and histogram would be commonly used from the mysql.column_stats table. See Histogram Based Statistics for details. Examples -------- CREATE TABLE origin ( i INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, v INT UNSIGNED NOT NULL ); INSERT INTO origin(v) VALUES (1),(2),(3),(4),(5),(10),(20), (30),(40),(50),(60),(70),(80), (90),(100),(200),(400),(800); SET histogram_size=10,histogram_type=SINGLE_PREC_HB; ANALYZE TABLE origin PERSISTENT FOR ALL; +-------------+---------+----------+-----------------------------------------+ | Table | Op | Msg_type | Msg_text | +-------------+---------+----------+-----------------------------------------+ | test.origin | analyze | status | Engine-independent statistics collected | | test.origin | analyze | status | OK | +-------------+---------+----------+-----------------------------------------+ SELECT db_name,table_name,column_name,hist_type, hex(histogram),decode_histogram(hist_type,histogram) FROM mysql.column_stats WHERE db_name='test' and table_name='origin'; +---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+ | db_name | table_name | column_name | hist_type | hex(histogram) | decode_histogram(hist_type,histogram) | +---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+ | test | origin | i | SINGLE_PREC_HB | 0F2D3C5A7887A5C3D2F0 | 0.059,0.118,0.059,0.118,0.118,0.059,0.118,0.118,0.059,0.118,0.059 | | test | origin | v | SINGLE_PREC_HB | 000001060C0F161C1F7F | 0.000,0.000,0.004,0.020,0.024,0.012,0.027,0.024,0.012,0.376,0.502 | +---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+ SET histogram_size=20,histogram_type=DOUBLE_PREC_HB; ANALYZE TABLE origin PERSISTENT FOR ALL; +-------------+---------+----------+-----------------------------------------+ | Table | Op | Msg_type | Msg_text | +-------------+---------+----------+-----------------------------------------+ | test.origin | analyze | status | Engine-independent statistics collected | | test.origin | analyze | status | OK | +-------------+---------+----------+-----------------------------------------+ SELECT db_name,table_name,column_name, hist_type,hex(histogram),decode_histogram(hist_type,histogram) FROM mysql.column_stats WHERE db_name='test' and table_name='origin'; +---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+ | db_name | table_name | column_name | hist_type | hex(histogram) | decode_histogram(hist_type,histogram) | +---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+ | test | origin | i | DOUBLE_PREC_HB | 0F0F2D2D3C3C5A5A78788787A5A5C3C3D2D2F0F0 | 0.05882,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.05882 | | test | origin | v | DOUBLE_PREC_HB | 5200F600480116067E0CB30F1B16831CB81FD67F | 0.00125,0.00250,0.00125,0.01877,0.02502,0.01253,0.02502,0.02502,0.01253,0.37546,0.50063 | URL: https://mariadb.com/kb/en/decode_histogram/https://mariadb.com/kb/en/decode_histogram/ %FOUND_ROWSSyntax ------ FOUND_ROWS() Description ----------- A SELECT statement may include a LIMIT clause to restrict the number of rows the server returns to the client. In some cases, it is desirable to know how many rows the statement would have returned without the LIMIT, but without running the statement again. To obtain this row count, include a SQL_CALC_FOUND_ROWS option in the SELECT statement, and then invoke FOUND_ROWS() afterwards. You can also use FOUND_ROWS() to obtain the number of rows returned by a SELECT which does not contain a LIMIT clause. In this case you don't need to use the SQL_CALC_FOUND_ROWS option. This can be useful for example in a stored procedure. Also, this function works with some other statements which return a resultset, including SHOW, DESC and HELP. For DELETE ... RETURNING you should use ROW_COUNT(). It also works as a prepared statement, or after executing a prepared statement. Statements which don't return any results don't affect FOUND_ROWS() - the previous value will still be returned. Warning: When used after a CALL statement, this function returns the number of rows selected by the last query in the procedure, not by the whole procedure. Statements using the FOUND_ROWS() function are not safe for replication. Examples -------- SHOW ENGINES; +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | Engine | Support | Comment | Transactions | XA | Savepoints | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES | ... | SPHINX | YES | Sphinx storage engine | NO | NO | NO | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ 11 rows in set (0.01 sec) SELECT FOUND_ROWS(); +--------------+ | FOUND_ROWS() | +--------------+ | 11 | +--------------+ SELECT SQL_CALC_FOUND_ROWS * FROM tbl_name WHERE id > 100 LIMIT 10; SELECT FOUND_ROWS(); +--------------+ | FOUND_ROWS() | +--------------+ | 23 | +--------------+ URL: https://mariadb.com/kb/en/found_rows/https://mariadb.com/kb/en/found_rows/ :(SHOW PROFILESSyntax ------ SHOW PROFILES Description ----------- The SHOW PROFILES statement displays profiling information that indicates resource usage for statements executed during the course of the current session. It is used together with SHOW PROFILE. URL: https://mariadb.com/kb/en/show-profiles/https://mariadb.com/kb/en/show-profiles/`3SHOW QUERY_RESPONSE_TIMESHOW QUERY_RESPONSE_TIME was introduced in MariaDB 10.1.1. Starting with MariaDB 10.1.1, which introduced the Information Schema plugin extension, it is possible to use SHOW QUERY_RESPONSE_TIME as an alternative for retrieving information from the QUERY_RESPONSE_TIME plugin. URL: https://mariadb.com/kb/en/show-query_response_time/https://mariadb.com/kb/en/show-query_response_time/d@e K.,SHOW SLAVE STATUSf@  E&SHOW STATUSDOSyntax ------ DO expr [, expr] ... Description ----------- DO executes the expressions but does not return any results. In most respects, DO is shorthand for SELECT expr, ..., but has the advantage that it is slightly faster when you do not care about the result. DO is useful primarily with functions that have side effects, such as RELEASE_LOCK(). URL: https://mariadb.com/kb/en/do/https://mariadb.com/kb/en/do//5N}-! !lN+)LAST_INSERT_IDSyntax ------ LAST_INSERT_ID(), LAST_INSERT_ID(expr) Description ----------- LAST_INSERT_ID() (no arguments) returns the first automatically generated value successfully inserted for an AUTO_INCREMENT column as a result of the most recently executed INSERT statement. The value of LAST_INSERT_ID() remains unchanged if no rows are successfully inserted. If one gives an argument to LAST_INSERT_ID(), then it will return the value of the expression and the next call to LAST_INSERT_ID() will return the same value. The value will also be sent to the client and can be accessed by the mysql_insert_id function. For example, after inserting a row that generates an AUTO_INCREMENT value, you can get the value like this: SELECT LAST_INSERT_ID(); +------------------+ | LAST_INSERT_ID() | +------------------+ | 9 | +------------------+ You can also use LAST_INSERT_ID() to delete the last inserted row: DELETE FROM product WHERE id = LAST_INSERT_ID(); If no rows were successfully inserted, LAST_INSERT_ID() returns 0. The value of LAST_INSERT_ID() will be consistent across all versions if all rows in the INSERT or UPDATE statement were successful. The currently executing statement does not affect the value of LAST_INSERT_ID(). Suppose that you generate an AUTO_INCREMENT value with one statement, and then refer to LAST_INSERT_ID() in a multiple-row INSERT statement that inserts rows into a table with its own AUTO_INCREMENT column. The value of LAST_INSERT_ID() will remain stable in the second statement; its value for the second and later rows is not affected by the earlier row insertions. (However, if you mix references to LAST_INSERT_ID() and LAST_INSERT_ID(expr), the effect is undefined.) If the previous statement returned an error, the value of LAST_INSERT_ID() is undefined. For transactional tables, if the statement is rolled back due to an error, the value of LAST_INSERT_ID() is left undefined. For manual ROLLBACK, the value of LAST_INSERT_ID() is not restored to that before the transaction; it remains as it was at the point of the ROLLBACK. Within the body of a stored routine (procedure or function) or a trigger, the value of LAST_INSERT_ID() changes the same way as for statements executed outside the body of these kinds of objects. The effect of a stored routine or trigger upon the value of LAST_INSERT_ID() that is seen by following statements depends on the kind of routine: If a stored procedure executes statements that change the value of LAST_INSERT_ID(), the new value will be seen by statements that follow the procedure call. For stored functions and triggers that change the value, the value is restored when the function or trigger ends, so following statements will not see a changed value. Examples -------- CREATE TABLE t ( id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY, f VARCHAR(1)) ENGINE = InnoDB; INSERT INTO t(f) VALUES('a'); SELECT LAST_INSERT_ID(); +------------------+ | LAST_INSERT_ID() | +------------------+ | 1 | +------------------+ INSERT INTO t(f) VALUES('b'); INSERT INTO t(f) VALUES('c'); SELECT LAST_INSERT_ID(); +------------------+ | LAST_INSERT_ID() | +------------------+ | 3 | +------------------+ INSERT INTO t(f) VALUES('d'),('e'); SELECT LAST_INSERT_ID(); +------------------+ | LAST_INSERT_ID() | +------------------+ | 4 | +------------------+ SELECT * FROM t; +----+------+ | id | f | +----+------+ | 1 | a | | 2 | b | | 3 | c | | 4 | d | | 5 | e | +----+------+ SELECT LAST_INSERT_ID(12); +--------------------+ | LAST_INSERT_ID(12) | +--------------------+ | 12 | +--------------------+ SELECT LAST_INSERT_ID(); +------------------+ | LAST_INSERT_ID() | +------------------+ | 12 | +------------------+ INSERT INTO t(f) VALUES('f'); SELECT LAST_INSERT_ID(); +------------------+ | LAST_INSERT_ID() | +------------------+ | 6 | +------------------+ SELECT * FROM t; +----+------+ | id | f | +----+------+ | 1 | a | | 2 | b | | 3 | c | | 4 | d | | 5 | e | | 6 | f | +----+------+ SELECT LAST_INSERT_ID(12); +--------------------+ | LAST_INSERT_ID(12) | +--------------------+ | 12 | +--------------------+ INSERT INTO t(f) VALUES('g'); SELECT * FROM t; +----+------+ | id | f | +----+------+ | 1 | a | | 2 | b | | 3 | c | | 4 | d | | 5 | e | | 6 | f | | 7 | g | +----+------+ URL: https://mariadb.com/kb/en/last_insert_id/https://mariadb.com/kb/en/last_insert_id/d,PROCEDURE ANALYSESyntax ------ analyse([max_elements[,max_memory]]) Description ----------- This procedure is defined in the sql/sql_analyse.cc file. It examines the result from a query and returns an analysis of the results that suggests optimal data types for each column. To obtain this analysis, append PROCEDURE ANALYSE to the end of a SELECT statement: SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max_elements,[max_memory]]) For example: SELECT col1, col2 FROM table1 PROCEDURE ANALYSE(10, 2000); The results show some statistics for the values returned by the query, and propose an optimal data type for the columns. This can be helpful for checking your existing tables, or after importing new data. You may need to try different settings for the arguments so that PROCEDURE ANALYSE() does not suggest the ENUM data type when it is not appropriate. The arguments are optional and are used as follows: max_elements (default 256) is the maximum number of distinct values that analyse notices per column. This is used by analyse to check whether the optimal data type should be of type ENUM; if there are more than max_elements distinct values, then ENUM is not a suggested type. max_memory (default 8192) is the maximum amount of memory that analyse should allocate per column while trying to find all distinct values. URL: https://mariadb.com/kb/en/procedure-analyse/https://mariadb.com/kb/en/procedure-analyse/DUALDescription ----------- You are allowed to specify DUAL as a dummy table name in situations where no tables are referenced, such as the following SELECT statement: SELECT 1 + 1 FROM DUAL; +-------+ | 1 + 1 | +-------+ | 2 | +-------+ DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses. MariaDB ignores the clauses. MariaDB does not require FROM DUAL if no tables are referenced. FROM DUAL could be used when you only SELECT computed values, but require a WHERE clause, perhaps to test that a script correctly handles empty resultsets: SELECT 1 FROM DUAL WHERE FALSE; Empty set (0.00 sec) URL: https://mariadb.com/kb/en/dual/https://mariadb.com/kb/en/dual/ n%FOR UPDATEThe FOR UPDATE clause of SELECT applies only when autocommit is set to 0 or the SELECT is enclosed in a transaction. A lock is acquired on the rows, and other transactions are prevented from writing the rows, acquire locks, and from reading them (unless their isolation level is READ UNCOMMITTED). If autocommit is set to 1, the LOCK IN SHARE MODE and FOR UPDATE clauses have no effect. If the isolation level is set to SERIALIZABLE, all plain SELECT statements are converted to SELECT ... LOCK IN SHARE MODE. Example SELECT * FROM trans WHERE period=2001 FOR UPDATE; URL: https://mariadb.com/kb/en/for-update/https://mariadb.com/kb/en/for-update/c Wc, %LAST_VALUESyntax ------ LAST_VALUE(expr,[expr,...]) LAST_VALUE(expr) OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- LAST_VALUE() evaluates all expressions and returns the last. This is useful together with setting user variables to a value with @var:=expr, for example when you want to get data of rows updated/deleted without having to do two queries against the table. Since MariaDB 10.2.2, LAST_VALUE can be used as a window function. Returns NULL if no last value exists. Examples -------- CREATE TABLE t1 (a int, b int); INSERT INTO t1 VALUES(1,10),(2,20); DELETE FROM t1 WHERE a=1 AND last_value(@a:=a,@b:=b,1); SELECT @a,@b; +------+------+ | @a | @b | +------+------+ | 1 | 10 | +------+------+ As a window function: CREATE TABLE t1 ( pk int primary key, a int, b int, c char(10), d decimal(10, 3), e real ); INSERT INTO t1 VALUES ( 1, 0, 1, 'one', 0.1, 0.001), ( 2, 0, 2, 'two', 0.2, 0.002), ( 3, 0, 3, 'three', 0.3, 0.003), ( 4, 1, 2, 'three', 0.4, 0.004), ( 5, 1, 1, 'two', 0.5, 0.005), ( 6, 1, 1, 'one', 0.6, 0.006), ( 7, 2, NULL, 'n_one', 0.5, 0.007), ( 8, 2, 1, 'n_two', NULL, 0.008), ( 9, 2, 2, NULL, 0.7, 0.009), (10, 2, 0, 'n_four', 0.8, 0.010), (11, 2, 10, NULL, 0.9, NULL); SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc, LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc, FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc, LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc FROM t1 ORDER BY pk DESC; +----+-----------+----------+------------+-----------+ | pk | first_asc | last_asc | first_desc | last_desc | +----+-----------+----------+------------+-----------+ | 11 | 1 | 11 | 11 | 11 | | 10 | 1 | 10 | 11 | 10 | | 9 | 1 | 9 | 11 | 9 | | 8 | 1 | 8 | 11 | 8 | | 7 | 1 | 7 | 11 | 7 | | 6 | 1 | 6 | 11 | 6 | | 5 | 1 | 5 | 11 | 5 | | 4 | 1 | 4 | 11 | 4 | | 3 | 1 | 3 | 11 | 3 | | 2 | 1 | 2 | 11 | 2 | | 1 | 1 | 1 | 11 | 1 | +----+-----------+----------+------------+-----------+ CREATE OR REPLACE TABLE t1 (i int); INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10); SELECT i, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS f_1f, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS l_1f, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f FROM t1; +------+------+------+--------+--------+--------+--------+--------+--------+ | i | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p | f_1f2f | f_1f2f | +------+------+------+--------+--------+--------+--------+--------+--------+ | 1 | 1 | 2 | 1 | 2 | NULL | NULL | 2 | 3 | | 2 | 2 | 3 | 1 | 3 | 1 | 1 | 3 | 4 | | 3 | 3 | 4 | 2 | 4 | 1 | 2 | 4 | 5 | | 4 | 4 | 5 | 3 | 5 | 2 | 3 | 5 | 6 | | 5 | 5 | 6 | 4 | 6 | 3 | 4 | 6 | 7 | | 6 | 6 | 7 | 5 | 7 | 4 | 5 | 7 | 8 | | 7 | 7 | 8 | 6 | 8 | 5 | 6 | 8 | 9 | | 8 | 8 | 9 | 7 | 9 | 6 | 7 | 9 | 10 | | 9 | 9 | 10 | 8 | 10 | 7 | 8 | 10 | 10 | | 10 | 10 | 10 | 9 | 10 | 8 | 9 | NULL | NULL | +------+------+------+--------+--------+--------+--------+--------+--------+ URL: https://mariadb.com/kb/en/last_value/https://mariadb.com/kb/en/last_value/ $ROW_COUNTSyntax ------ ROW_COUNT() Description ----------- ROW_COUNT() returns the number of rows updated, inserted or deleted by the preceding statement. This is the same as the row count that the mysql client displays and the value from the mysql_affected_rows() C API function. Generally: For statements which return a result set (such as SELECT, SHOW, DESC or HELP), returns -1, even when the result set is empty. This is also true for administrative statements, such as OPTIMIZE. For DML statements other than SELECT and for ALTER TABLE, returns the number of affected rows. For DDL statements (including TRUNCATE) and for other statements which don't return any result set (such as USE, DO, SIGNAL or DEALLOCATE PREPARE), returns 0. For UPDATE, affected rows is by default the number of rows that were actually changed. If the CLIENT_FOUND_ROWS flag to mysql_real_connect() is specified when connecting to mysqld, affected rows is instead the number of rows matched by the WHERE clause. For REPLACE, deleted rows are also counted. So, if REPLACE deletes a row and adds a new row, ROW_COUNT() returns 2. For INSERT ... ON DUPLICATE KEY, updated rows are counted twice. So, if INSERT adds a new rows and modifies another row, ROW_COUNT() returns 3. ROW_COUNT() does not take into account rows that are not directly deleted/updated by the last statement. This means that rows deleted by foreign keys or triggers are not counted. Warning: You can use ROW_COUNT() with prepared statements, but you need to call it after EXECUTE, not after DEALLOCATE PREPARE, because the row count for allocate prepare is always 0. Warning: When used after a CALL statement, this function returns the number of rows affected by the last statement in the procedure, not by the whole procedure. Warning: After INSERT DELAYED, ROW_COUNT() returns the number of the rows you tried to insert, not the number of the successful writes. This information can also be found in the diagnostics area. Statements using the ROW_COUNT() function are not safe for replication. Examples -------- CREATE TABLE t (A INT); INSERT INTO t VALUES(1),(2),(3); SELECT ROW_COUNT(); +-------------+ | ROW_COUNT() | +-------------+ | 3 | +-------------+ DELETE FROM t WHERE A IN(1,2); SELECT ROW_COUNT(); +-------------+ | ROW_COUNT() | +-------------+ | 2 | +-------------+ Example with prepared statements: SET @q = 'INSERT INTO t VALUES(1),(2),(3);'; PREPARE stmt FROM @q; EXECUTE stmt; Query OK, 3 rows affected (0.39 sec) Records: 3 Duplicates: 0 Warnings: 0 SELECT ROW_COUNT(); +-------------+ | ROW_COUNT() | +-------------+ | 3 | +-------------+ URL: https://mariadb.com/kb/en/row_count/https://mariadb.com/kb/en/row_count/+HANDLER CommandsSyntax ------ HANDLER tbl_name OPEN [ [AS] alias] HANDLER tbl_name READ index_name { = | >= | = | URL: https://mariadb.com/kb/en/handler-commands/https://mariadb.com/kb/en/handler-commands/-LOCK IN SHARE MODEWhen LOCK IN SHARE MODE is specified in a SELECT statement, MariaDB will wait until all transactions that have modified the rows are committed. Then, a write lock is acquired. All transactions can read the rows, but if they want to modify them, they have to wait until your transaction is committed. InnoDB/XtraDB supports row-level locking. selected rows can be locked using LOCK IN SHARE MODE or FOR UPDATE. In both cases, a lock is acquired on the rows read by the query, and it will be released when the current transaction is committed. If autocommit is set to 1, the LOCK IN SHARE MODE and FOR UPDATE clauses have no effect. URL: https://mariadb.com/kb/en/lock-in-share-mode/https://mariadb.com/kb/en/lock-in-share-mode/" 2 V]USERSyntax ------ USER() Description ----------- Returns the current MariaDB user name and host name, given when authenticating to MariaDB, as a string in the utf8 character set. Note that the value of USER() may differ from the value of CURRENT_USER(), which is the user used to authenticate the current client. CURRENT_ROLE() returns the current active role. SYSTEM_USER() and SESSION_USER are synonyms for USER(). Statements using the USER() function or one of its synonyms are not safe for statement level replication. Examples -------- shell> mysql --user="anonymous" MariaDB [(none)]> select user(),current_user(); +---------------------+----------------+ | user() | current_user() | +---------------------+----------------+ | anonymous@localhost | @localhost | +---------------------+----------------+ URL: https://mariadb.com/kb/en/user/https://mariadb.com/kb/en/user/""VERSIONSyntax ------ VERSION() Description ----------- Returns a string that indicates the MariaDB server version. The string uses the utf8 character set. Examples -------- SELECT VERSION(); +----------------+ | VERSION() | +----------------+ | 10.4.7-MariaDB | +----------------+ The VERSION() string may have one or more of the following suffixes: Suffix | Description | -embedded | The server is an embedded server (libmysqld). | -log | General logging, slow logging or binary (replication) logging is enabled. | -debug | The server is compiled for debugging. | -valgrind |  The server is compiled to be instrumented with valgrind. | Changing the Version String Some old legacy code may break because they are parsing the VERSION string and expecting a MySQL string or a simple version string like Joomla til API17, see MDEV-7780. From MariaDB 10.2, one can fool these applications by setting the version string from the command line or the my.cnf files with --version=.... URL: https://mariadb.com/kb/en/version/https://mariadb.com/kb/en/version/$Not Equal OperatorSyntax ------ , != Description ----------- Not equal operator. Evaluates both SQL expressions and returns 1 if they are not equal and 0 if they are equal, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion. When used in row comparisons these two queries return the same results: SELECT (t1.a, t1.b) != (t2.x, t2.y) FROM t1 INNER JOIN t2; SELECT (t1.a != t2.x) OR (t1.b != t2.y) FROM t1 INNER JOIN t2; Examples -------- SELECT '.01' '0.01'; +-----------------+ | '.01' '0.01' | +-----------------+ | 1 | +-----------------+ SELECT .01 '0.01'; +---------------+ | .01 '0.01' | +---------------+ | 0 | +---------------+ SELECT 'zapp' 'zappp'; +-------------------+ | 'zapp' 'zappp' | +-------------------+ | 1 | +-------------------+ URL: https://mariadb.com/kb/en/not-equal/https://mariadb.com/kb/en/not-equal/ *<=>Syntax ------ Description ----------- NULL-safe equal operator. It performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL. a b is equivalent to a = b OR (a IS NULL AND b IS NULL). When used in row comparisons these two queries return the same results: SELECT (t1.a, t1.b) (t2.x, t2.y) FROM t1 INNER JOIN t2; SELECT (t1.a t2.x) AND (t1.b t2.y) FROM t1 INNER JOIN t2; See also NULL Values in MariaDB. Examples -------- SELECT 1 1, NULL NULL, 1 NULL; +---------+---------------+------------+ | 1 1 | NULL NULL | 1 NULL | +---------+---------------+------------+ | 1 | 1 | 0 | +---------+---------------+------------+ SELECT 1 = 1, NULL = NULL, 1 = NULL; +-------+-------------+----------+ | 1 = 1 | NULL = NULL | 1 = NULL | +-------+-------------+----------+ | 1 | NULL | NULL | +-------+-------------+----------+ URL: https://mariadb.com/kb/en/null-safe-equal/https://mariadb.com/kb/en/null-safe-equal/ =Syntax ------ left_expr = right_expr Description ----------- Equal operator. Evaluates both SQL expressions and returns 1 if they are equal, 0 if they are not equal, or NULL if either expression is NULL. If the expressions return different data types (for example, a number and a string), a type conversion is performed. When used in row comparisons these two queries are synonymous and return the same results: SELECT (t1.a, t1.b) = (t2.x, t2.y) FROM t1 INNER JOIN t2; SELECT (t1.a = t2.x) AND (t1.b = t2.y) FROM t1 INNER JOIN t2; To perform a NULL-safe comparison, use the operator. = can also be used as an assignment operator. Examples -------- SELECT 1 = 0; +-------+ | 1 = 0 | +-------+ | 0 | +-------+ SELECT '0' = 0; +---------+ | '0' = 0 | +---------+ | 1 | +---------+ SELECT '0.0' = 0; +-----------+ | '0.0' = 0 | +-----------+ | 1 | +-----------+ SELECT '0.01' = 0; +------------+ | '0.01' = 0 | +------------+ | 0 | +------------+ SELECT '.01' = 0.01; +--------------+ | '.01' = 0.01 | +--------------+ | 1 | +--------------+ SELECT (5 * 2) = CONCAT('1', '0'); +----------------------------+ | (5 * 2) = CONCAT('1', '0') | +----------------------------+ | 1 | +----------------------------+ SELECT 1 = NULL; +----------+ | 1 = NULL | +----------+ | NULL | +----------+ SELECT NULL = NULL; +-------------+ | NULL = NULL | +-------------+ | NULL | +-------------+ URL: https://mariadb.com/kb/en/equal/https://mariadb.com/kb/en/equal/ 4$PROCEDUREThe PROCEDURE clause of SELECT passes the whole result set to a Procedure which will process it. These Procedures are not Stored Procedures, and can only be written in the C language, so it is necessary to recompile the server. Currently, the only available procedure is ANALYSE, which examines the resultset and suggests the optimal datatypes for each column. It is defined in the sql/sql_analyse.cc file, and can be used as an example to create more Procedures. This clause cannot be used in a view's definition. URL: https://mariadb.com/kb/en/procedure/https://mariadb.com/kb/en/procedure/|@ E"EXPLAIN*EXPLAIN ANALYZEThe syntax for the EXPLAIN ANALYZE feature was changed to ANALYZE statement, available since MariaDB 10.1.0. See ANALYZE statement. URL: https://mariadb.com/kb/en/explain-analyze/https://mariadb.com/kb/en/explain-analyze/#CONTAINSSyntax ------ Contains(g1,g2) Description ----------- Returns 1 or 0 to indicate whether a geometry g1 completely contains geometry g2. CONTAINS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_CONTAINS() uses object shapes. This tests the opposite relationship to Within(). URL: https://mariadb.com/kb/en/contains/https://mariadb.com/kb/en/contains/"CROSSESSyntax ------ Crosses(g1,g2) Description ----------- Returns 1 if g1 spatially crosses g2. Returns NULL if g1 is a Polygon or a MultiPolygon, or if g2 is a Point or a MultiPoint. Otherwise, returns 0. The term spatially crosses denotes a spatial relation between two given geometries that has the following properties: The two geometries intersect Their intersection results in a geometry that has a dimension that is one less than the maximum dimension of the two given geometries Their intersection is not equal to either of the two given geometries CROSSES() is based on the original MySQL implementation, and uses object bounding rectangles, while ST_CROSSES() uses object shapes. URL: https://mariadb.com/kb/en/crosses/https://mariadb.com/kb/en/crosses/X& f+o 6Y nUS  '>Syntax ------ > Description ----------- Greater than operator. Evaluates both SQL expressions and returns 1 if the left value is greater than the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion. When used in row comparisons these two queries return the same results: SELECT (t1.a, t1.b) > (t2.x, t2.y) FROM t1 INNER JOIN t2; SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b > t2.y)) FROM t1 INNER JOIN t2; Examples -------- SELECT 2 > 2; +-------+ | 2 > 2 | +-------+ | 0 | +-------+ SELECT 'b' > 'a'; +-----------+ | 'b' > 'a' | +-----------+ | 1 | +-----------+ URL: https://mariadb.com/kb/en/greater-than/https://mariadb.com/kb/en/greater-than/70>=Syntax ------ >= Description ----------- Greater than or equal operator. Evaluates both SQL expressions and returns 1 if the left value is greater than or equal to the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion. When used in row comparisons these two queries return the same results: SELECT (t1.a, t1.b) >= (t2.x, t2.y) FROM t1 INNER JOIN t2; SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b >= t2.y)) FROM t1 INNER JOIN t2; Examples -------- SELECT 2 >= 2; +--------+ | 2 >= 2 | +--------+ | 1 | +--------+ SELECT 'A' >= 'a'; +------------+ | 'A' >= 'a' | +------------+ | 1 | +------------+ URL: https://mariadb.com/kb/en/greater-than-or-equal/https://mariadb.com/kb/en/greater-than-or-equal/#COALESCESyntax ------ COALESCE(value,...) Description ----------- Returns the first non-NULL value in the list, or NULL if there are no non-NULL values. At least one parameter must be passed. See also NULL Values in MariaDB. Examples -------- SELECT COALESCE(NULL,1); +------------------+ | COALESCE(NULL,1) | +------------------+ | 1 | +------------------+ SELECT COALESCE(NULL,NULL,NULL); +--------------------------+ | COALESCE(NULL,NULL,NULL) | +--------------------------+ | NULL | +--------------------------+ When two arguments are given, COALESCE() is the same as IFNULL(): SET @a=NULL, @b=1; SELECT COALESCE(@a, @b), IFNULL(@a, @b); +------------------+----------------+ | COALESCE(@a, @b) | IFNULL(@a, @b) | +------------------+----------------+ | 1 | 1 | +------------------+----------------+ Hex type confusion: CREATE TABLE t1 (a INT, b VARCHAR(10)); INSERT INTO t1 VALUES (0x31, 0x61),(COALESCE(0x31), COALESCE(0x61)); SELECT * FROM t1; +------+------+ | a | b | +------+------+ | 49 | a | | 1 | a | +------+------+ The reason for the differing results above is that when 0x31 is inserted directly to the column, it's treated as a number (see Hexadecimal Literals), while when 0x31 is passed to COALESCE(), it's treated as a string, because: HEX values have a string data type by default. COALESCE() has the same data type as the argument. URL: https://mariadb.com/kb/en/coalesce/https://mariadb.com/kb/en/coalesce/INSyntax ------ expr IN (value,...) Description ----------- Returns 1 if expr is equal to any of the values in the IN list, else returns 0. If all values are constants, they are evaluated according to the type of expr and sorted. The search for the item then is done using a binary search. This means IN is very quick if the IN value list consists entirely of constants. Otherwise, type conversion takes place according to the rules described at Type Conversion, but applied to all the arguments. If expr is NULL, IN always returns NULL. If at least one of the values in the list is NULL, and one of the comparisons is true, the result is 1. If at least one of the values in the list is NULL and none of the comparisons is true, the result is NULL. Examples -------- SELECT 2 IN (0,3,5,7); +----------------+ | 2 IN (0,3,5,7) | +----------------+ | 0 | +----------------+ SELECT 'wefwf' IN ('wee','wefwf','weg'); +----------------------------------+ | 'wefwf' IN ('wee','wefwf','weg') | +----------------------------------+ | 1 | +----------------------------------+ Type conversion: SELECT 1 IN ('1', '2', '3'); +----------------------+ | 1 IN ('1', '2', '3') | +----------------------+ | 1 | +----------------------+ SELECT NULL IN (1, 2, 3); +-------------------+ | NULL IN (1, 2, 3) | +-------------------+ | NULL | +-------------------+ MariaDB [(none)]> SELECT 1 IN (1, 2, NULL); +-------------------+ | 1 IN (1, 2, NULL) | +-------------------+ | 1 | +-------------------+ MariaDB [(none)]> SELECT 5 IN (1, 2, NULL); +-------------------+ | 5 IN (1, 2, NULL) | +-------------------+ | NULL | +-------------------+ URL: https://mariadb.com/kb/en/in/https://mariadb.com/kb/en/in/#DISJOINTSyntax ------ Disjoint(g1,g2) Description ----------- Returns 1 or 0 to indicate whether g1 is spatially disjoint from (does not intersect) g2. DISJOINT() tests the opposite relationship to INTERSECTS(). DISJOINT() is based on the original MySQL implementation and uses object bounding rectangles, while ST_DISJOINT() uses object shapes. URL: https://mariadb.com/kb/en/disjoint/https://mariadb.com/kb/en/disjoint/!EQUALSSyntax ------ Equals(g1,g2) From MariaDB 10.2.3: MBREQUALS(g1,g2) Description ----------- Returns 1 or 0 to indicate whether g1 is spatially equal to g2. EQUALS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_EQUALS() uses object shapes. From MariaDB 10.2.3, MBREQUALS is a synonym for Equals. URL: https://mariadb.com/kb/en/equals/https://mariadb.com/kb/en/equals/ %INTERSECTSSyntax ------ INTERSECTS(g1,g2) Description ----------- Returns 1 or 0 to indicate whether geometry g1 spatially intersects geometry g2. INTERSECTS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_INTERSECTS() uses object shapes. INTERSECTS() tests the opposite relationship to DISJOINT(). URL: https://mariadb.com/kb/en/intersects/https://mariadb.com/kb/en/intersects/#OVERLAPSSyntax ------ OVERLAPS(g1,g2) Description ----------- Returns 1 or 0 to indicate whether g1 spatially overlaps g2. The term spatially overlaps is used if two geometries intersect and their intersection results in a geometry of the same dimension but not equal to either of the given geometries. OVERLAPS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_OVERLAPS() uses object shapes. URL: https://mariadb.com/kb/en/overlaps/https://mariadb.com/kb/en/overlaps/ (ST_DIFFERENCESyntax ------ ST_DIFFERENCE(g1,g2) Description ----------- Returns a geometry representing the point set difference of the given geometry values. Example SET @g1 = POINT(10,10), @g2 = POINT(20,20); SELECT ST_AsText(ST_Difference(@g1, @g2)); +------------------------------------+ | ST_AsText(ST_Difference(@g1, @g2)) | +------------------------------------+ | POINT(10 10) | +------------------------------------+ URL: https://mariadb.com/kb/en/st_difference/https://mariadb.com/kb/en/st_difference/*&%X Qz EB+ UISSyntax ------ IS boolean_value Description ----------- Tests a value against a boolean value, where boolean_value can be TRUE, FALSE, or UNKNOWN. There is an important difference between using IS TRUE or comparing a value with TRUE using =. When using =, only 1 equals to TRUE. But when using IS TRUE, all values which are logically true (like a number > 1) return TRUE. Examples -------- SELECT 1 IS TRUE, 0 IS FALSE, NULL IS UNKNOWN; +-----------+------------+-----------------+ | 1 IS TRUE | 0 IS FALSE | NULL IS UNKNOWN | +-----------+------------+-----------------+ | 1 | 1 | 1 | +-----------+------------+-----------------+ Difference between = and IS TRUE: SELECT 2 = TRUE, 2 IS TRUE; +----------+-----------+ | 2 = TRUE | 2 IS TRUE | +----------+-----------+ | 0 | 1 | +----------+-----------+ URL: https://mariadb.com/kb/en/is/https://mariadb.com/kb/en/is/ !IS NOTSyntax ------ IS NOT boolean_value Description ----------- Tests a value against a boolean value, where boolean_value can be TRUE, FALSE, or UNKNOWN. Examples -------- SELECT 1 IS NOT UNKNOWN, 0 IS NOT UNKNOWN, NULL IS NOT UNKNOWN; +------------------+------------------+---------------------+ | 1 IS NOT UNKNOWN | 0 IS NOT UNKNOWN | NULL IS NOT UNKNOWN | +------------------+------------------+---------------------+ | 1 | 1 | 0 | +------------------+------------------+---------------------+ SELECT NULL IS NOT TRUE, NULL IS NOT FALSE; +------------------+-------------------+ | NULL IS NOT TRUE | NULL IS NOT FALSE | +------------------+-------------------+ | 1 | 1 | +------------------+-------------------+ URL: https://mariadb.com/kb/en/is-not/https://mariadb.com/kb/en/is-not/"IS NULLSyntax ------ IS NULL Description ----------- Tests whether a value is NULL. See also NULL Values in MariaDB. Examples -------- SELECT 1 IS NULL, 0 IS NULL, NULL IS NULL; +-----------+-----------+--------------+ | 1 IS NULL | 0 IS NULL | NULL IS NULL | +-----------+-----------+--------------+ | 0 | 0 | 1 | +-----------+-----------+--------------+ Compatibility Some ODBC applications use the syntax auto_increment_field IS NOT NULL to find the latest row that was inserted with an autogenerated key value. If your applications need this, you can set the sql_auto_is_null variable to 1. SET @@sql_auto_is_null=1; CREATE TABLE t1 (auto_increment_column INT NOT NULL AUTO_INCREMENT PRIMARY KEY); INSERT INTO t1 VALUES (NULL); SELECT * FROM t1 WHERE auto_increment_column IS NULL; +-----------------------+ | auto_increment_column | +-----------------------+ | 1 | +-----------------------+ URL: https://mariadb.com/kb/en/is-null/https://mariadb.com/kb/en/is-null/I LEASTSyntax ------ LEAST(value1,value2,...) Description ----------- With two or more arguments, returns the smallest (minimum-valued) argument. The arguments are compared using the following rules: If the return value is used in an INTEGER context or all arguments are integer-valued, they are compared as integers. If the return value is used in a REAL context or all arguments are real-valued, they are compared as reals. If any argument is a case-sensitive string, the arguments are compared as case-sensitive strings. In all other cases, the arguments are compared as case-insensitive strings. LEAST() returns NULL if any argument is NULL. Examples -------- SELECT LEAST(2,0); +------------+ | LEAST(2,0) | +------------+ | 0 | +------------+ SELECT LEAST(34.0,3.0,5.0,767.0); +---------------------------+ | LEAST(34.0,3.0,5.0,767.0) | +---------------------------+ | 3.0 | +---------------------------+ SELECT LEAST('B','A','C'); +--------------------+ | LEAST('B','A','C') | +--------------------+ | A | +--------------------+ URL: https://mariadb.com/kb/en/least/https://mariadb.com/kb/en/least/ 0&NOT BETWEENSyntax ------ expr NOT BETWEEN min AND max Description ----------- This is the same as NOT (expr BETWEEN min AND max). Note that the meaning of the alternative form NOT expr BETWEEN min AND max is affected by the HIGH_NOT_PRECEDENCE SQL_MODE flag. Examples -------- SELECT 1 NOT BETWEEN 2 AND 3; +-----------------------+ | 1 NOT BETWEEN 2 AND 3 | +-----------------------+ | 1 | +-----------------------+ SELECT 'b' NOT BETWEEN 'a' AND 'c'; +-----------------------------+ | 'b' NOT BETWEEN 'a' AND 'c' | +-----------------------------+ | 0 | +-----------------------------+ NULL: SELECT 1 NOT BETWEEN 1 AND NULL; +--------------------------+ | 1 NOT BETWEEN 1 AND NULL | +--------------------------+ | NULL | +--------------------------+ URL: https://mariadb.com/kb/en/not-between/https://mariadb.com/kb/en/not-between/i!NOT INSyntax ------ expr NOT IN (value,...) Description ----------- This is the same as NOT (expr IN (value,...)). Examples -------- SELECT 2 NOT IN (0,3,5,7); +--------------------+ | 2 NOT IN (0,3,5,7) | +--------------------+ | 1 | +--------------------+ SELECT 'wefwf' NOT IN ('wee','wefwf','weg'); +--------------------------------------+ | 'wefwf' NOT IN ('wee','wefwf','weg') | +--------------------------------------+ | 0 | +--------------------------------------+ SELECT 1 NOT IN ('1', '2', '3'); +--------------------------+ | 1 NOT IN ('1', '2', '3') | +--------------------------+ | 0 | +--------------------------+ NULL: SELECT NULL NOT IN (1, 2, 3); +-----------------------+ | NULL NOT IN (1, 2, 3) | +-----------------------+ | NULL | +-----------------------+ SELECT 1 NOT IN (1, 2, NULL); +-----------------------+ | 1 NOT IN (1, 2, NULL) | +-----------------------+ | 0 | +-----------------------+ SELECT 5 NOT IN (1, 2, NULL); +-----------------------+ | 5 NOT IN (1, 2, NULL) | +-----------------------+ | NULL | +-----------------------+ URL: https://mariadb.com/kb/en/not-in/https://mariadb.com/kb/en/not-in/ &ST_DISTANCEST_DISTANCE() was introduced in MariaDB 5.3.3. Syntax ------ ST_DISTANCE(g1,g2) Description ----------- Returns the distance between two geometries, or null if not given valid inputs. Example SELECT ST_Distance(POINT(1,2),POINT(2,2)); +------------------------------------+ | ST_Distance(POINT(1,2),POINT(2,2)) | +------------------------------------+ | 1 | +------------------------------------+ URL: https://mariadb.com/kb/en/st_distance/https://mariadb.com/kb/en/st_distance/ $ST_LENGTHSyntax ------ ST_LENGTH(ls) Description ----------- Returns as a double-precision number the length of the LineString value ls in its associated spatial reference. Examples -------- SET @ls = 'LineString(1 1,2 2,3 3)'; SELECT ST_LENGTH(ST_GeomFromText(@ls)); +---------------------------------+ | ST_LENGTH(ST_GeomFromText(@ls)) | +---------------------------------+ | 2.82842712474619 | +---------------------------------+ URL: https://mariadb.com/kb/en/st_length/https://mariadb.com/kb/en/st_length/ &ST_OVERLAPSSyntax ------ ST_OVERLAPS(g1,g2) Description ----------- Returns 1 or 0 to indicate whether geometry g1 spatially overlaps geometry g2. The term spatially overlaps is used if two geometries intersect and their intersection results in a geometry of the same dimension but not equal to either of the given geometries. ST_OVERLAPS() uses object shapes, while OVERLAPS(), based on the original MySQL implementation, uses object bounding rectangles. URL: https://mariadb.com/kb/en/st-overlaps/https://mariadb.com/kb/en/st-overlaps/zAS'@3o |? |? ' &ParenthesesParentheses are sometimes called precedence operators - this means that they can be used to change the other operator's precedence in an expression. The expressions that are written between parentheses are computed before the expressions that are written outside. Parentheses must always contain an expression (that is, they cannot be empty), and can be nested. For example, the following expressions could return different results: NOT a OR b NOT (a OR b) In the first case, NOT applies to a, so if a is FALSE or b is TRUE, the expression returns TRUE. In the second case, NOT applies to the result of a OR b, so if at least one of a or b is TRUE, the expression is TRUE. When the precedence of operators is not intuitive, you can use parentheses to make it immediately clear for whoever reads the statement. The precedence of the NOT operator can also be affected by the HIGH_NOT_PRECEDENCE SQL_MODE flag. Other uses Parentheses must always be used to enclose subqueries. Parentheses can also be used in a JOIN statement between multiple tables to determine which tables must be joined first. Also, parentheses are used to enclose the list of parameters to be passed to built-in functions, user-defined functions and stored routines. However, when no parameter is passed to a stored procedure, parentheses are optional. For builtin functions and user-defined functions, spaces are not allowed between the function name and the open parenthesis, unless the IGNORE_SPACE SQL_MODE is set. For stored routines (and for functions if IGNORE_SPACE is set) spaces are allowed before the open parenthesis, including tab characters and new line characters. Syntax errors If there are more open parentheses than closed parentheses, the error usually looks like this: ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' a t line 1 Note the empty string. If there are more closed parentheses than open parentheses, the error usually looks like this: ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ')' at line 1 Note the quoted closed parenthesis. URL: https://mariadb.com/kb/en/parentheses/https://mariadb.com/kb/en/parentheses/ j(ANALYZE TABLESyntax ------ ANALYZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name [,tbl_name ...] [PERSISTENT FOR [ALL|COLUMNS ([col_name [,col_name ...]])] [INDEXES ([index_name [,index_name ...]])]] Description ----------- ANALYZE TABLE analyzes and stores the key distribution for a table (index statistics). During the analysis, the table is locked with a read lock. This statement works with MyISAM, Aria and InnoDB tables. For MyISAM tables, this statement is equivalent to using myisamchk --analyze. For more information on how the analysis works within InnoDB, see InnoDB Limitations. MariaDB uses the stored key distribution to decide the order in which tables should be joined when you perform a join on something other than a constant. In addition, key distributions can be used when deciding which indexes to use for a specific table within a query. This statement requires SELECT and INSERT privileges for the table. By default, ANALYZE TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log. ANALYZE TABLE is also supported for partitioned tables. You can use ALTER TABLE ... ANALYZE PARTITION to analyze one or more partitions. The Aria storage engine supports progress reporting for the ANALYZE TABLE statement. Engine-Independent Statistics In MariaDB 10.0 and later, ANALYZE TABLE supports engine-independent statistics. See Engine-Independent Table Statistics: Collecting Statistics with the ANALYZE TABLE Statement for more information. URL: https://mariadb.com/kb/en/analyze-table/https://mariadb.com/kb/en/analyze-table/ 3CHECK TABLESyntax ------ CHECK TABLE tbl_name [, tbl_name] ... [option] ... option = {FOR UPGRADE | QUICK | FAST | MEDIUM | EXTENDED | CHANGED} Description ----------- CHECK TABLE checks a table or tables for errors. CHECK TABLE works for Archive, Aria, CSV, InnoDB, and MyISAM tables. For Aria and MyISAM tables, the key statistics are updated as well. For CSV, see also Checking and Repairing CSV Tables. As an alternative, myisamchk is a commandline tool for checking MyISAM tables when the tables are not being accessed. For checking dynamic columns integrity, COLUMN_CHECK() can be used. CHECK TABLE can also check views for problems, such as tables that are referenced in the view definition that no longer exist. CHECK TABLE is also supported for partitioned tables. You can use ALTER TABLE ... CHECK PARTITION to check one or more partitions. The meaning of the different options are as follows - note that this can vary a bit between storage engines: FOR UPGRADE | Do a very quick check if the storage format for the table has changed so that one needs to do a REPAIR. This is only needed when one upgrades between major versions of MariaDB or MySQL. This is usually done by running mysql_upgrade. | FAST | Only check tables that has not been closed properly or are marked as corrupt. Only supported by the MyISAM and Aria engines. For other engines the table is checked normally | CHANGED | Check only tables that has changed since last REPAIR / CHECK. Only supported by the MyISAM and Aria engines. For other engines the table is checked normally. | QUICK | Do a fast check. For MyISAM and Aria engine this means we skip checking the delete link chain which may take some time. | MEDIUM | Scan also the data files. Checks integrity between data and index files with checksums. In most cases this should find all possible errors. | EXTENDED | Does a full check to verify every possible error. For MyISAM and Aria we verify for each row that all it keys exists and points to the row. This may take a long time on big tables! | For most cases running CHECK TABLE without options or MEDIUM should be good enough. Since MariaDB 5.3, the Aria storage engine supports progress reporting for this statement. If you want to know if two tables are identical, take a look at CHECKSUM TABLE. XtraDB/InnoDB If CHECK TABLE finds an error in an InnoDB table, MariaDB might shutdown to prevent the error propagation. In this case, the problem will be reported in the error log. Otherwise, since MariaDB 5.5, the table or an index might be marked as corrupted, to prevent use. This does not happen with some minor problems, like a wrong number of entries in a secondary index. Those problems are reported in the output of CHECK TABLE. Each tablespace contains a header with metadata. This header is not checked by this statement. During the execution of CHECK TABLE, other threads may be blocked. URL: https://mariadb.com/kb/en/sql-commands-check-table/https://mariadb.com/kb/en/sql-commands-check-table/"TOUCHESSyntax ------ Touches(g1,g2) Description ----------- Returns 1 or 0 to indicate whether g1 spatially touches g2. Two geometries spatially touch if the interiors of the geometries do not intersect, but the boundary of one of the geometries intersects either the boundary or the interior of the other. TOUCHES() is based on the original MySQL implementation and uses object bounding rectangles, while ST_TOUCHES() uses object shapes. URL: https://mariadb.com/kb/en/touches/https://mariadb.com/kb/en/touches/&& r  f AR1Q)OPTIMIZE TABLESyntax ------ OPTIMIZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name [, tbl_name] ... [WAIT n | NOWAIT] Description ----------- OPTIMIZE TABLE has two main functions. It can either be used to defragment tables, or to update the InnoDB fulltext index. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. Defragmenting OPTIMIZE TABLE works for InnoDB (before MariaDB 10.1.1, only if the innodb_file_per_table server system variable is set), Aria, MyISAM and ARCHIVE tables, and should be used if you have deleted a large part of a table or if you have made many changes to a table with variable-length rows (tables that have VARCHAR, VARBINARY, BLOB, or TEXT columns). Deleted rows are maintained in a linked list and subsequent INSERT operations reuse old row positions. This statement requires SELECT and INSERT privileges for the table. By default, OPTIMIZE TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log. OPTIMIZE TABLE is also supported for partitioned tables. You can use ALTER TABLE ... OPTIMIZE PARTITION to optimize one or more partitions. You can use OPTIMIZE TABLE to reclaim the unused space and to defragment the data file. With other storage engines, OPTIMIZE TABLE does nothing by default, and returns this message: " The storage engine for the table doesn't support optimize". However, if the server has been started with the --skip-new option, OPTIMIZE TABLE is linked to ALTER TABLE, and recreates the table. This operation frees the unused space and updates index statistics. Since MariaDB 5.3, the Aria storage engine supports progress reporting for this statement. If a MyISAM table is fragmented, concurrent inserts will not be performed until an OPTIMIZE TABLE statement is executed on that table, unless the concurrent_insert server system variable is set to ALWAYS. Updating an InnoDB fulltext index When rows are added or deleted to an InnoDB fulltext index, the index is not immediately re-organized, as this can be an expensive operation. Change statistics are stored in a separate location . The fulltext index is only fully re-organized when an OPTIMIZE TABLE statement is run. By default, an OPTIMIZE TABLE will defragment a table. In order to use it to update fulltext index statistics, the innodb_optimize_fulltext_only system variable must be set to 1. This is intended to be a temporary setting, and should be reset to 0 once the fulltext index has been re-organized. Since fulltext re-organization can take a long time, the innodb_ft_num_word_optimize variable limits the re-organization to a number of words (2000 by default). You can run multiple OPTIMIZE statements to fully re-organize the index. Defragmenting InnoDB tablespaces MariaDB 10.1.1 merged the Facebook/Kakao defragmentation patch MariaDB 10.1.1 merged the Facebook/Kakao defragmentation patch, allowing one to use OPTIMIZE TABLE to defragment InnoDB tablespaces. For this functionality to be enabled, the innodb_defragment system variable must be enabled. No new tables are created and there is no need to copy data from old tables to new tables. Instead, this feature loads n pages (determined by innodb-defragment-n-pages) and tries to move records so that pages would be full of records and then frees pages that are fully empty after the operation. Note that tablespace files (including ibdata1) will not shrink as the result of defragmentation, but one will get better memory utilization in the InnoDB buffer pool as there are fewer data pages in use. See Defragmenting InnoDB Tablespaces for more details. URL: https://mariadb.com/kb/en/optimize-table/https://mariadb.com/kb/en/optimize-table/ 'REPAIR TABLESyntax ------ REPAIR [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name [, tbl_name] ... [QUICK] [EXTENDED] [USE_FRM] Description ----------- REPAIR TABLE repairs a possibly corrupted table. By default, it has the same effect as myisamchk --recover tbl_name or aria_chk --recover tbl_name See aria_chk and myisamchk for more. REPAIR TABLE works for Archive, Aria, CSV and MyISAM tables. For XtraDB/InnoDB, see recovery modes. For CSV, see also Checking and Repairing CSV Tables. For Archive, this statement also improves compression. If the storage engine does not support this statement, a warning is issued. This statement requires SELECT and INSERT privileges for the table. By default, REPAIR TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log. When an index is recreated, the storage engine may use a configurable buffer in the process. Incrementing the buffer speeds up the index creation. Aria and MyISAM allocate a buffer whose size is defined by aria_sort_buffer_size or myisam_sort_buffer_size, also used for ALTER TABLE. REPAIR TABLE is also supported for partitioned tables. However, the USE_FRM option cannot be used with this statement on a partitioned table. ALTER TABLE ... REPAIR PARTITION can be used to repair one or more partitions. The Aria storage engine supports progress reporting for this statement. URL: https://mariadb.com/kb/en/repair-table/https://mariadb.com/kb/en/repair-table/"CURDATESyntax ------ CURDATE() Description ----------- Returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context. Examples -------- SELECT CURDATE(); +------------+ | CURDATE() | +------------+ | 2019-03-05 | +------------+ In a numeric context (note this is not performing date calculations): SELECT CURDATE() +0; +--------------+ | CURDATE() +0 | +--------------+ | 20190305 | +--------------+ Data calculation: SELECT CURDATE() - INTERVAL 5 DAY; +----------------------------+ | CURDATE() - INTERVAL 5 DAY | +----------------------------+ | 2019-02-28 | +----------------------------+ URL: https://mariadb.com/kb/en/curdate/https://mariadb.com/kb/en/curdate/ 'CURRENT_DATESyntax ------ CURRENT_DATE, CURRENT_DATE() Description ----------- CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE(). URL: https://mariadb.com/kb/en/current_date/https://mariadb.com/kb/en/current_date/ 'CURRENT_TIMESyntax ------ CURRENT_TIME CURRENT_TIME([precision]) Description ----------- CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME(). URL: https://mariadb.com/kb/en/current_time/https://mariadb.com/kb/en/current_time/,CURRENT_TIMESTAMPSyntax ------ CURRENT_TIMESTAMP CURRENT_TIMESTAMP([precision]) Description ----------- CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for NOW(). URL: https://mariadb.com/kb/en/current_timestamp/https://mariadb.com/kb/en/current_timestamp/"CURTIMESyntax ------ CURTIME([precision]) Description ----------- Returns the current time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone. The optional precision determines the microsecond precision. See Microseconds in MariaDB. Examples -------- SELECT CURTIME(); +-----------+ | CURTIME() | +-----------+ | 12:45:39 | +-----------+ SELECT CURTIME() + 0; +---------------+ | CURTIME() + 0 | +---------------+ | 124545.000000 | +---------------+ With precision: SELECT CURTIME(2); +-------------+ | CURTIME(2) | +-------------+ | 09:49:08.09 | +-------------+ URL: https://mariadb.com/kb/en/curtime/https://mariadb.com/kb/en/curtime/vY[Y:D  b&REPAIR VIEWREPAIR VIEW was introduced in MariaDB 10.0.18 and MariaDB 5.5.43. Syntax ------ REPAIR [NO_WRITE_TO_BINLOG | LOCAL] VIEW view_name[, view_name] ... [FROM MYSQL] Description ----------- The REPAIR VIEW statement was introduced to assist with fixing MDEV-6916, an issue introduced in MariaDB 5.2 where the view algorithms were swapped compared to their MySQL on disk representation. It checks whether the view algorithm is correct. It is run as part of mysql_upgrade, and should not normally be required in regular use. By default it corrects the checksum and if necessary adds the mariadb-version field. If the optional FROM MYSQL clause is used, and no mariadb-version field is present, the MERGE and TEMPTABLE algorithms are toggled. By default, REPAIR VIEW statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log. Note that REPAIR VIEW in MariaDB 10.0.18 and MariaDB 5.5.43 could crash the server (see MDEV-8115). Upgrade to a later version. URL: https://mariadb.com/kb/en/repair-view/https://mariadb.com/kb/en/repair-view/u.CREATE FUNCTION UDFSyntax ------ CREATE [OR REPLACE] [AGGREGATE] FUNCTION [IF NOT EXISTS] function_name RETURNS {STRING|INTEGER|REAL|DECIMAL} SONAME shared_library_name Description ----------- A user-defined function (UDF) is a way to extend MariaDB with a new function that works like a native (built-in) MariaDB function such as ABS() or CONCAT(). function_name is the name that should be used in SQL statements to invoke the function. To create a function, you must have the INSERT privilege for the mysql database. This is necessary because CREATE FUNCTION adds a row to the mysql.func system table that records the function's name, type, and shared library name. If you do not have this table, you should run the mysql_upgrade command to create it. UDFs need to be written in C, C++ or another language that uses C calling conventions, MariaDB needs to have been dynamically compiled, and your operating system must support dynamic loading. For an example, see sql/udf_example.cc in the source tree. For a collection of existing UDFs see http://www.mysqludf.org/. Statements making use of user-defined functions are not safe for replication. For creating a stored function as opposed to a user-defined function, see CREATE FUNCTION. For valid identifiers to use as function names, see Identifier Names. RETURNS The RETURNS clause indicates the type of the function's return value, and can be one of STRING, INTEGER, REAL or DECIMAL. DECIMAL functions currently return string values and should be written like STRING functions. shared_library_name shared_library_name is the basename of the shared object file that contains the code that implements the function. The file must be located in the plugin directory. This directory is given by the value of the plugin_dir system variable. Note that before MariaDB/MySQL 5.1, the shared object could be located in any directory that was searched by your system's dynamic linker. AGGREGATE Aggregate functions are summary functions such as SUM() and AVG(). Aggregate UDF functions can be used as window functions. OR REPLACE The OR REPLACE clause was added in MariaDB 10.1.3 If the optional OR REPLACE clause is used, it acts as a shortcut for: DROP FUNCTION IF EXISTS function_name; CREATE FUNCTION name ...; IF NOT EXISTS The IF NOT EXISTS clause was added in MariaDB 10.1.3 When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified function already exists. Cannot be used together with OR REPLACE. Upgrading a UDF To upgrade the UDF's shared library, first run a DROP FUNCTION statement, then upgrade the shared library and finally run the CREATE FUNCTION statement. If you upgrade without following this process, you may crash the server. Examples -------- CREATE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so'; Query OK, 0 rows affected (0.00 sec) OR REPLACE and IF NOT EXISTS: CREATE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so'; ERROR 1125 (HY000): Function 'jsoncontains_path' already exists CREATE OR REPLACE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so'; Query OK, 0 rows affected (0.00 sec) CREATE FUNCTION IF NOT EXISTS jsoncontains_path RETURNS integer SONAME 'ha_connect.so'; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+---------------------------------------------+ | Level | Code | Message | +-------+------+---------------------------------------------+ | Note | 1125 | Function 'jsoncontains_path' already exists | +-------+------+---------------------------------------------+ URL: https://mariadb.com/kb/en/create-function-udf/https://mariadb.com/kb/en/create-function-udf/ (DATE FUNCTIONSyntax ------ DATE(expr) Description ----------- Extracts the date part of the date or datetime expression expr. Examples -------- SELECT DATE('2013-07-18 12:21:32'); +-----------------------------+ | DATE('2013-07-18 12:21:32') | +-----------------------------+ | 2013-07-18 | +-----------------------------+ Error Handling Until MariaDB 5.5.32, some versions of MariaDB returned 0000-00-00 when passed an invalid date. From 5.5.32, NULL is returned. URL: https://mariadb.com/kb/en/date-function/https://mariadb.com/kb/en/date-function/DAYSyntax ------ DAY(date) Description ----------- DAY() is a synonym for DAYOFMONTH(). URL: https://mariadb.com/kb/en/day/https://mariadb.com/kb/en/day/ ^$DAYOFYEARSyntax ------ DAYOFYEAR(date) Description ----------- Returns the day of the year for date, in the range 1 to 366. Examples -------- SELECT DAYOFYEAR('2018-02-16'); +-------------------------+ | DAYOFYEAR('2018-02-16') | +-------------------------+ | 47 | +-------------------------+ URL: https://mariadb.com/kb/en/dayofyear/https://mariadb.com/kb/en/dayofyear/ $FROM_DAYSSyntax ------ FROM_DAYS(N) Description ----------- Given a day number N, returns a DATE value. The day count is based on the number of days from the start of the standard calendar (0000-00-00). The function is not designed for use with dates before the advent of the Gregorian calendar in October 1582. Results will not be reliable since it doesn't account for the lost days when the calendar changed from the Julian calendar. This is the converse of the TO_DAYS() function. Examples -------- SELECT FROM_DAYS(730669); +-------------------+ | FROM_DAYS(730669) | +-------------------+ | 2000-07-03 | +-------------------+ URL: https://mariadb.com/kb/en/from_days/https://mariadb.com/kb/en/from_days/ $LOCALTIMESyntax ------ LOCALTIME LOCALTIME([precision]) Description ----------- LOCALTIME and LOCALTIME() are synonyms for NOW(). URL: https://mariadb.com/kb/en/localtime/https://mariadb.com/kb/en/localtime/)LOCALTIMESTAMPSyntax ------ LOCALTIMESTAMP LOCALTIMESTAMP([precision]) Description ----------- LOCALTIMESTAMP and LOCALTIMESTAMP() are synonyms for NOW(). URL: https://mariadb.com/kb/en/localtimestamp/https://mariadb.com/kb/en/localtimestamp/qQ ^+;),DROP FUNCTION UDFSyntax ------ DROP FUNCTION [IF EXISTS] function_name Description ----------- This statement drops the user-defined function (UDF) named function_name. To drop a function, you must have the DELETE privilege for the mysql database. This is because DROP FUNCTION removes the row from the mysql.func system table that records the function's name, type and shared library name. For dropping a stored function, see DROP FUNCTION. Upgrading a UDF To upgrade the UDF's shared library, first run a DROP FUNCTION statement, then upgrade the shared library and finally run the CREATE FUNCTION statement. If you upgrade without following this process, you may crash the server. Examples -------- DROP FUNCTION jsoncontains_path; IF EXISTS: DROP FUNCTION jsoncontains_path; ERROR 1305 (42000): FUNCTION test.jsoncontains_path does not exist DROP FUNCTION IF EXISTS jsoncontains_path; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+------------------------------------------------+ | Level | Code | Message | +-------+------+------------------------------------------------+ | Note | 1305 | FUNCTION test.jsoncontains_path does not exist | +-------+------+------------------------------------------------+ URL: https://mariadb.com/kb/en/drop-function-udf/https://mariadb.com/kb/en/drop-function-udf/:Creating User-Defined FunctionsUser-defined functions allow MariaDB to be extended with a new function that works like a native (built-in) MariaDB function such as ABS() or CONCAT(). There are alternative ways to add a new function: writing a native function (which requires modifying and compiling the server source code), or writing a stored function. Statements making use of user-defined functions are not safe for replication. Functions are written in C or C++, and to make use of them, the operating system must support dynamic loading. Each new SQL function requires corresponding functions written in C/C++. In the list below, at least the main function - x() - and one other, are required. x should be replaced by the name of the function you are creating. All functions need to be thread-safe, so not global or static variables that change can be allocated. Memory is allocated in x_init()/ and freed in x_deinit(). Simple Functions x() Required for all UDF's, this is where the results are calculated. C/C++ type | SQL type | char * | STRING | long long | INTEGER | double | REAL | DECIMAL functions return string values, and so should be written accordingly. It is not possible to create ROW functions. x_init() Initialization function for x(). Can be used for the following: Check the number of arguments to X() (the SQL equivalent). Verify the argument types, or to force arguments to be of a particular type after the function is called. Specify whether the result can be NULL. Specify the maximum result length. For REAL functions, specify the maximum number of decimals for the result. Allocate any required memory. To verify that the arguments are of a required type or, alternatively, to tell MySQL to coerce arguments to the required types when the main function is called. x_deinit() De-initialization function for x(). Used to de-allocate memory that was allocated in x_init(). Description ----------- Each time the SQL function X() is called: MariaDB will first call the C/C++ initialization function, x_init(), assuming it exists. All setup will be performed, and if it returns an error, the SQL statement is aborted and no further functions are called. If there is no x_init() function, or it has been called and did not return an error, x() is then called once per row. After all rows have finished processing, x_deinit() is called, if present, to clean up by de-allocating any memory that was allocated in x_init(). See User-defined Functions Calling Sequences for more details on the functions. Aggregate Functions The following functions are required for aggregate functions, such as AVG() and SUM(). x_clear() Used to reset the current aggregate, but without inserting the argument as the initial aggregate value for the new group. x_add() Used to add the argument to the current aggregate. x_remove() Staring from MariaDB 10.4 it improves the support of window functions (so it is not obligatory to add it) and should remove the argument from the current aggregate. Description ----------- Each time the aggregate SQL function X() is called: MariaDB will first call the C/C++ initialization function, x_init(), assuming it exists. All setup will be performed, and if it returns an error, the SQL statement is aborted and no further functions are called. If there is no x_init() function, or it has been called and did not return an error, x() is then called once per row. After all rows have finished processing, x_deinit() is called, if present, to clean up by de-allocating any memory that was allocated in x_init(). MariaDB will first call the C/C++ initialization function, x_init(), assuming it exists. All setup will be performed, and if it returns an error, the SQL statement is aborted and no further functions are called. The table is sorted according to the GROUP BY expression. x_clear() is called for the first row of each new group. x_add() is called once per row for each row in the same group. x() is called when the group changes, or after the last row, to get the aggregate result. The latter three steps are repeated until all rows have been processed. After all rows have finished processing, x_deinit() is called, if present, to clean up by de-allocating any memory that was allocated in x_init(). Examples -------- For an example, see sql/udf_example.cc in the source tree. For a collection of existing UDFs see https://github.com/mysqludf. URL: https://mariadb.com/kb/en/creating-user-defined-functions/https://mariadb.com/kb/en/creating-user-defined-functions/!MINUTESyntax ------ MINUTE(time) Description ----------- Returns the minute for time, in the range 0 to 59. Examples -------- SELECT MINUTE('2013-08-03 11:04:03'); +-------------------------------+ | MINUTE('2013-08-03 11:04:03') | +-------------------------------+ | 4 | +-------------------------------+ SELECT MINUTE ('23:12:50'); +---------------------+ | MINUTE ('23:12:50') | +---------------------+ | 12 | +---------------------+ URL: https://mariadb.com/kb/en/minute/https://mariadb.com/kb/en/minute/" MONTHSyntax ------ MONTH(date) Description ----------- Returns the month for date in the range 1 to 12 for January to December, or 0 for dates such as '0000-00-00' or '2008-00-00' that have a zero month part. Examples -------- SELECT MONTH('2019-01-03'); +---------------------+ | MONTH('2019-01-03') | +---------------------+ | 1 | +---------------------+ SELECT MONTH('2019-00-03'); +---------------------+ | MONTH('2019-00-03') | +---------------------+ | 0 | +---------------------+ URL: https://mariadb.com/kb/en/month/https://mariadb.com/kb/en/month/ $MONTHNAMESyntax ------ MONTHNAME(date) Description ----------- Returns the full name of the month for date. The language used for the name is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales. Examples -------- SELECT MONTHNAME('2019-02-03'); +-------------------------+ | MONTHNAME('2019-02-03') | +-------------------------+ | February | +-------------------------+ Changing the locale: SET lc_time_names = 'fr_CA'; SELECT MONTHNAME('2019-05-21'); +-------------------------+ | MONTHNAME('2019-05-21') | +-------------------------+ | mai | +-------------------------+ URL: https://mariadb.com/kb/en/monthname/https://mariadb.com/kb/en/monthname/Uy' t(PCUser-Defined Functions Calling SequencesThe functions described in Creating User-defined Functions are expanded on this page. They are declared as follows: Simple Functions x() If x() returns an integer, it is declared as follows: long long x(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error); If x() returns a string (DECIMAL functions also return string values), it is declared as follows: char *x(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long *length, char *is_null, char *error); If x() returns a real, it is declared as follows: double x(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error); x_init() my_bool x_init(UDF_INIT *initid, UDF_ARGS *args, char *message); x_deinit() void x_deinit(UDF_INIT *initid); Description ----------- initid is a parameter passed to all three functions that points to a UDF_INIT structure, used for communicating information between the functions. Its structure members are: my_bool maybe_null maybe_null should be set to 1 if x_init can return a NULL value, Defaults to 1 if any arguments are declared maybe_null. unsigned int decimals Number of decimals after the decimal point. The default, if an explicit number of decimals is passed in the arguments to the main function, is the maximum number of decimals, so if 9.5, 9.55 and 9.555 are passed to the function, the default would be three (based on 9.555, the maximum). If there are no explicit number of decimals, the default is set to 31, or one more than the maximum for the DOUBLE, FLOAT and DECIMAL types. This default can be changed in the function to suit the actual calculation. unsigned int max_length Maximum length of the result. For integers, the default is 21. For strings, the length of the longest argument. For reals, the default is 13 plus the number of decimals indicated by initid->decimals. The length includes any signs or decimal points. Can also be set to 65KB or 16MB in order to return a BLOB. The memory remains unallocated, but this is used to decide on the data type to use if the data needs to be temporarily stored. char *ptr A pointer for use as required by the function. Commonly, initid->ptr is used to communicate allocated memory, with x_init() allocating the memory and assigning it to this pointer, x() using it, and x_deinit() de-allocating it. my_bool const_item Should be set to 1 in x_init() if x() always returns the same value, otherwise 0. Aggregate Functions x_clear() x_clear() is a required function for aggregate functions, and is declared as follows: void x_clear(UDF_INIT *initid, char *is_null, char *error); It is called when the summary results need to be reset, that is at the beginning of each new group. but also to reset the values when there were no matching rows. is_null is set to point to CHAR(0) before calling x_clear(). In the case of an error, you can store the value to which the error argument points (a single-byte variable, not a string string buffer) in the variable. x_reset() x_reset() is declared as follows: void x_reset(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error); It is called on finding the first row in a new group. Should reset the summary variables, and then use UDF_ARGS as the first value in the group's internal summary value. The function is not required if the UDF interface uses x_clear(). x_add() x_add() is declared as follows: void x_add(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error); It is called for all rows belonging to the same group, and should be used to add the value in UDF_ARGS to the internal summary variable. x_remove() x_remove() was added in MariaDB 10.4 and is declared as follows (same as x_add()): void x_remove(UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error ); It adds more efficient support of aggregate UDFs as window functions. x_remove() should "subtract" the row (reverse x_add()). In MariaDB 10.4 aggregate UDFs will work as WINDOW functions without x_remove() but it will not be so efficient. If x_remove() supported (defined) detected automatically. URL: https://mariadb.com/kb/en/user-defined-functions-calling-sequences/https://mariadb.com/kb/en/user-defined-functions-calling-sequences/:User-Defined Functions SecurityThe MariaDB server imposes a number of limitations on user-defined functions for security purposes. The INSERT privilege for the mysql database is required to run CREATE FUNCTION, as a record will be added to the mysql.func-table. The DELETE privilege for the mysql database is required to run DROP FUNCTION as the corresponding record will be removed from the mysql.func-table. UDF object files can only be placed in the plugin directory, as specified by the value of the plugin_dir system variable. At least one symbol, beyond the required x() - corresponding to an SQL function X()) - is required. These can be x_init(), x_deinit(), xxx_reset(), x_clear() and x_add() functions (see Creating User-defined Functions). The allow-suspicious-udfs mysqld option (by default unset) provides a workaround, permitting only one symbol to be used. This is not recommended, as it opens the possibility of loading shared objects that are not legitimate user-defined functions. URL: https://mariadb.com/kb/en/user-defined-functions-security/https://mariadb.com/kb/en/user-defined-functions-security/^"QUARTERSyntax ------ QUARTER(date) Description ----------- Returns the quarter of the year for date, in the range 1 to 4. Returns 0 if month contains a zero value, or NULL if the given value is not otherwise a valid date (zero values are accepted). Examples -------- SELECT QUARTER('2008-04-01'); +-----------------------+ | QUARTER('2008-04-01') | +-----------------------+ | 2 | +-----------------------+ SELECT QUARTER('2019-00-01'); +-----------------------+ | QUARTER('2019-00-01') | +-----------------------+ | 0 | +-----------------------+ URL: https://mariadb.com/kb/en/quarter/https://mariadb.com/kb/en/quarter/(!SECONDSyntax ------ SECOND(time) Description ----------- Returns the second for a given time (which can include microseconds), in the range 0 to 59, or NULL if not given a valid time value. Examples -------- SELECT SECOND('10:05:03'); +--------------------+ | SECOND('10:05:03') | +--------------------+ | 3 | +--------------------+ SELECT SECOND('10:05:01.999999'); +---------------------------+ | SECOND('10:05:01.999999') | +---------------------------+ | 1 | +---------------------------+ URL: https://mariadb.com/kb/en/second/https://mariadb.com/kb/en/second/ r(TIME FunctionSyntax ------ TIME(expr) Description ----------- Extracts the time part of the time or datetime expression expr and returns it as a string. Examples -------- SELECT TIME('2003-12-31 01:02:03'); +-----------------------------+ | TIME('2003-12-31 01:02:03') | +-----------------------------+ | 01:02:03 | +-----------------------------+ SELECT TIME('2003-12-31 01:02:03.000123'); +------------------------------------+ | TIME('2003-12-31 01:02:03.000123') | +------------------------------------+ | 01:02:03.000123 | +------------------------------------+ URL: https://mariadb.com/kb/en/time-function/https://mariadb.com/kb/en/time-function/G]U PDQ*mysql.func TableThe mysql.func table stores information about user-defined functions (UDFs) created with the CREATE FUNCTION UDF statement. In MariaDB 10.4 and later, this table uses the Aria storage engine. MariaDB until 10.3 In MariaDB 10.3 and before, this table uses the MyISAM storage engine. The mysql.func table contains the following fields: Field | Type | Null | Key | Default | Description | name | char(64) | NO | PRI | | UDF name | ret | tinyint(1) | NO | | 0 | | dl | char(128) | NO | | | Shared library name | type | enum('function','aggregate') | NO | | NULL | Type, either function or aggregate. Aggregate functions are summary functions such as SUM() and AVG(). | Example SELECT * FROM mysql.func; +------------------------------+-----+--------------+-----------+ | name | ret | dl | type | +------------------------------+-----+--------------+-----------+ | spider_direct_sql | 2 | ha_spider.so | function | | spider_bg_direct_sql | 2 | ha_spider.so | aggregate | | spider_ping_table | 2 | ha_spider.so | function | | spider_copy_tables | 2 | ha_spider.so | function | | spider_flush_table_mon_cache | 2 | ha_spider.so | function | +------------------------------+-----+--------------+-----------+ URL: https://mariadb.com/kb/en/mysqlfunc-table/https://mariadb.com/kb/en/mysqlfunc-table/)AUTO_INCREMENTDescription ----------- The AUTO_INCREMENT attribute can be used to generate a unique identity for new rows. When you insert a new record to the table, and the auto_increment field is NULL or DEFAULT, the value will automatically be incremented. This also applies to 0, unless the NO_AUTO_VALUE_ON_ZERO SQL_MODE is enabled. AUTO_INCREMENT columns start from 1 by default. The automatically generated value can never be lower than 0. Each table can have only one AUTO_INCREMENT column. It must defined as a key (not necessarily the PRIMARY KEY or UNIQUE key). In some storage engines (including the default InnoDB), if the key consists of multiple columns, the AUTO_INCREMENT column must be the first column. Storage engines that permit the column to be placed elsewhere are Aria, MyISAM, MERGE, Spider, TokuDB, BLACKHOLE, FederatedX and Federated. CREATE TABLE animals ( id MEDIUMINT NOT NULL AUTO_INCREMENT, name CHAR(30) NOT NULL, PRIMARY KEY (id) ); INSERT INTO animals (name) VALUES ('dog'),('cat'),('penguin'), ('fox'),('whale'),('ostrich'); SELECT * FROM animals; +----+---------+ | id | name | +----+---------+ | 1 | dog | | 2 | cat | | 3 | penguin | | 4 | fox | | 5 | whale | | 6 | ostrich | +----+---------+ SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE. CREATE TABLE t (id SERIAL, c CHAR(1)) ENGINE=InnoDB; SHOW CREATE TABLE t \G *************************** 1. row *************************** Table: t Create Table: CREATE TABLE `t` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `c` char(1) DEFAULT NULL, UNIQUE KEY `id` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 Setting or Changing the Auto_Increment Value You can use an ALTER TABLE statement to assign a new value to the auto_increment table option, or set the insert_id server system variable to change the next AUTO_INCREMENT value inserted by the current session. LAST_INSERT_ID() can be used to see the last AUTO_INCREMENT value inserted by the current session. ALTER TABLE animals AUTO_INCREMENT=8; INSERT INTO animals (name) VALUES ('aardvark'); SELECT * FROM animals; +----+-----------+ | id | name | +----+-----------+ | 1 | dog | | 2 | cat | | 3 | penguin | | 4 | fox | | 5 | whale | | 6 | ostrich | | 8 | aardvark | +----+-----------+ SET insert_id=12; INSERT INTO animals (name) VALUES ('gorilla'); SELECT * FROM animals; +----+-----------+ | id | name | +----+-----------+ | 1 | dog | | 2 | cat | | 3 | penguin | | 4 | fox | | 5 | whale | | 6 | ostrich | | 8 | aardvark | | 12 | gorilla | +----+-----------+ InnoDB/XtraDB Until MariaDB 10.2.3, InnoDB and XtraDB used an auto-increment counter that is stored in memory. When the server restarts, the counter is re-initialized to the highest value used in the table, which cancels the effects of any AUTO_INCREMENT = N option in the table statements. From MariaDB 10.2.4, this restriction has been lifted and AUTO_INCREMENT is persistent. See also AUTO_INCREMENT Handling in XtraDB/InnoDB. Setting Explicit Values It is possible to specify a value for an AUTO_INCREMENT column. The value must not exist in the key. If the new value is higher than the current maximum value, the AUTO_INCREMENT value is updated, so the next value will be higher. If the new value is lower than the current maximum value, the AUTO_INCREMENT value remains unchanged. The following example demonstrates these behaviours: CREATE TABLE t (id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY) ENGINE = InnoDB; INSERT INTO t VALUES (NULL); SELECT id FROM t; +----+ | id | +----+ | 1 | +----+ INSERT INTO t VALUES (10); -- higher value SELECT id FROM t; +----+ | id | +----+ | 1 | | 10 | +----+ INSERT INTO t VALUES (2); -- lower value INSERT INTO t VALUES (NULL); -- auto value SELECT id FROM t; +----+ | id | +----+ | 1 | | 2 | | 10 | | 11 | +----+ The ARCHIVE storage engine does not allow to insert a value that is lower than the current maximum. Missing Values An AUTO_INCREMENT column normally has missing values. This happens because if a row is deleted, or an AUTO_INCREMENT value is explicitly updated, old values are never re-used. The REPLACE statement also deletes a row, and its value is wasted. With InnoDB, values can be reserved by a transaction; but if the transaction fails (for example, because of a ROLLBACK) the reserved value will be lost. Thus AUTO_INCREMENT values can be used to sort results in a chronological order, but not to create a numeric sequence. Replication To make master-master or Galera safe to use AUTO_INCREMENT one should use the system variables auto_increment_increment and auto_increment_offset to generate unique values for each server. CHECK Constraints, DEFAULT Values and Virtual Columns From MariaDB 10.2.6 auto_increment columns are no longer permitted in CHECK constraints, DEFAULT value expressions and virtual columns. They were permitted in earlier versions, but did not work correctly. See MDEV-11117. URL: https://mariadb.com/kb/en/auto_increment/https://mariadb.com/kb/en/auto_increment/ L&TIME_FORMATSyntax ------ TIME_FORMAT(time,format) Description ----------- This is used like the DATE_FORMAT() function, but the format string may contain format specifiers only for hours, minutes, and seconds. Other specifiers produce a NULL value or 0. Examples -------- SELECT TIME_FORMAT('100:00:00', '%H %k %h %I %l'); +--------------------------------------------+ | TIME_FORMAT('100:00:00', '%H %k %h %I %l') | +--------------------------------------------+ | 100 100 04 04 4 | +--------------------------------------------+ URL: https://mariadb.com/kb/en/time_format/https://mariadb.com/kb/en/time_format/ ~&TIME_TO_SECSyntax ------ TIME_TO_SEC(time) Description ----------- Returns the time argument, converted to seconds. The value returned by TIME_TO_SEC is of type DOUBLE. Before MariaDB 5.3 (and MySQL 5.6), the type was INT. See Microseconds in MariaDB. Examples -------- SELECT TIME_TO_SEC('22:23:00'); +-------------------------+ | TIME_TO_SEC('22:23:00') | +-------------------------+ | 80580 | +-------------------------+ SELECT TIME_TO_SEC('00:39:38'); +-------------------------+ | TIME_TO_SEC('00:39:38') | +-------------------------+ | 2378 | +-------------------------+ URL: https://mariadb.com/kb/en/time_to_sec/https://mariadb.com/kb/en/time_to_sec/Sf ZG !BIGINTSyntax ------ BIGINT[(M)] [SIGNED | UNSIGNED | ZEROFILL] Description ----------- A large integer. The signed range is -9223372036854775808 to 9223372036854775807. The unsigned range is 0 to 18446744073709551615. If a column has been set to ZEROFILL, all values will be prepended by zeros so that the BIGINT value contains a number of M digits. Note: If the ZEROFILL attribute has been specified, the column will automatically become UNSIGNED. For more details on the attributes, see Numeric Data Type Overview. SERIAL is an alias for: BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE Examples -------- CREATE TABLE bigints (a BIGINT,b BIGINT UNSIGNED,c BIGINT ZEROFILL); INSERT INTO bigints VALUES (-10,-10,-10); Query OK, 1 row affected, 2 warnings (0.08 sec) Warning (Code 1264): Out of range value for column 'b' at row 1 Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO bigints VALUES (-10,10,-10);Query OK, 1 row affected, 1 warning (0.08 sec) Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO bigints VALUES (-10,10,10); INSERT INTO bigints VALUES (9223372036854775808,9223372036854775808,9223372036854775808); Query OK, 1 row affected, 1 warning (0.07 sec) Warning (Code 1264): Out of range value for column 'a' at row 1 INSERT INTO bigints VALUES (9223372036854775807,9223372036854775808,9223372036854775808); SELECT * FROM bigints; +---------------------+---------------------+----------------------+ | a | b | c | +---------------------+---------------------+----------------------+ | -10 | 0 | 00000000000000000000 | | -10 | 10 | 00000000000000000000 | | -10 | 10 | 00000000000000000010 | | 9223372036854775807 | 9223372036854775808 | 09223372036854775808 | | 9223372036854775807 | 9223372036854775808 | 09223372036854775808 | +---------------------+---------------------+----------------------+ URL: https://mariadb.com/kb/en/bigint/https://mariadb.com/kb/en/bigint/ !BINARYSyntax ------ BINARY(M) Description ----------- The BINARY type is similar to the CHAR type, but stores binary byte strings rather than non-binary character strings. M represents the column length in bytes. It contains no character set, and comparison and sorting are based on the numeric value of the bytes. If the maximum length is exceeded, and SQL strict mode is not enabled , the extra characters will be dropped with a warning. If strict mode is enabled, an error will occur. BINARY values are right-padded with 0x00 (the zero byte) to the specified length when inserted. The padding is not removed on select, so this needs to be taken into account when sorting and comparing, where all bytes are significant. The zero byte, 0x00 is less than a space for comparison purposes. Examples -------- Inserting too many characters, first with strict mode off, then with it on: CREATE TABLE bins (a BINARY(10)); INSERT INTO bins VALUES('12345678901'); Query OK, 1 row affected, 1 warning (0.04 sec) SELECT * FROM bins; +------------+ | a | +------------+ | 1234567890 | +------------+ SET sql_mode='STRICT_ALL_TABLES'; INSERT INTO bins VALUES('12345678901'); ERROR 1406 (22001): Data too long for column 'a' at row 1 Sorting is performed with the byte value: TRUNCATE bins; INSERT INTO bins VALUES('A'),('B'),('a'),('b'); SELECT * FROM bins ORDER BY a; +------+ | a | +------+ | A | | B | | a | | b | +------+ Using CAST to sort as a CHAR instead: SELECT * FROM bins ORDER BY CAST(a AS CHAR); +------+ | a | +------+ | a | | A | | b | | B | +------+ The field is a BINARY(10), so padding of two '\0's are inserted, causing comparisons that don't take this into account to fail: TRUNCATE bins; INSERT INTO bins VALUES('12345678'); SELECT a = '12345678', a = '12345678\0\0' from bins; +----------------+--------------------+ | a = '12345678' | a = '12345678\0\0' | +----------------+--------------------+ | 0 | 1 | +----------------+--------------------+ URL: https://mariadb.com/kb/en/binary/https://mariadb.com/kb/en/binary/ yBITSyntax ------ BIT[(M)] Description ----------- A bit-field type. M indicates the number of bits per value, from 1 to 64. The default is 1 if M is omitted. Bit values can be inserted with b'value' notation, where value is the bit value in 0's and 1's. Bit fields are automatically zero-padded from the left to the full length of the bit, so for example in a BIT(4) field, '10' is equivalent to '0010'. Bits are returned as binary, so to display them, either add 0, or use a function such as HEX, OCT or BIN to convert them. Examples -------- CREATE TEMPORARY TABLE b ( b1 BIT(8) ); INSERT INTO b VALUES (b'11111111'),(b'01010101'),(b'1111111111111'); Query OK, 3 rows affected, 1 warning (0.10 sec) Records: 3 Duplicates: 0 Warnings: 1 SHOW WARNINGS; +---------+------+---------------------------------------------+ | Level | Code | Message | +---------+------+---------------------------------------------+ | Warning | 1264 | Out of range value for column 'b1' at row 3 | +---------+------+---------------------------------------------+ SELECT b1+0, HEX(b1), OCT(b1), BIN(b1) FROM b; +------+---------+---------+----------+ | b1+0 | HEX(b1) | OCT(b1) | BIN(b1) | +------+---------+---------+----------+ | 255 | FF | 377 | 11111111 | | 85 | 55 | 125 | 1010101 | | 255 | FF | 377 | 11111111 | +------+---------+---------+----------+ URL: https://mariadb.com/kb/en/bit/https://mariadb.com/kb/en/bit/ #UTC_DATESyntax ------ UTC_DATE, UTC_DATE() Description ----------- Returns the current UTC date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context. Examples -------- SELECT UTC_DATE(), UTC_DATE() + 0; +------------+----------------+ | UTC_DATE() | UTC_DATE() + 0 | +------------+----------------+ | 2010-03-27 | 20100327 | +------------+----------------+ URL: https://mariadb.com/kb/en/utc_date/https://mariadb.com/kb/en/utc_date/ #UTC_TIMESyntax ------ UTC_TIME UTC_TIME([precision]) Description ----------- Returns the current UTC time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The optional precision determines the microsecond precision. See Microseconds in MariaDB. Examples -------- SELECT UTC_TIME(), UTC_TIME() + 0; +------------+----------------+ | UTC_TIME() | UTC_TIME() + 0 | +------------+----------------+ | 17:32:34 | 173234.000000 | +------------+----------------+ With precision: SELECT UTC_TIME(5); +----------------+ | UTC_TIME(5) | +----------------+ | 07:52:50.78369 | +----------------+ URL: https://mariadb.com/kb/en/utc_time/https://mariadb.com/kb/en/utc_time/[' AsBinaryA synonym for ST_AsBinary(). URL: https://mariadb.com/kb/en/wkb-asbinary/https://mariadb.com/kb/en/wkb-asbinary/T AsWKBA synonym for ST_AsBinary(). URL: https://mariadb.com/kb/en/aswkb/https://mariadb.com/kb/en/aswkb/ ' MLineFromWKBSyntax ------ MLineFromWKB(wkb[,srid]) MultiLineStringFromWKB(wkb[,srid]) Description ----------- Constructs a MULTILINESTRING value using its WKB representation and SRID. MLineFromWKB() and MultiLineStringFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(MLineFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')); SELECT ST_AsText(MLineFromWKB(@g)); +--------------------------------------------------------+ | ST_AsText(MLineFromWKB(@g)) | +--------------------------------------------------------+ | MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48)) | +--------------------------------------------------------+ URL: https://mariadb.com/kb/en/mlinefromwkb/https://mariadb.com/kb/en/mlinefromwkb/U/   BLOBSyntax ------ BLOB[(M)] Description ----------- A BLOB column with a maximum length of 65,535 (216 - 1) bytes. Each BLOB value is stored using a two-byte length prefix that indicates the number of bytes in the value. An optional length M can be given for this type. If this is done, MariaDB creates the column as the smallest BLOB type large enough to hold values M bytes long. BLOBS can also be used to store dynamic columns. Before MariaDB 10.2.1, BLOB and TEXT columns could not be assigned a DEFAULT value. This restriction was lifted in MariaDB 10.2.1. Indexing In MariaDB 10.4, it is possible to set a Unique index on a column that uses the BLOB data type. In previous releases this was not possible, as the index would only guarantee the uniqueness of a fixed number of characters. Oracle Mode In Oracle mode from MariaDB 10.3, BLOB is a synonym for LONGBLOB. URL: https://mariadb.com/kb/en/blob/https://mariadb.com/kb/en/blob/"BOOLEANSyntax ------ BOOL, BOOLEAN Description ----------- These types are synonyms for TINYINT(1). A value of zero is considered false. Non-zero values are considered true: mysql> SELECT IF(0, 'true', 'false'); +------------------------+ | IF(0, 'true', 'false') | +------------------------+ | false | +------------------------+ mysql> SELECT IF(1, 'true', 'false'); +------------------------+ | IF(1, 'true', 'false') | +------------------------+ | true | +------------------------+ mysql> SELECT IF(2, 'true', 'false'); +------------------------+ | IF(2, 'true', 'false') | +------------------------+ | true | +------------------------+ However, the values TRUE and FALSE are merely aliases for 1 and 0, respectively, as shown here: mysql> SELECT IF(0 = FALSE, 'true', 'false'); +--------------------------------+ | IF(0 = FALSE, 'true', 'false') | +--------------------------------+ | true | +--------------------------------+ mysql> SELECT IF(1 = TRUE, 'true', 'false'); +-------------------------------+ | IF(1 = TRUE, 'true', 'false') | +-------------------------------+ | true | +-------------------------------+ mysql> SELECT IF(2 = TRUE, 'true', 'false'); +-------------------------------+ | IF(2 = TRUE, 'true', 'false') | +-------------------------------+ | false | +-------------------------------+ mysql> SELECT IF(2 = FALSE, 'true', 'false'); +--------------------------------+ | IF(2 = FALSE, 'true', 'false') | +--------------------------------+ | false | +--------------------------------+ UNKNOWN is an alias for NULL. The last two statements display the results shown because 2 is equal to neither 1 nor 0. URL: https://mariadb.com/kb/en/boolean/https://mariadb.com/kb/en/boolean/cCHARThis article covers the CHAR data type. See CHAR Function for the function. Syntax ------ [NATIONAL] CHAR[(M)] [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- A fixed-length string that is always right-padded with spaces to the specified length when stored. M represents the column length in characters. The range of M is 0 to 255. If M is omitted, the length is 1. CHAR(0) columns can contain 2 values: an empty string or NULL. Such columns cannot be part of an index. The CONNECT storage engine does not support CHAR(0). Note: Trailing spaces are removed when CHAR values are retrieved unless the PAD_CHAR_TO_FULL_LENGTH SQL mode is enabled. Before MariaDB 10.2, all collations were of type PADSPACE, meaning that CHAR (as well as VARCHAR and TEXT) values are compared without regard for trailing spaces. This does not apply to the LIKE pattern-matching operator, which takes into account trailing spaces. If a unique index consists of a column where trailing pad characters are stripped or ignored, inserts into that column where values differ only by the number of trailing pad characters will result in a duplicate-key error. Examples -------- Trailing spaces: CREATE TABLE strtest (c CHAR(10)); INSERT INTO strtest VALUES('Maria '); SELECT c='Maria',c='Maria ' FROM strtest; +-----------+--------------+ | c='Maria' | c='Maria ' | +-----------+--------------+ | 1 | 1 | +-----------+--------------+ SELECT c LIKE 'Maria',c LIKE 'Maria ' FROM strtest; +----------------+-------------------+ | c LIKE 'Maria' | c LIKE 'Maria ' | +----------------+-------------------+ | 1 | 0 | +----------------+-------------------+ NO PAD Collations NO PAD collations regard trailing spaces as normal characters. You can get a list of all NO PAD collations by querying the Information Schema Collations table, for example: SELECT collation_name FROM information_schema.collations WHERE collation_name LIKE "%nopad%"; +------------------------------+ | collation_name | +------------------------------+ | big5_chinese_nopad_ci | | big5_nopad_bin | ... URL: https://mariadb.com/kb/en/char/https://mariadb.com/kb/en/char/ ( MPointFromWKBSyntax ------ MPointFromWKB(wkb[,srid]) MultiPointFromWKB(wkb[,srid]) Description ----------- Constructs a MULTIPOINT value using its WKB representation and SRID. MPointFromWKB() and MultiPointFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(MPointFromText('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9 3, 8 4, 6 6, 6 9, 4 9, 1 5 )')); SELECT ST_AsText(MPointFromWKB(@g)); +-----------------------------------------------------+ | ST_AsText(MPointFromWKB(@g)) | +-----------------------------------------------------+ | MULTIPOINT(1 1,2 2,5 3,7 2,9 3,8 4,6 6,6 9,4 9,1 5) | +-----------------------------------------------------+ URL: https://mariadb.com/kb/en/mpointfromwkb/https://mariadb.com/kb/en/mpointfromwkb/g. GeomCollFromWKBA synonym for ST_GeomCollFromWKB. URL: https://mariadb.com/kb/en/wkb-geomcollfromwkb/https://mariadb.com/kb/en/wkb-geomcollfromwkb/m4 GeometryCollectionFromWKBA synonym for ST_GeomCollFromWKB. URL: https://mariadb.com/kb/en/geometrycollectionfromwkb/https://mariadb.com/kb/en/geometrycollectionfromwkb/_* GeometryFromWKBA synonym for ST_GeomFromWKB. URL: https://mariadb.com/kb/en/geometryfromwkb/https://mariadb.com/kb/en/geometryfromwkb/ _* GeomFromWKBA synonym for ST_GeomFromWKB. URL: https://mariadb.com/kb/en/wkb-geomfromwkb/https://mariadb.com/kb/en/wkb-geomfromwkb/ _* LineFromWKBA synonym for ST_LineFromWKB. URL: https://mariadb.com/kb/en/wkb-linefromwkb/https://mariadb.com/kb/en/wkb-linefromwkb/a, LineStringFromWKBA synonym for ST_LineFromWKB. URL: https://mariadb.com/kb/en/linestringfromwkb/https://mariadb.com/kb/en/linestringfromwkb/f1 MultiLineStringFromWKBA synonym for MLineFromWKB(). URL: https://mariadb.com/kb/en/multilinestringfromwkb/https://mariadb.com/kb/en/multilinestringfromwkb/`, MultiPointFromWKBA synonym for MPointFromWKB. URL: https://mariadb.com/kb/en/multipointfromwkb/https://mariadb.com/kb/en/multipointfromwkb/_. MultiPolygonFromWKBSynonym for MPolyFromWKB. URL: https://mariadb.com/kb/en/multipolygonfromwkb/https://mariadb.com/kb/en/multipolygonfromwkb/  a+ PointFromWKBA synonym for ST_PointFromWKB. URL: https://mariadb.com/kb/en/wkb-pointfromwkb/https://mariadb.com/kb/en/wkb-pointfromwkb/iUeE?  (NDATESyntax ------ DATE Description ----------- A date. The supported range is '1000-01-01' to '9999-12-31'. MariaDB displays DATE values in 'YYYY-MM-DD' format, but can be assigned dates in looser formats, including strings or numbers, as long as they make sense. These include a short year, YY-MM-DD, no delimiters, YYMMDD, or any other acceptable delimiter, for example YYYY/MM/DD. For details, see date and time literals. '0000-00-00' is a permitted special value (zero-date), unless the NO_ZERO_DATE SQL_MODE is used. Also, individual components of a date can be set to 0 (for example: '2015-00-12'), unless the NO_ZERO_IN_DATE SQL_MODE is used. In many cases, the result of en expression involving a zero-date, or a date with zero-parts, is NULL. If the ALLOW_INVALID_DATES SQL_MODE is enabled, if the day part is in the range between 1 and 31, the date does not produce any error, even for months that have less than 31 days. Examples -------- CREATE TABLE t1 (d DATE); INSERT INTO t1 VALUES ("2010-01-12"), ("2011-2-28"), ('120314'),('13*04*21'); SELECT * FROM t1; +------------+ | d | +------------+ | 2010-01-12 | | 2011-02-28 | | 2012-03-14 | | 2013-04-21 | +------------+ URL: https://mariadb.com/kb/en/date/https://mariadb.com/kb/en/date/#DATETIMESyntax ------ DATETIME [(microsecond precision)] Description ----------- A date and time combination. The supported range is '1000-01-01 00:00:00.000000' to '9999-12-31 23:59:59.999999'. MariaDB displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format, but allows assignment of values to DATETIME columns using either strings or numbers. For details, see date and time literals. The microsecond precision can be from 0-6. If not specified 0 is used. '0000-00-00' is a permitted special value (zero-date), unless the NO_ZERO_DATE SQL_MODE is used. Also, individual components of a date can be set to 0 (for example: '2015-00-12'), unless the NO_ZERO_IN_DATE SQL_MODE is used. In many cases, the result of en expression involving a zero-date, or a date with zero-parts, is NULL. If the ALLOW_INVALID_DATES SQL_MODE is enabled, if the day part is in the range between 1 and 31, the date does not produce any error, even for months that have less than 31 days. Since MariaDB 10.0.1, DATETIME columns also accept CURRENT_TIMESTAMP as the default value. MariaDB 10.1.2 introduced the --mysql56-temporal-format option, on by default, which allows MariaDB to store DATETMEs using the same low-level format MySQL 5.6 uses. For more information, see Internal Format, below. For storage requirements, see Data Type Storage Requirements. Oracle Mode In Oracle mode from MariaDB 10.3, DATE with a time portion is a synonym for DATETIME. Internal Format In MariaDB 10.1.2 a new temporal format was introduced from MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP columns operate at lower levels. These changes allow these temporal data types to have fractional parts and negative values. You can disable this feature using the mysql56_temporal_format system variable. Tables that include TIMESTAMP values that were created on an older version of MariaDB or that were created while the mysql56_temporal_format system variable was disabled continue to store data using the older data type format. In order to update table columns from the older format to the newer format, execute an ALTER TABLE... MODIFY COLUMN statement that changes the column to the *same* data type. This change may be needed if you want to export the table's tablespace and import it onto a server that has mysql56_temporal_format=ON set (see MDEV-15225). For instance, if you have a DATETIME column in your table: SHOW VARIABLES LIKE 'mysql56_temporal_format'; +-------------------------+-------+ | Variable_name | Value | +-------------------------+-------+ | mysql56_temporal_format | ON | +-------------------------+-------+ ALTER TABLE example_table MODIFY ts_col DATETIME; When MariaDB executes the ALTER TABLE statement, it converts the data from the older temporal format to the newer one. In the event that you have several tables and columns using temporal data types that you want to switch over to the new format, make sure the system variable is enabled, then perform a dump and restore using mysqldump. The columns using relevant temporal data types are restored using the new temporal format. Examples -------- CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2011-03-11"), ("2012-04-19 13:08:22"), ("2013-07-18 13:44:22.123456"); SELECT * FROM t1; +---------------------+ | d | +---------------------+ | 2011-03-11 00:00:00 | | 2012-04-19 13:08:22 | | 2013-07-18 13:44:22 | +---------------------+ CREATE TABLE t2 (d DATETIME(6)); INSERT INTO t2 VALUES ("2011-03-11"), ("2012-04-19 13:08:22"), ("2013-07-18 13:44:22.123456"); SELECT * FROM t2; +----------------------------+ | d | +----------------------------+ | 2011-03-11 00:00:00.000000 | | 2012-04-19 13:08:22.000000 | | 2013-07-18 13:44:22.123456 | +----------------------------++ Strings used in datetime context are automatically converted to datetime(6). If you want to have a datetime without seconds, you should use CONVERT(..,datetime). SELECT CONVERT('2007-11-30 10:30:19',datetime); +-----------------------------------------+ | CONVERT('2007-11-30 10:30:19',datetime) | +-----------------------------------------+ | 2007-11-30 10:30:19 | +-----------------------------------------+ SELECT CONVERT('2007-11-30 10:30:19',datetime(6)); +--------------------------------------------+ | CONVERT('2007-11-30 10:30:19',datetime(6)) | +--------------------------------------------+ | 2007-11-30 10:30:19.000000 | +--------------------------------------------+ URL: https://mariadb.com/kb/en/datetime/https://mariadb.com/kb/en/datetime/! _* PolyFromWKBA synonym for ST_PolyFromWKB. URL: https://mariadb.com/kb/en/wkb-polyfromwkb/https://mariadb.com/kb/en/wkb-polyfromwkb/"^) PolygonFromWKBA synonym for ST_PolyFromWKB. URL: https://mariadb.com/kb/en/polygonfromwkb/https://mariadb.com/kb/en/polygonfromwkb/# & ST_AsBinarySyntax ------ ST_AsBinary(g) AsBinary(g) ST_AsWKB(g) AsWKB(g) Description ----------- Converts a value in internal geometry format to its WKB representation and returns the binary result. ST_AsBinary(), AsBinary(), ST_AsWKB() and AsWKB() are synonyms, Examples -------- SET @poly = ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))'); SELECT ST_AsBinary(@poly); SELECT ST_AsText(ST_GeomFromWKB(ST_AsWKB(@poly))); +--------------------------------------------+ | ST_AsText(ST_GeomFromWKB(ST_AsWKB(@poly))) | +--------------------------------------------+ | POLYGON((0 0,0 1,1 1,1 0,0 0)) | +--------------------------------------------+ URL: https://mariadb.com/kb/en/st_asbinary/https://mariadb.com/kb/en/st_asbinary/$W# ST_AsWKBA synonym for ST_AsBinary(). URL: https://mariadb.com/kb/en/st_aswkb/https://mariadb.com/kb/en/st_aswkb/&p7 ST_GeometryCollectionFromWKBA synonym for ST_GeomCollFromWKB. URL: https://mariadb.com/kb/en/st_geometrycollectionfromwkb/https://mariadb.com/kb/en/st_geometrycollectionfromwkb/'b- ST_GeometryFromWKBA synonym for ST_GeomFromWKB. URL: https://mariadb.com/kb/en/st_geometryfromwkb/https://mariadb.com/kb/en/st_geometryfromwkb/>= \%B"DECIMALSyntax ------ DECIMAL[(M[,D])] [SIGNED | UNSIGNED | ZEROFILL] Description ----------- A packed "exact" fixed-point number. M is the total number of digits (the precision) and D is the number of digits after the decimal point (the scale). The decimal point and (for negative numbers) the "-" sign are not counted in M. If D is 0, values have no decimal point or fractional part and on INSERT the value will be rounded to the nearest DECIMAL. The maximum number of digits (M) for DECIMAL is 65. The maximum number of supported decimals (D) is 30 before MariadB 10.2.1 and 38 afterwards. If D is omitted, the default is 0. If M is omitted, the default is 10. UNSIGNED, if specified, disallows negative values. ZEROFILL, if specified, pads the number with zeros, up to the total number of digits specified by M. All basic calculations (+, -, *, /) with DECIMAL columns are done with a precision of 65 digits. For more details on the attributes, see Numeric Data Type Overview. Oracle Mode In Oracle mode from MariaDB 10.3, NUMBER is a synonym. Examples -------- CREATE TABLE t1 (d DECIMAL UNSIGNED ZEROFILL); INSERT INTO t1 VALUES (1),(2),(3),(4.0),(5.2),(5.7); Query OK, 6 rows affected, 2 warnings (0.16 sec) Records: 6 Duplicates: 0 Warnings: 2 Note (Code 1265): Data truncated for column 'd' at row 5 Note (Code 1265): Data truncated for column 'd' at row 6 SELECT * FROM t1; +------------+ | d | +------------+ | 0000000001 | | 0000000002 | | 0000000003 | | 0000000004 | | 0000000005 | | 0000000006 | +------------+ INSERT INTO t1 VALUES (-7); ERROR 1264 (22003): Out of range value for column 'd' at row 1 URL: https://mariadb.com/kb/en/decimal/https://mariadb.com/kb/en/decimal/ENUMSyntax ------ ENUM('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- An enumeration. A string object that can have only one value, chosen from the list of values 'value1', 'value2', ..., NULL or the special '' error value. In theory, an ENUM column can have a maximum of 65,535 distinct values; in practice, the real maximum depends on many factors. ENUM values are represented internally as integers. Trailing spaces are automatically stripped from ENUM values on table creation. ENUMs require relatively little storage space compared to strings, either one or two bytes depending on the number of enumeration values. NULL and empty values An ENUM can also contain NULL and empty values. If the ENUM column is declared to permit NULL values, NULL becomes a valid value, as well as the default value (see below). If strict SQL Mode is not enabled, and an invalid value is inserted into an ENUM, a special empty string, with an index value of zero (see Numeric index, below), is inserted, with a warning. This may be confusing, because the empty string is also a possible value, and the only difference if that in this case its index is not 0. Inserting will fail with an error if strict mode is active. If a DEFAULT clause is missing, the default value will be: NULL is the column is nullable; otherwise, the first value in the enumaration. Numeric index ENUM values are indexed numerically in the order they are defined, and sorting will be performed in this numeric order. We suggest not using ENUM to store numerals, as there is little to no storage space benefit, and it is easy to confuse the enum integer with the enum numeral value by leaving out the quotes. An ENUM defined as ENUM('apple','orange','pear') would have the following index values: Index | Value | NULL | NULL | 0 | '' | 1 | 'apple' | 2 | 'orange' | 3 | 'pear' | Examples -------- CREATE TABLE fruits ( id INT NOT NULL auto_increment PRIMARY KEY, fruit ENUM('apple','orange','pear'), bushels INT); DESCRIBE fruits; +---------+-------------------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------+-------------------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | fruit | enum('apple','orange','pear') | YES | | NULL | | | bushels | int(11) | YES | | NULL | | +---------+-------------------------------+------+-----+---------+----------------+ INSERT INTO fruits (fruit,bushels) VALUES ('pear',20), ('apple',100), ('orange',25); INSERT INTO fruits (fruit,bushels) VALUES ('avocado',10); ERROR 1265 (01000): Data truncated for column 'fruit' at row 1 SELECT * FROM fruits; +----+--------+---------+ | id | fruit | bushels | +----+--------+---------+ | 1 | pear | 20 | | 2 | apple | 100 | | 3 | orange | 25 | +----+--------+---------+ Selecting by numeric index: SELECT * FROM fruits WHERE fruit=2; +----+--------+---------+ | id | fruit | bushels | +----+--------+---------+ | 3 | orange | 25 | +----+--------+---------+ Sorting is according to the index value: CREATE TABLE enums (a ENUM('2','1')); INSERT INTO enums VALUES ('1'),('2'); SELECT * FROM enums ORDER BY a ASC; +------+ | a | +------+ | 2 | | 1 | +------+ It's easy to get confused between returning the enum integer with the stored value, so we don't suggest using ENUM to store numerals. The first example returns the 1st indexed field ('2' has an index value of 1, as it's defined first), while the second example returns the string value '1'. SELECT * FROM enums WHERE a=1; +------+ | a | +------+ | 2 | +------+ SELECT * FROM enums WHERE a='1'; +------+ | a | +------+ | 1 | +------+ URL: https://mariadb.com/kb/en/enum/https://mariadb.com/kb/en/enum/() ST_GeomFromWKBSyntax ------ ST_GeomFromWKB(wkb[,srid]) ST_GeometryFromWKB(wkb[,srid]) GeomFromWKB(wkb[,srid]) GeometryFromWKB(wkb[,srid]) Description ----------- Constructs a geometry value of any type using its WKB representation and SRID. ST_GeomFromWKB(), ST_GeometryFromWKB(), GeomFromWKB() and GeometryFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(ST_LineFromText('LINESTRING(0 4, 4 6)')); SELECT ST_AsText(ST_GeomFromWKB(@g)); +-------------------------------+ | ST_AsText(ST_GeomFromWKB(@g)) | +-------------------------------+ | LINESTRING(0 4,4 6) | +-------------------------------+ URL: https://mariadb.com/kb/en/st_geomfromwkb/https://mariadb.com/kb/en/st_geomfromwkb/)j) ST_LineFromWKBSyntax ------ ST_LineFromWKB(wkb[,srid]) LineFromWKB(wkb[,srid]) ST_LineStringFromWKB(wkb[,srid]) LineStringFromWKB(wkb[,srid]) Description ----------- Constructs a LINESTRING value using its WKB representation and SRID. ST_LineFromWKB(), LineFromWKB(), ST_LineStringFromWKB(), and LineStringFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(ST_LineFromText('LineString(0 4,4 6)')); SELECT ST_AsText(ST_LineFromWKB(@g)) AS l; +---------------------+ | l | +---------------------+ | LINESTRING(0 4,4 6) | +---------------------+ URL: https://mariadb.com/kb/en/st_linefromwkb/https://mariadb.com/kb/en/st_linefromwkb/*d/ ST_LineStringFromWKBA synonym for ST_LineFromWKB. URL: https://mariadb.com/kb/en/st_linestringfromwkb/https://mariadb.com/kb/en/st_linestringfromwkb/+* ST_PointFromWKBSyntax ------ ST_PointFromWKB(wkb[,srid]) PointFromWKB(wkb[,srid]) Description ----------- Constructs a POINT value using its WKB representation and SRID. ST_PointFromWKB() and PointFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(ST_PointFromText('POINT(0 4)')); SELECT ST_AsText(ST_PointFromWKB(@g)) AS p; +------------+ | p | +------------+ | POINT(0 4) | +------------+ URL: https://mariadb.com/kb/en/st_pointfromwkb/https://mariadb.com/kb/en/st_pointfromwkb/<! 87& !DOUBLESyntax ------ DOUBLE[(M,D)] [SIGNED | UNSIGNED | ZEROFILL] DOUBLE PRECISION[(M,D)] [SIGNED | UNSIGNED | ZEROFILL] REAL[(M,D)] [SIGNED | UNSIGNED | ZEROFILL] Description ----------- A normal-size (double-precision) floating-point number (see FLOAT for a single-precision floating-point number). Allowable values are: -1.7976931348623157E+308 to -2.2250738585072014E-308 0 2.2250738585072014E-308 to 1.7976931348623157E+308 These are the theoretical limits, based on the IEEE standard. The actual range might be slightly smaller depending on your hardware or operating system. M is the total number of digits and D is the number of digits following the decimal point. If M and D are omitted, values are stored to the limits allowed by the hardware. A double-precision floating-point number is accurate to approximately 15 decimal places. UNSIGNED, if specified, disallows negative values. ZEROFILL, if specified, pads the number with zeros, up to the total number of digits specified by M. REAL and DOUBLE PRECISION are synonyms, unless the REAL_AS_FLOAT SQL mode is enabled, in which case REAL is a synonym for FLOAT rather than DOUBLE. See Floating Point Accuracy for issues when using floating-point numbers. For more details on the attributes, see Numeric Data Type Overview. Examples -------- CREATE TABLE t1 (d DOUBLE(5,0) zerofill); INSERT INTO t1 VALUES (1),(2),(3),(4); SELECT * FROM t1; +-------+ | d | +-------+ | 00001 | | 00002 | | 00003 | | 00004 | +-------+ URL: https://mariadb.com/kb/en/double/https://mariadb.com/kb/en/double/  FLOATSyntax ------ FLOAT[(M,D)] [SIGNED | UNSIGNED | ZEROFILL] Description ----------- A small (single-precision) floating-point number (see DOUBLE for a regular-size floating point number). Allowable values are: -3.402823466E+38 to -1.175494351E-38 0 1.175494351E-38 to 3.402823466E+38. These are the theoretical limits, based on the IEEE standard. The actual range might be slightly smaller depending on your hardware or operating system. M is the total number of digits and D is the number of digits following the decimal point. If M and D are omitted, values are stored to the limits allowed by the hardware. A single-precision floating-point number is accurate to approximately 7 decimal places. UNSIGNED, if specified, disallows negative values. Using FLOAT might give you some unexpected problems because all calculations in MariaDB are done with double precision. See Floating Point Accuracy. For more details on the attributes, see Numeric Data Type Overview. URL: https://mariadb.com/kb/en/float/https://mariadb.com/kb/en/float/ )JSON Data TypeThe JSON alias was added in MariaDB 10.2.7. This was done to make it possible to use JSON columns in statement based replication from MySQL to MariaDB and to make it possible for MariaDB to read mysqldumps from MySQL. JSON is an alias for LONGTEXT introduced for compatibility reasons with MySQL's JSON data type. MariaDB implements this as a LONGTEXT rather, as the JSON data type contradicts the SQL standard, and MariaDB's benchmarks indicate that performance is at least equivalent. In order to ensure that a a valid json document is inserted, the JSON_VALID function can be used as a CHECK constraint. This constraint is automatically included for types using the JSON alias from MariaDB 10.4.3. Examples -------- CREATE TABLE t (j JSON); DESC t; +-------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+----------+------+-----+---------+-------+ | j | longtext | YES | | NULL | | +-------+----------+------+-----+---------+-------+ With validation: CREATE TABLE t2 ( j JSON CHECK (JSON_VALID(j)) ); INSERT INTO t2 VALUES ('invalid'); ERROR 4025 (23000): CONSTRAINT `j` failed for `test`.`t2` INSERT INTO t2 VALUES ('{"id": 1, "name": "Monty"}'); Query OK, 1 row affected (0.13 sec) Replicating JSON Data Between MySQL and MariaDB The JSON type in MySQL stores the JSON object in a compact form, not as LONGTEXT as in MariaDB. This means that row based replication will not work for JSON types from MySQL to MariaDB. There are a a few different ways to solve this: Use statement based replication. Change the JSON column to type TEXT in MySQL Converting a MySQL TABLE with JSON Fields to MariaDB MariaDB can't directly access MySQL's JSON format. There are a a few different ways to move the table to MariaDB: Change the JSON column to type TEXT in MySQL. After this, MariaDB can directly use the table without any need for a dump and restore. Use mysqldump to copy the table. Differences Between MySQL JSON Strings and MariaDB JSON Strings In MySQL, JSON is an object and is compared according to json values. In MariaDB JSON strings are normal strings and compared as strings. One exception is when using JSON_EXTRACT() in which case strings are unescaped before comparison. URL: https://mariadb.com/kb/en/json-data-type/https://mariadb.com/kb/en/json-data-type/,) ST_PolyFromWKBSyntax ------ ST_PolyFromWKB(wkb[,srid]) ST_PolygonFromWKB(wkb[,srid]) PolyFromWKB(wkb[,srid]) PolygonFromWKB(wkb[,srid]) Description ----------- Constructs a POLYGON value using its WKB representation and SRID. ST_PolyFromWKB(), ST_PolygonFromWKB(), PolyFromWKB() and PolygonFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(ST_PolyFromText('POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1))')); SELECT ST_AsText(ST_PolyFromWKB(@g)) AS p; +----------------------------------------+ | p | +----------------------------------------+ | POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1)) | +----------------------------------------+ URL: https://mariadb.com/kb/en/st_polyfromwkb/https://mariadb.com/kb/en/st_polyfromwkb/-a, ST_PolygonFromWKBA synonym for ST_PolyFromWKB. URL: https://mariadb.com/kb/en/st_polygonfromwkb/https://mariadb.com/kb/en/st_polygonfromwkb/.i7$BOUNDARYA synonym for ST_BOUNDARY. URL: https://mariadb.com/kb/en/geometry-properties-boundary/https://mariadb.com/kb/en/geometry-properties-boundary// W$$DIMENSIONA synonym for ST_DIMENSION. URL: https://mariadb.com/kb/en/dimension/https://mariadb.com/kb/en/dimension/0i7$ENVELOPEA synonym for ST_ENVELOPE. URL: https://mariadb.com/kb/en/geometry-properties-envelope/https://mariadb.com/kb/en/geometry-properties-envelope/1 k8$GeometryNA synonym for ST_GeometryN. URL: https://mariadb.com/kb/en/geometry-properties-geometryn/https://mariadb.com/kb/en/geometry-properties-geometryn/2 q;$GeometryTypeA synonym for ST_GeometryType. URL: https://mariadb.com/kb/en/geometry-properties-geometrytype/https://mariadb.com/kb/en/geometry-properties-geometrytype/3U#$IsClosedA synonym for ST_IsClosed. URL: https://mariadb.com/kb/en/isclosed/https://mariadb.com/kb/en/isclosed/4g6$IsEmptyA synonym for ST_IsEmpty. URL: https://mariadb.com/kb/en/geometry-properties-isempty/https://mariadb.com/kb/en/geometry-properties-isempty/5Q!$IsRingA synonym for ST_IsRing. URL: https://mariadb.com/kb/en/isring/https://mariadb.com/kb/en/isring/PJH U U> I/&)Geometry TypesDescription ----------- MariaDB provides a standard way of creating spatial columns for geometry types, for example, with CREATE TABLE or ALTER TABLE. Currently, spatial columns are supported for MyISAM, InnoDB, NDB, and ARCHIVE tables. See also SPATIAL INDEX. The basic geometry type is GEOMETRY. But the type can be more specific. The following types are supported: Geometry Types | POINT | LINESTRING | POLYGON | MULTIPOINT | MULTILINESTRING | MULTIPOLYGON | GEOMETRYCOLLECTION | GEOMETRY | Examples -------- Note: For clarity, only one type is listed per table in the examples below, but a table row can contain multiple types. For example: CREATE TABLE object (shapeA POLYGON, shapeB LINESTRING); POINT CREATE TABLE gis_point (g POINT); SHOW FIELDS FROM gis_point; INSERT INTO gis_point VALUES (PointFromText('POINT(10 10)')), (PointFromText('POINT(20 10)')), (PointFromText('POINT(20 20)')), (PointFromWKB(AsWKB(PointFromText('POINT(10 20)')))); LINESTRING CREATE TABLE gis_line (g LINESTRING); SHOW FIELDS FROM gis_line; INSERT INTO gis_line VALUES (LineFromText('LINESTRING(0 0,0 10,10 0)')), (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')), (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10))))); POLYGON CREATE TABLE gis_polygon (g POLYGON); SHOW FIELDS FROM gis_polygon; INSERT INTO gis_polygon VALUES (PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')), (PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))')), (PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0), Point(30, 0), Point(30, 30), Point(0, 0)))))); MULTIPOINT CREATE TABLE gis_multi_point (g MULTIPOINT); SHOW FIELDS FROM gis_multi_point; INSERT INTO gis_multi_point VALUES (MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20 20)')), (MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')), (MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4, 10))))); MULTILINESTRING CREATE TABLE gis_multi_line (g MULTILINESTRING); SHOW FIELDS FROM gis_multi_line; INSERT INTO gis_multi_line VALUES (MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')), (MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')), (MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2), Point(3, 5)), LineString(Point(2, 5), Point(5, 8), Point(21, 7)))))); MULTIPOLYGON CREATE TABLE gis_multi_polygon (g MULTIPOLYGON); SHOW FIELDS FROM gis_multi_polygon; INSERT INTO gis_multi_polygon VALUES (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')), (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')), (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3))))))); GEOMETRYCOLLECTION CREATE TABLE gis_geometrycollection (g GEOMETRYCOLLECTION); SHOW FIELDS FROM gis_geometrycollection; INSERT INTO gis_geometrycollection VALUES (GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0,10 10))')), (GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6), LineString(Point(3, 6), Point(7, 9)))))), (GeomFromText('GeometryCollection()')), (GeomFromText('GeometryCollection EMPTY')); GEOMETRY CREATE TABLE gis_geometry (g GEOMETRY); SHOW FIELDS FROM gis_geometry; INSERT into gis_geometry SELECT * FROM gis_point; INSERT into gis_geometry SELECT * FROM gis_line; INSERT into gis_geometry SELECT * FROM gis_polygon; INSERT into gis_geometry SELECT * FROM gis_multi_point; INSERT into gis_geometry SELECT * FROM gis_multi_line; INSERT into gis_geometry SELECT * FROM gis_multi_polygon; INSERT into gis_geometry SELECT * FROM gis_geometrycollection; URL: https://mariadb.com/kb/en/geometry-types/https://mariadb.com/kb/en/geometry-types/ a$MEDIUMINTSyntax ------ MEDIUMINT[(M)] [SIGNED | UNSIGNED | ZEROFILL] Description ----------- A medium-sized integer. The signed range is -8388608 to 8388607. The unsigned range is 0 to 16777215. ZEROFILL pads the integer with zeroes and assumes UNSIGNED (even if UNSIGNED is not specified). For details on the attributes, see Numeric Data Type Overview. Examples -------- CREATE TABLE mediumints (a MEDIUMINT,b MEDIUMINT UNSIGNED,c MEDIUMINT ZEROFILL); DESCRIBE mediumints; +-------+--------------------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+--------------------------------+------+-----+---------+-------+ | a | mediumint(9) | YES | | NULL | | | b | mediumint(8) unsigned | YES | | NULL | | | c | mediumint(8) unsigned zerofill | YES | | NULL | | +-------+--------------------------------+------+-----+---------+-------+ INSERT INTO mediumints VALUES (-10,-10,-10); Query OK, 1 row affected, 2 warnings (0.05 sec) Warning (Code 1264): Out of range value for column 'b' at row 1 Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO mediumints VALUES (-10,10,-10); Query OK, 1 row affected, 1 warning (0.08 sec) Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO mediumints VALUES (-10,10,10); INSERT INTO mediumints VALUES (8388608,8388608,8388608); Query OK, 1 row affected, 1 warning (0.05 sec) Warning (Code 1264): Out of range value for column 'a' at row 1 INSERT INTO mediumints VALUES (8388607,8388608,8388608); SELECT * FROM mediumints; +---------+---------+----------+ | a | b | c | +---------+---------+----------+ | -10 | 0 | 00000000 | | -10 | 0 | 00000000 | | -10 | 10 | 00000000 | | -10 | 10 | 00000010 | | 8388607 | 8388608 | 08388608 | | 8388607 | 8388608 | 08388608 | +---------+---------+----------+ URL: https://mariadb.com/kb/en/mediumint/https://mariadb.com/kb/en/mediumint/6i7$IsSimpleA synonym for ST_IsSImple. URL: https://mariadb.com/kb/en/geometry-properties-issimple/https://mariadb.com/kb/en/geometry-properties-issimple/7 s<$NumGeometriesA synonym for ST_NumGeometries. URL: https://mariadb.com/kb/en/geometry-properties-numgeometries/https://mariadb.com/kb/en/geometry-properties-numgeometries/8a3$SRIDA synonym for ST_SRID. URL: https://mariadb.com/kb/en/geometry-properties-srid/https://mariadb.com/kb/en/geometry-properties-srid/: '$ST_DIMENSIONSyntax ------ ST_Dimension(g) Dimension(g) Description ----------- Returns the inherent dimension of the geometry value g. The result can be Dimension | Definition | -1 | empty geometry | 0 | geometry with no length or area | 1 | geometry with no area but nonzero length | 2 | geometry with nonzero area | ST_Dimension() and Dimension() are synonyms. Examples -------- SELECT Dimension(GeomFromText('LineString(1 1,2 2)')); +------------------------------------------------+ | Dimension(GeomFromText('LineString(1 1,2 2)')) | +------------------------------------------------+ | 1 | +------------------------------------------------+ URL: https://mariadb.com/kb/en/st_dimension/https://mariadb.com/kb/en/st_dimension/< X'$ST_GEOMETRYNSyntax ------ ST_GeometryN(gc,N) GeometryN(gc,N) Description ----------- Returns the N-th geometry in the GeometryCollection gc. Geometries are numbered beginning with 1. ST_GeometryN() and GeometryN() are synonyms. Example SET @gc = 'GeometryCollection(Point(1 1),LineString(12 14, 9 11))'; SELECT AsText(GeometryN(GeomFromText(@gc),1)); +----------------------------------------+ | AsText(GeometryN(GeomFromText(@gc),1)) | +----------------------------------------+ | POINT(1 1) | +----------------------------------------+ URL: https://mariadb.com/kb/en/st_geometryn/https://mariadb.com/kb/en/st_geometryn/N9w k/2q5Numeric Data Type OverviewThere are a number of numeric data types: TINYINT BOOLEAN - Synonym for TINYINT(1) SMALLINT MEDIUMINT INT, INTEGER BIGINT DECIMAL, DEC, NUMERIC, FIXED FLOAT DOUBLE, DOUBLE PRECISION, REAL BIT See the specific articles for detailed information on each. SIGNED, UNSIGNED and ZEROFILL Most numeric types can be defined as SIGNED, UNSIGNED or ZEROFILL, for example: TINYINT[(M)] [SIGNED | UNSIGNED | ZEROFILL] If SIGNED, or no attribute, is specified, a portion of the numeric type will be reserved for the sign (plus or minus). For example, a TINYINT SIGNED can range from -128 to 127. If UNSIGNED is specified, no portion of the numeric type is reserved for the sign, so for integer types range can be larger. For example, a TINYINT UNSIGNED can range from 0 to 255. Floating point and fixed-point types also can be UNSIGNED, but this only prevents negative values from being stored and doesn't alter the range. If ZEROFILL is specified, the column will be set to UNSIGNED and the spaces used by default to pad the field are replaced with zeros. ZEROFILL is ignored in expressions or as part of a UNION. ZEROFILL is a non-standard MySQL and MariaDB enhancement. Note that although the preferred syntax indicates that the attributes are exclusive, more than one attribute can be specified. Until MariaDB 10.2.7 (MDEV-8659), any combination of the attributes could be used in any order, with duplicates. In this case: the presence of ZEROFILL makes the column UNSIGNED ZEROFILL. the presence of UNSIGNED makes the column UNSIGNED. From MariaDB 10.2.8, only the following combinations are supported: SIGNED UNSIGNED ZEROFILL UNSIGNED ZEROFILL ZEROFILL UNSIGNED The latter two should be replaced with simply ZEROFILL, but are still accepted by the parser. Examples -------- CREATE TABLE zf ( i1 TINYINT SIGNED, i2 TINYINT UNSIGNED, i3 TINYINT ZEROFILL ); INSERT INTO zf VALUES (2,2,2); SELECT * FROM zf; +------+------+------+ | i1 | i2 | i3 | +------+------+------+ | 2 | 2 | 002 | +------+------+------+ Range When attempting to add a value that is out of the valid range for the numeric type, MariaDB will react depending on the strict SQL_MODE setting. If strict_mode has been set (the default from MariaDB 10.2.4), MariaDB will return an error. If strict_mode has not been set (the default until MariaDB 10.2.3), MariaDB will adjust the number to fit in the field, returning a warning. Examples -------- With strict_mode set: SHOW VARIABLES LIKE 'sql_mode'; +---------------+-------------------------------------------------------------------------------------------+ | Variable_name | Value | +---------------+-------------------------------------------------------------------------------------------+ | sql_mode | STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +---------------+-------------------------------------------------------------------------------------------+ CREATE TABLE ranges (i1 TINYINT, i2 SMALLINT, i3 TINYINT UNSIGNED); INSERT INTO ranges VALUES (257,257,257); ERROR 1264 (22003): Out of range value for column 'i1' at row 1 SELECT * FROM ranges; Empty set (0.10 sec) With strict_mode unset: SHOW VARIABLES LIKE 'sql_mode%'; +---------------+-------+ | Variable_name | Value | +---------------+-------+ | sql_mode | | +---------------+-------+ CREATE TABLE ranges (i1 TINYINT, i2 SMALLINT, i3 TINYINT UNSIGNED); INSERT INTO ranges VALUES (257,257,257); Query OK, 1 row affected, 2 warnings (0.00 sec) SHOW WARNINGS; +---------+------+---------------------------------------------+ | Level | Code | Message | +---------+------+---------------------------------------------+ | Warning | 1264 | Out of range value for column 'i1' at row 1 | | Warning | 1264 | Out of range value for column 'i3' at row 1 | +---------+------+---------------------------------------------+ 2 rows in set (0.00 sec) SELECT * FROM ranges; +------+------+------+ | i1 | i2 | i3 | +------+------+------+ | 127 | 257 | 255 | +------+------+------+ Auto_increment The AUTO_INCREMENT attribute can be used to generate a unique identity for new rows. For more details, see auto_increment. URL: https://mariadb.com/kb/en/numeric-data-type-overview/https://mariadb.com/kb/en/numeric-data-type-overview/!#SMALLINTSyntax ------ SMALLINT[(M)] [SIGNED | UNSIGNED | ZEROFILL] Description ----------- A small integer. The signed range is -32768 to 32767. The unsigned range is 0 to 65535. If a column has been set to ZEROFILL, all values will be prepended by zeros so that the SMALLINT value contains a number of M digits. Note: If the ZEROFILL attribute has been specified, the column will automatically become UNSIGNED. For more details on the attributes, see Numeric Data Type Overview. Examples -------- CREATE TABLE smallints (a SMALLINT,b SMALLINT UNSIGNED,c SMALLINT ZEROFILL); INSERT INTO smallints VALUES (-10,-10,-10); Query OK, 1 row affected, 2 warnings (0.09 sec) Warning (Code 1264): Out of range value for column 'b' at row 1 Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO smallints VALUES (-10,10,-10); Query OK, 1 row affected, 1 warning (0.08 sec) Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO smallints VALUES (-10,10,10); INSERT INTO smallints VALUES (32768,32768,32768); Query OK, 1 row affected, 1 warning (0.04 sec) Warning (Code 1264): Out of range value for column 'a' at row 1 INSERT INTO smallints VALUES (32767,32768,32768); SELECT * FROM smallints; +-------+-------+-------+ | a | b | c | +-------+-------+-------+ | -10 | 0 | 00000 | | -10 | 10 | 00000 | | -10 | 10 | 00010 | | 32767 | 32768 | 32768 | | 32767 | 32768 | 32768 | +-------+-------+-------+ URL: https://mariadb.com/kb/en/smallint/https://mariadb.com/kb/en/smallint/=l*$ST_GEOMETRYTYPESyntax ------ ST_GeometryType(g) GeometryType(g) Description ----------- Returns as a string the name of the geometry type of which the geometry instance g is a member. The name corresponds to one of the instantiable Geometry subclasses. ST_GeometryType() and GeometryType() are synonyms. Examples -------- SELECT GeometryType(GeomFromText('POINT(1 1)')); +------------------------------------------+ | GeometryType(GeomFromText('POINT(1 1)')) | +------------------------------------------+ | POINT | +------------------------------------------+ URL: https://mariadb.com/kb/en/st_geometrytype/https://mariadb.com/kb/en/st_geometrytype/? %$ST_ISEMPTYSyntax ------ ST_IsEmpty(g) IsEmpty(g) Description ----------- IsEmpty is a function defined by the OpenGIS specification, but is not fully implemented by MariaDB or MySQL. Since MariaDB and MySQL do not support GIS EMPTY values such as POINT EMPTY, as implemented it simply returns 1 if the geometry value g is invalid, 0 if it is valid, and NULL if the argument is NULL. ST_IsEmpty() and IsEmpty() are synonyms. URL: https://mariadb.com/kb/en/st_isempty/https://mariadb.com/kb/en/st_isempty/@ $$ST_IsRingThe ST_IsRing function was introduced in MariaDB 10.1.2 Syntax ------ ST_IsRing(g) IsRing(g) Description ----------- Returns true if a given LINESTRING is a ring, that is, both ST_IsClosed and ST_IsSimple. A simple curve does not pass through the same point more than once. However, see MDEV-7510. St_IsRing() and IsRing() are synonyms. URL: https://mariadb.com/kb/en/st_isring/https://mariadb.com/kb/en/st_isring/ 2# X" *String LiteralsStrings are sequences of characters and are enclosed with quotes. The syntax is: [_charset_name]'string' [COLLATE collation_name] For example: 'The MariaDB Foundation' _utf8 'Foundation' COLLATE utf8_unicode_ci; Strings can either be enclosed in single quotes or in double quotes (the same character must be used to both open and close the string). The ANSI SQL-standard does not permit double quotes for enclosing strings, and although MariaDB does by default, if the MariaDB server has enabled the ANSI_QUOTES_SQL SQL_MODE, double quotes will be treated as being used for identifiers instead of strings. Strings that are next to each other are automatically concatenated. For example: 'The ' 'MariaDB ' 'Foundation' and 'The MariaDB Foundation' are equivalent. The \ (backslash character) is used to escape characters. For example: 'MariaDB's new features' is not a valid string because of the single quote in the middle of the string, which is treated as if it closes the string, but is actually meant as part of the string, an apostrophe. The backslash character helps in situations like this: 'MariaDB\'s new features' is now a valid string, and if displayed, will appear without the backslash. SELECT 'MariaDB\'s new features'; +------------------------+ | MariaDB's new features | +------------------------+ | MariaDB's new features | +------------------------+ Another way to escape the quoting character is repeating it twice: SELECT 'I''m here', """Double"""; +----------+----------+ | I'm here | "Double" | +----------+----------+ | I'm here | "Double" | +----------+----------+ Escape sequences There are other escape sequences also. Here is a full list: Escape sequence | Character | \0 | ASCII NUL (0x00). | \' | Single quote (“'”). | \" | Double quote (“"”). | \b | Backspace. | \n | Newline, or linefeed,. | \r | Carriage return. | \t | Tab. | \Z | ASCII 26 (Control+Z). See note following the table. | \\ | Backslash (“\”). | \% | “%” character. See note following the table. | \_ | A “_” character. See note following the table. | Escaping the % and _ characters can be necessary when using the LIKE operator, which treats them as special characters. The ASCII 26 character (\Z) needs to be escaped when included in a batch file which needs to be executed in Windows. The reason is that ASCII 26, in Windows, is the end of file (EOF). Backslash (\), if not used as an escape character, must always be escaped. When followed by a character that is not in the above table, backslashes will simply be ignored. URL: https://mariadb.com/kb/en/string-literals/https://mariadb.com/kb/en/string-literals/# TEXTSyntax ------ TEXT[(M)] [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- A TEXT column with a maximum length of 65,535 (216 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. Each TEXT value is stored using a two-byte length prefix that indicates the number of bytes in the value. If you need a bigger storage, consider using MEDIUMTEXT instead. An optional length M can be given for this type. If this is done, MariaDB creates the column as the smallest TEXT type large enough to hold values M characters long. Before MariaDB 10.2, all MariaDB collations were of type PADSPACE, meaning that TEXT (as well as VARCHAR and CHAR values) are compared without regard for trailing spaces. This does not apply to the LIKE pattern-matching operator, which takes into account trailing spaces. Before MariaDB 10.2.1, BLOB and TEXT columns could not be assigned a DEFAULT value. This restriction was lifted in MariaDB 10.2.1. Examples -------- Trailing spaces: CREATE TABLE strtest (d TEXT(10)); INSERT INTO strtest VALUES('Maria '); SELECT d='Maria',d='Maria ' FROM strtest; +-----------+--------------+ | d='Maria' | d='Maria ' | +-----------+--------------+ | 1 | 1 | +-----------+--------------+ SELECT d LIKE 'Maria',d LIKE 'Maria ' FROM strtest; +----------------+-------------------+ | d LIKE 'Maria' | d LIKE 'Maria ' | +----------------+-------------------+ | 0 | 1 | +----------------+-------------------+ Difference between VARCHAR and TEXT VARCHAR columns can be fully indexed. TEXT columns can only be indexed over a specified length. Using TEXT or BLOB in a SELECT query that uses temporary tables for storing intermediate results will force the temporary table to be disk based (using the Aria storage engine instead of the memory storage engine, which is a bit slower. This is not that bad as the Aria storage engine caches the rows in memory. To get the benefit of this, one should ensure that the aria_pagecache_buffer_size variable is big enough to hold most of the row and index data for temporary tables. For Storage Engine Developers Internally the full length of the VARCHAR column is allocated inside each TABLE objects record[] structure. As there are three such buffers, each open table will allocate 3 times max-length-to-store-varchar bytes of memory. TEXT and BLOB columns are stored with a pointer (4 or 8 bytes) + a 1-4 bytes length. The TEXT data is only stored once. This means that internally TEXT uses less memory for each open table but instead has the additional overhead that each TEXT object needs to be allocated and freed for each row access (with some caching in between). URL: https://mariadb.com/kb/en/text/https://mariadb.com/kb/en/text/A $&$ST_IsSimpleSyntax ------ ST_IsSimple(g) IsSimple(g) Description ----------- Returns true if the given Geometry has no anomalous geometric points, false if it does, or NULL if given a NULL value. ST_IsSimple() and IsSimple() are synonyms. Examples -------- A POINT is always simple. SET @g = 'Point(1 2)'; SELECT ST_ISSIMPLE(GEOMFROMTEXT(@g)); +-------------------------------+ | ST_ISSIMPLE(GEOMFROMTEXT(@g)) | +-------------------------------+ | 1 | +-------------------------------+ URL: https://mariadb.com/kb/en/st_issimple/https://mariadb.com/kb/en/st_issimple/B+$ST_NUMGEOMETRIESSyntax ------ ST_NumGeometries(gc) NumGeometries(gc) Description ----------- Returns the number of geometries in the GeometryCollection gc. ST_NumGeometries() and NumGeometries() are synonyms. Example SET @gc = 'GeometryCollection(Point(1 1),LineString(2 2, 3 3))'; SELECT NUMGEOMETRIES(GeomFromText(@gc)); +----------------------------------+ | NUMGEOMETRIES(GeomFromText(@gc)) | +----------------------------------+ | 2 | +----------------------------------+ URL: https://mariadb.com/kb/en/st_numgeometries/https://mariadb.com/kb/en/st_numgeometries/C $$ST_RELATEThe ST_RELATE() function was introduced in MariaDB 10.1.2 Syntax ------ ST_Relate(g1, g2, i) Description ----------- Returns true if Geometry g1 is spatially related to Geometryg2 by testing for intersections between the interior, boundary and exterior of the two geometries as specified by the values in intersection matrix pattern i. URL: https://mariadb.com/kb/en/st_relate/https://mariadb.com/kb/en/st_relate/D"$ST_SRIDSyntax ------ ST_SRID(g) SRID(g) Description ----------- Returns an integer indicating the Spatial Reference System ID for the geometry value g. In MariaDB, the SRID value is just an integer associated with the geometry value. All calculations are done assuming Euclidean (planar) geometry. ST_SRID() and SRID() are synonyms. Examples -------- SELECT SRID(GeomFromText('LineString(1 1,2 2)',101)); +-----------------------------------------------+ | SRID(GeomFromText('LineString(1 1,2 2)',101)) | +-----------------------------------------------+ | 101 | +-----------------------------------------------+ URL: https://mariadb.com/kb/en/st_srid/https://mariadb.com/kb/en/st_srid/Y)dc 0>$ TIMESyntax ------ TIME [()] Description ----------- A time. The range is '-838:59:59.999999' to '838:59:59.999999'. Microsecond precision can be from 0-6; if not specified 0 is used. Microseconds have been available since MariaDB 5.3. MariaDB displays TIME values in 'HH:MM:SS.ssssss' format, but allows assignment of times in looser formats, including 'D HH:MM:SS', 'HH:MM:SS', 'HH:MM', 'D HH:MM', 'D HH', 'SS', or 'HHMMSS', as well as permitting dropping of any leading zeros when a delimiter is provided, for example '3:9:10'. For details, see date and time literals. MariaDB 10.1.2 introduced the --mysql56-temporal-format option, on by default, which allows MariaDB to store TIMEs using the same low-level format MySQL 5.6 uses. Internal Format In MariaDB 10.1.2 a new temporal format was introduced from MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP columns operate at lower levels. These changes allow these temporal data types to have fractional parts and negative values. You can disable this feature using the mysql56_temporal_format system variable. Tables that include TIMESTAMP values that were created on an older version of MariaDB or that were created while the mysql56_temporal_format system variable was disabled continue to store data using the older data type format. In order to update table columns from the older format to the newer format, execute an ALTER TABLE... MODIFY COLUMN statement that changes the column to the *same* data type. This change may be needed if you want to export the table's tablespace and import it onto a server that has mysql56_temporal_format=ON set (see MDEV-15225). For instance, if you have a TIME column in your table: SHOW VARIABLES LIKE 'mysql56_temporal_format'; +-------------------------+-------+ | Variable_name | Value | +-------------------------+-------+ | mysql56_temporal_format | ON | +-------------------------+-------+ ALTER TABLE example_table MODIFY ts_col TIME; When MariaDB executes the ALTER TABLE statement, it converts the data from the older temporal format to the newer one. In the event that you have several tables and columns using temporal data types that you want to switch over to the new format, make sure the system variable is enabled, then perform a dump and restore using mysqldump. The columns using relevant temporal data types are restored using the new temporal format. Examples -------- INSERT INTO time VALUES ('90:00:00'), ('800:00:00'), (800), (22), (151413), ('9:6:3'), ('12 09'); SELECT * FROM time; +-----------+ | t | +-----------+ | 90:00:00 | | 800:00:00 | | 00:08:00 | | 00:00:22 | | 15:14:13 | | 09:06:03 | | 297:00:00 | +-----------+ URL: https://mariadb.com/kb/en/time/https://mariadb.com/kb/en/time/'x"TINYINTSyntax ------ TINYINT[(M)] [SIGNED | UNSIGNED | ZEROFILL] Description ----------- A very small integer. The signed range is -128 to 127. The unsigned range is 0 to 255. For details on the attributes, see Numeric Data Type Overview. Examples -------- CREATE TABLE tinyints (a TINYINT,b TINYINT UNSIGNED,c TINYINT ZEROFILL); Query OK, 0 rows affected (0.43 sec) INSERT INTO tinyints VALUES (-10,-10,-10); Query OK, 1 row affected, 2 warnings (0.08 sec) Warning (Code 1264): Out of range value for column 'b' at row 1 Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO tinyints VALUES (-10,10,-10); Query OK, 1 row affected, 1 warning (0.11 sec) Warning (Code 1264): Out of range value for column 'c' at row 1 INSERT INTO tinyints VALUES (-10,10,10); SELECT * FROM tinyints; +------+------+------+ | a | b | c | +------+------+------+ | -10 | 0 | 000 | | -10 | 10 | 000 | | -10 | 10 | 010 | +------+------+------+ INSERT INTO tinyints VALUES (128,128,128); Query OK, 1 row affected, 1 warning (0.19 sec) Warning (Code 1264): Out of range value for column 'a' at row 1 INSERT INTO tinyints VALUES (127,128,128); SELECT * FROM tinyints; +------+------+------+ | a | b | c | +------+------+------+ | -10 | 0 | 000 | | -10 | 10 | 000 | | -10 | 10 | 010 | | 127 | 128 | 128 | | 127 | 128 | 128 | +------+------+------+ URL: https://mariadb.com/kb/en/tinyint/https://mariadb.com/kb/en/tinyint/) $VARBINARYSyntax ------ VARBINARY(M) Description ----------- The VARBINARY type is similar to the VARCHAR type, but stores binary byte strings rather than non-binary character strings. M represents the maximum column length in bytes. It contains no character set, and comparison and sorting are based on the numeric value of the bytes. If the maximum length is exceeded, and SQL strict mode is not enabled , the extra characters will be dropped with a warning. If strict mode is enabled, an error will occur. Unlike BINARY values, VARBINARYs are not right-padded when inserting. Oracle Mode In Oracle mode from MariaDB 10.3, RAW is a synonym for VARBINARY. Examples -------- Inserting too many characters, first with strict mode off, then with it on: CREATE TABLE varbins (a VARBINARY(10)); INSERT INTO varbins VALUES('12345678901'); Query OK, 1 row affected, 1 warning (0.04 sec) SELECT * FROM varbins; +------------+ | a | +------------+ | 1234567890 | +------------+ SET sql_mode='STRICT_ALL_TABLES'; INSERT INTO varbins VALUES('12345678901'); ERROR 1406 (22001): Data too long for column 'a' at row 1 Sorting is performed with the byte value: TRUNCATE varbins; INSERT INTO varbins VALUES('A'),('B'),('a'),('b'); SELECT * FROM varbins ORDER BY a; +------+ | a | +------+ | A | | B | | a | | b | +------+ Using CAST to sort as a CHAR instead: SELECT * FROM varbins ORDER BY CAST(a AS CHAR); +------+ | a | +------+ | a | | A | | b | | B | +------+ URL: https://mariadb.com/kb/en/varbinary/https://mariadb.com/kb/en/varbinary/E> %ASCIISyntax ------ ASCII(str) Description ----------- Returns the numeric ASCII value of the leftmost character of the string argument. Returns 0 if the given string is empty and NULL if it is NULL. ASCII() works for 8-bit characters. Examples -------- SELECT ASCII(9); +----------+ | ASCII(9) | +----------+ | 57 | +----------+ SELECT ASCII('9'); +------------+ | ASCII('9') | +------------+ | 57 | +------------+ SELECT ASCII('abc'); +--------------+ | ASCII('abc') | +--------------+ | 97 | +--------------+ URL: https://mariadb.com/kb/en/ascii/https://mariadb.com/kb/en/ascii/F%BINSyntax ------ BIN(N) Description ----------- Returns a string representation of the binary value of the given longlong (that is, BIGINT) number. This is equivalent to CONV(N,10,2). The argument should be positive. If it is a FLOAT, it will be truncated. Returns NULL if the argument is NULL. Examples -------- SELECT BIN(12); +---------+ | BIN(12) | +---------+ | 1100 | +---------+ URL: https://mariadb.com/kb/en/bin/https://mariadb.com/kb/en/bin/H V%%BIT_LENGTHSyntax ------ BIT_LENGTH(str) Description ----------- Returns the length of the given string argument in bits. If the argument is not a string, it will be converted to string. If the argument is NULL, it returns NULL. Examples -------- SELECT BIT_LENGTH('text'); +--------------------+ | BIT_LENGTH('text') | +--------------------+ | 32 | +--------------------+ SELECT BIT_LENGTH(''); +----------------+ | BIT_LENGTH('') | +----------------+ | 0 | +----------------+ Compatibility PostgreSQL and Sybase support BIT_LENGTH(). URL: https://mariadb.com/kb/en/bit_length/https://mariadb.com/kb/en/bit_length/7q4  _N*"VARCHARSyntax ------ [NATIONAL] VARCHAR(M) [CHARACTER SET charset_name] [COLLATE collation_name] Description ----------- A variable-length string. M represents the maximum column length in characters. The range of M is 0 to 65,532. The effective maximum length of a VARCHAR is subject to the maximum row size and the character set used. For example, utf8 characters can require up to three bytes per character, so a VARCHAR column that uses the utf8 character set can be declared to be a maximum of 21,844 characters. MariaDB stores VARCHAR values as a one-byte or two-byte length prefix plus data. The length prefix indicates the number of bytes in the value. A VARCHAR column uses one length byte if values require no more than 255 bytes, two length bytes if values may require more than 255 bytes. Note: MariaDB 5.1 and later follow the standard SQL specification, and do not remove trailing spaces from VARCHAR values. VARCHAR(0) columns can contain 2 values: an empty string or NULL. Such columns cannot be part of an index. The CONNECT storage engine does not support VARCHAR(0). VARCHAR is shorthand for CHARACTER VARYING. NATIONAL VARCHAR is the standard SQL way to define that a VARCHAR column should use some predefined character set. MariaDB uses utf8 as this predefined character set, as does MySQL 4.1 and up. NVARCHAR is shorthand for NATIONAL VARCHAR. Before MariaDB 10.2, all MariaDB collations were of type PADSPACE, meaning that VARCHAR (as well as CHAR and TEXT values) are compared without regard for trailing spaces. This does not apply to the LIKE pattern-matching operator, which takes into account trailing spaces. From MariaDB 10.2, a number of NO PAD collations are available. If a unique index consists of a column where trailing pad characters are stripped or ignored, inserts into that column where values differ only by the number of trailing pad characters will result in a duplicate-key error. Examples -------- The following are equivalent: VARCHAR(30) CHARACTER SET utf8 NATIONAL VARCHAR(30) NVARCHAR(30) NCHAR VARCHAR(30) NATIONAL CHARACTER VARYING(30) NATIONAL CHAR VARYING(30) Trailing spaces: CREATE TABLE strtest (v VARCHAR(10)); INSERT INTO strtest VALUES('Maria '); SELECT v='Maria',v='Maria ' FROM strtest; +-----------+--------------+ | v='Maria' | v='Maria ' | +-----------+--------------+ | 1 | 1 | +-----------+--------------+ SELECT v LIKE 'Maria',v LIKE 'Maria ' FROM strtest; +----------------+-------------------+ | v LIKE 'Maria' | v LIKE 'Maria ' | +----------------+-------------------+ | 0 | 1 | +----------------+-------------------+ Truncation Depending on whether or not strict sql mode is set, you will either get a warning or an error if you try to insert a string that is too long into a VARCHAR column. If the extra characters are spaces, the spaces that can't fit will be removed and you will always get a warning, regardless of the sql mode setting. Difference Between VARCHAR and TEXT VARCHAR columns can be fully indexed. TEXT columns can only be indexed over a specified length. Using TEXT or BLOB in a SELECT query that uses temporary tables for storing intermediate results will force the temporary table to be disk based (using the Aria storage engine instead of the memory storage engine, which is a bit slower. This is not that bad as the Aria storage engine caches the rows in memory. To get the benefit of this, one should ensure that the aria_pagecache_buffer_size variable is big enough to hold most of the row and index data for temporary tables. Oracle Mode In Oracle mode from MariaDB 10.3, VARCHAR2 is a synonym. For Storage Engine Developers Internally the full length of the VARCHAR column is allocated inside each TABLE objects record[] structure. As there are three such buffers, each open table will allocate 3 times max-length-to-store-varchar bytes of memory. TEXT and BLOB columns are stored with a pointer (4 or 8 bytes) + a 1-4 bytes length. The TEXT data is only stored once. This means that internally TEXT uses less memory for each open table but instead has the additional overhead that each TEXT object needs to be allocated and freed for each row access (with some caching in between). URL: https://mariadb.com/kb/en/varchar/https://mariadb.com/kb/en/varchar/+ )YEAR Data TypeSyntax ------ YEAR[(4)] Description ----------- A year in two-digit or four-digit format. The default is four-digit format. Note that the two-digit format has been deprecated since 5.5.27. In four-digit format, the allowable values are 1901 to 2155, and 0000. In two-digit format, the allowable values are 70 to 69, representing years from 1970 to 2069. MariaDB displays YEAR values in YYYY format, but allows you to assign values to YEAR columns using either strings or numbers. Inserting numeric zero has a different result for YEAR(4) and YEAR(2). For YEAR(2), the value 00 reflects the year 2000. For YEAR(4), the value 0000 reflects the year zero. This only applies to numeric zero. String zero always reflects the year 2000. Examples -------- Accepting a string or a number: CREATE TABLE y(y YEAR); INSERT INTO y VALUES (1990),('2012'); SELECT * FROM y; +------+ | y | +------+ | 1990 | | 2012 | +------+ Out of range: INSERT INTO y VALUES (1005),('3080'); Query OK, 2 rows affected, 2 warnings (0.05 sec) Records: 2 Duplicates: 0 Warnings: 2 SHOW WARNINGS; +---------+------+--------------------------------------------+ | Level | Code | Message | +---------+------+--------------------------------------------+ | Warning | 1264 | Out of range value for column 'y' at row 1 | | Warning | 1264 | Out of range value for column 'y' at row 2 | +---------+------+--------------------------------------------+ SELECT * FROM y; +------+ | y | +------+ | 1990 | | 2012 | | 0000 | | 0000 | +------+ Truncating: INSERT INTO y VALUES ('2013-12-12'); Query OK, 1 row affected, 1 warning (0.05 sec) SHOW WARNINGS; +---------+------+----------------------------------------+ | Level | Code | Message | +---------+------+----------------------------------------+ | Warning | 1265 | Data truncated for column 'y' at row 1 | +---------+------+----------------------------------------+ SELECT * FROM y; +------+ | y | +------+ | 1990 | | 2012 | | 0000 | | 0000 | | 2013 | +------+ Difference between YEAR(2) and YEAR(4), and string and numeric zero: CREATE TABLE y2(y YEAR(4), y2 YEAR(2)); Query OK, 0 rows affected, 1 warning (0.40 sec) Note (Code 1287): 'YEAR(2)' is deprecated and will be removed in a future release. Please use YEAR(4) instead INSERT INTO y2 VALUES(0,0),('0','0'); SELECT YEAR(y),YEAR(y2) FROM y; +---------+----------+ | YEAR(y) | YEAR(y2) | +---------+----------+ | 0 | 2000 | | 2000 | 2000 | +---------+----------+ URL: https://mariadb.com/kb/en/year-data-type/https://mariadb.com/kb/en/year-data-type/K+%CHARACTER_LENGTHSyntax ------ CHARACTER_LENGTH(str) Description ----------- CHARACTER_LENGTH() is a synonym for CHAR_LENGTH(). URL: https://mariadb.com/kb/en/character_length/https://mariadb.com/kb/en/character_length/Z %INSTRSyntax ------ INSTR(str,substr) Description ----------- Returns the position of the first occurrence of substring substr in string str. This is the same as the two-argument form of LOCATE(), except that the order of the arguments is reversed. INSTR() performs a case-insensitive search. If any argument is NULL, returns NULL. Examples -------- SELECT INSTR('foobarbar', 'bar'); +---------------------------+ | INSTR('foobarbar', 'bar') | +---------------------------+ | 4 | +---------------------------+ SELECT INSTR('My', 'Maria'); +----------------------+ | INSTR('My', 'Maria') | +----------------------+ | 0 | +----------------------+ URL: https://mariadb.com/kb/en/instr/https://mariadb.com/kb/en/instr/  1H, 9 $BEGIN ENDSyntax ------ [begin_label:] BEGIN [NOT ATOMIC] [statement_list] END [end_label] NOT ATOMIC is required when used outside of a stored procedure. Inside stored procedures or within an anonymous block, BEGIN alone starts a new anonymous block. Description ----------- BEGIN ... END syntax is used for writing compound statements. A compound statement can contain multiple statements, enclosed by the BEGIN and END keywords. statement_list represents a list of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter. statement_list is optional, which means that the empty compound statement (BEGIN END) is legal. Note that END will perform a commit. If you are running in autocommit mode, every statement will be committed separately. If you are not running in autocommit mode, you must execute a COMMIT or ROLLBACK after END to get the database up to date. Use of multiple statements requires that a client is able to send statement strings containing the ; statement delimiter. This is handled in the mysql command-line client with the DELIMITER command. Changing the ; end-of-statement delimiter (for example, to //) allows ; to be used in a program body. A compound statement within a stored program can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same. BEGIN ... END constructs can be nested. Each block can define its own variables, a CONDITION, a HANDLER and a CURSOR, which don't exist in the outer blocks. The most local declarations override the outer objects which use the same name (see example below). The declarations order is the following: DECLARE local variables; DECLARE CONDITIONs; DECLARE CURSORs; DECLARE HANDLERs; Note that DECLARE HANDLER contains another BEGIN ... END construct. Here is an example of a very simple, anonymous block: BEGIN NOT ATOMIC SET @a=1; CREATE TABLE test.t1(a INT); END| Below is an example of nested blocks in a stored procedure: CREATE PROCEDURE t( ) BEGIN DECLARE x TINYINT UNSIGNED DEFAULT 1; BEGIN DECLARE x CHAR(2) DEFAULT '02'; DECLARE y TINYINT UNSIGNED DEFAULT 10; SELECT x, y; END; SELECT x; END; In this example, a TINYINT variable, x is declared in the outter block. But in the inner block x is re-declared as a CHAR and an y variable is declared. The inner SELECT shows the "new" value of x, and the value of y. But when x is selected in the outer block, the "old" value is returned. The final SELECT doesn't try to read y, because it doesn't exist in that context. URL: https://mariadb.com/kb/en/begin-end/https://mariadb.com/kb/en/begin-end/-)CASE StatementSyntax ------ CASE case_value WHEN when_value THEN statement_list [WHEN when_value THEN statement_list] ... [ELSE statement_list] END CASE Or: CASE WHEN search_condition THEN statement_list [WHEN search_condition THEN statement_list] ... [ELSE statement_list] END CASE Description ----------- The CASE statement for stored programs implements a complex conditional construct. If a search_condition evaluates to true, the corresponding SQL statement list is executed. If no search condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements. If no when_value or search_condition matches the value tested and the CASE statement contains no ELSE clause, a Case not found for CASE statement error results. Each statement_list consists of one or more statements; an empty statement_list is not allowed. To handle situations where no value is matched by any WHEN clause, use an ELSE containing an empty BEGIN ... END block, as shown in this example: DELIMITER | CREATE PROCEDURE p() BEGIN DECLARE v INT DEFAULT 1; CASE v WHEN 2 THEN SELECT v; WHEN 3 THEN SELECT 0; ELSE BEGIN END; END CASE; END; | The indentation used here in the ELSE clause is for purposes of clarity only, and is not otherwise significant. See Delimiters in the mysql client for more on the use of the delimiter command. Note: The syntax of the CASE statement used inside stored programs differs slightly from that of the SQL CASE expression described in CASE OPERATOR. The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END. URL: https://mariadb.com/kb/en/case-statement/https://mariadb.com/kb/en/case-statement//^,DECLARE CONDITIONSyntax ------ DECLARE condition_name CONDITION FOR condition_value condition_value: SQLSTATE [VALUE] sqlstate_value | mysql_error_code Description ----------- The DECLARE ... CONDITION statement defines a named error condition. It specifies a condition that needs specific handling and associates a name with that condition. Later, the name can be used in a DECLARE ... HANDLER, SIGNAL or RESIGNAL statement (as long as the statement is located in the same BEGIN ... END block). Conditions must be declared after local variables, but before CURSORs and HANDLERs. A condition_value for DECLARE ... CONDITION can be an SQLSTATE value (a 5-character string literal) or a MySQL error code (a number). You should not use SQLSTATE value '00000' or MySQL error code 0, because those indicate sucess rather than an error condition. If you try, or if you specify an invalid SQLSTATE value, an error like this is produced: ERROR 1407 (42000): Bad SQLSTATE: '00000' For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes. URL: https://mariadb.com/kb/en/declare-condition/https://mariadb.com/kb/en/declare-condition/[ %LCASESyntax ------ LCASE(str) Description ----------- LCASE() is a synonym for LOWER(). URL: https://mariadb.com/kb/en/lcase/https://mariadb.com/kb/en/lcase/\^%LEFTSyntax ------ LEFT(str,len) Description ----------- Returns the leftmost len characters from the string str, or NULL if any argument is NULL. Examples -------- SELECT LEFT('MariaDB', 5); +--------------------+ | LEFT('MariaDB', 5) | +--------------------+ | Maria | +--------------------+ URL: https://mariadb.com/kb/en/left/https://mariadb.com/kb/en/left/^"%LENGTHBIntroduced in MariaDB 10.3.1 as part of the Oracle compatibility enhancements. Syntax ------ LENGTHB(str) Description ----------- LENGTHB() is a synonym for LENGTH(). URL: https://mariadb.com/kb/en/lengthb/https://mariadb.com/kb/en/lengthb/g4%MIDSyntax ------ MID(str,pos,len) Description ----------- MID(str,pos,len) is a synonym for SUBSTRING(str,pos,len). Examples -------- SELECT MID('abcd',4,1); +-----------------+ | MID('abcd',4,1) | +-----------------+ | d | +-----------------+ SELECT MID('abcd',2,2); +-----------------+ | MID('abcd',2,2) | +-----------------+ | bc | +-----------------+ A negative starting position: SELECT MID('abcd',-2,4); +------------------+ | MID('abcd',-2,4) | +------------------+ | cd | +------------------+ URL: https://mariadb.com/kb/en/mid/https://mariadb.com/kb/en/mid/h#%NOT LIKESyntax ------ expr NOT LIKE pat [ESCAPE 'escape_char'] Description ----------- This is the same as NOT (expr LIKE pat [ESCAPE 'escape_char']). URL: https://mariadb.com/kb/en/not-like/https://mariadb.com/kb/en/not-like/ckr  t '1*DECLARE HANDLERSyntax ------ DECLARE handler_type HANDLER FOR condition_value [, condition_value] ... statement handler_type: CONTINUE | EXIT | UNDO condition_value: SQLSTATE [VALUE] sqlstate_value | condition_name | SQLWARNING | NOT FOUND | SQLEXCEPTION | mariadb_error_code Description ----------- The DECLARE ... HANDLER statement specifies handlers that each may deal with one or more conditions. If one of these conditions occurs, the specified statement is executed. statement can be a simple statement (for example, SET var_name = value), or it can be a compound statement written using BEGIN and END. Handlers must be declared after local variables, a CONDITION and a CURSOR. For a CONTINUE handler, execution of the current program continues after execution of the handler statement. For an EXIT handler, execution terminates for the BEGIN ... END compound statement in which the handler is declared. (This is true even if the condition occurs in an inner block.) The UNDO handler type statement is not supported. If a condition occurs for which no handler has been declared, the default action is EXIT. A condition_value for DECLARE ... HANDLER can be any of the following values: An SQLSTATE value (a 5-character string literal) or a MariaDB error code (a number). You should not use SQLSTATE value '00000' or MariaDB error code 0, because those indicate sucess rather than an error condition. For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes. A condition name previously specified with DECLARE ... CONDITION. It must be in the same stored program. See DECLARE CONDITION. SQLWARNING is shorthand for the class of SQLSTATE values that begin with '01'. NOT FOUND is shorthand for the class of SQLSTATE values that begin with '02'. This is relevant only the context of cursors and is used to control what happens when a cursor reaches the end of a data set. If no more rows are available, a No Data condition occurs with SQLSTATE value 02000. To detect this condition, you can set up a handler for it (or for a NOT FOUND condition). An example is shown in Cursor Overview. This condition also occurs for SELECT ... INTO var_list statements that retrieve no rows. SQLEXCEPTION is shorthand for the class of SQLSTATE values that do not begin with '00', '01', or '02'. When an error raises, in some cases it could be handled by multiple HANDLERs. For example, there may be an handler for 1050 error, a separate handler for the 42S01 SQLSTATE, and another separate handler for the SQLEXCEPTION class: in theory all occurrences of HANDLER may catch the 1050 error, but MariaDB chooses the HANDLER with the highest precedence. Here are the precedence rules: Handlers which refer to an error code have the highest precedence. Handlers which refer to a SQLSTATE come next. Handlers which refer to an error class have the lowest precedence. In some cases, a statement could produce multiple errors. If this happens, in some cases multiple handlers could have the highest precedence. In such cases, the choice of the handler is indeterminate. Note that if an error occurs within a CONTINUE HANDLER block, it can be handled by another HANDLER. However, a HANDLER which is already in the stack (that is, it has been called to handle an error and its execution didn't finish yet) cannot handle new errors—this prevents endless loops. For example, suppose that a stored procedure contains a CONTINUE HANDLER for SQLWARNING and another CONTINUE HANDLER for NOT FOUND. At some point, a NOT FOUND error occurs, and the execution enters the NOT FOUND HANDLER. But within that handler, a warning occurs, and the execution enters the SQLWARNING HANDLER. If another NOT FOUND error occurs, it cannot be handled again by the NOT FOUND HANDLER, because its execution is not finished. When a DECLARE HANDLER block can handle more than one error condition, it may be useful to know which errors occurred. To do so, you can use the GET DIAGNOSTICS statement. An error that is handled by a DECLARE HANDLER construct can be issued again using the RESIGNAL statement. Below is an example using DECLARE HANDLER: CREATE TABLE test.t (s1 INT, PRIMARY KEY (s1)); DELIMITER // CREATE PROCEDURE handlerdemo ( ) BEGIN DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x2 = 1; SET @x = 1; INSERT INTO test.t VALUES (1); SET @x = 2; INSERT INTO test.t VALUES (1); SET @x = 3; END; // DELIMITER ; CALL handlerdemo( ); SELECT @x; +------+ | @x | +------+ | 3 | +------+ URL: https://mariadb.com/kb/en/declare-handler/https://mariadb.com/kb/en/declare-handler/2M +DECLARE VariableSyntax ------ DECLARE var_name [, var_name] ... [[ROW] TYPE OF]] type [DEFAULT value] Description ----------- This statement is used to declare local variables within stored programs. To provide a default value for the variable, include a DEFAULT clause. The value can be specified as an expression (even subqueries are permitted); it need not be a constant. If the DEFAULT clause is missing, the initial value is NULL. Local variables are treated like stored routine parameters with respect to data type and overflow checking. See CREATE PROCEDURE. Local variables must be declared before CONDITIONs, CURSORs and HANDLERs. Local variable names are not case sensitive. The scope of a local variable is within the BEGIN ... END block where it is declared. The variable can be referred to in blocks nested within the declaring block, except those blocks that declare a variable with the same name. TYPE OF / ROW TYPE OF TYPE OF and ROW TYPE OF anchored data types for stored routines were introduced in MariaDB 10.3. Anchored data types allow a data type to be defined based on another object, such as a table row, rather than specifically set in the declaration. If the anchor object changes, so will the anchored data type. This can lead to routines being easier to maintain, so that if the data type in the table is changed, it will automatically be changed in the routine as well. Variables declared with ROW TYPE OF will have the same features as implicit ROW variables. It is not possible to use ROW TYPE OF variables in a LIMIT clause. The real data type of TYPE OF and ROW TYPE OF table_name will become known at the very beginning of the stored routine call. ALTER TABLE or DROP TABLE statements performed inside the current routine on the tables that appear in anchors won't affect the data type of the anchored variables, even if the variable is declared after an ALTER TABLE or DROP TABLE statement. The real data type of a ROW TYPE OF cursor_name variable will become known when execution enters into the block where the variable is declared. Data type instantiation will happen only once. In a cursor ROW TYPE OF variable that is declared inside a loop, its data type will become known on the very first iteration and won't change on further loop iterations. The tables referenced in TYPE OF and ROW TYPE OF declarations will be checked for existence at the beginning of the stored routine call. CREATE PROCEDURE or CREATE FUNCTION will not check the referenced tables for existence. Examples -------- TYPE OF and ROW TYPE OF from MariaDB 10.3: DECLARE tmp TYPE OF t1.a; -- Get the data type from the column {{a}} in the table {{t1}} DECLARE rec1 ROW TYPE OF t1; -- Get the row data type from the table {{t1}} DECLARE rec2 ROW TYPE OF cur1; -- Get the row data type from the cursor {{cur1}} URL: https://mariadb.com/kb/en/declare-variable/https://mariadb.com/kb/en/declare-variable/E 9\Uzw4X FORFOR loops were introduced in MariaDB 10.3. Syntax ------ Integer range FOR loop: [begin_label:] FOR var_name IN [ REVERSE ] lower_bound .. upper_bound DO statement_list END FOR [ end_label ] Explicit cursor FOR loop [begin_label:] FOR record_name IN cursor_name [ ( cursor_actual_parameter_list)] DO statement_list END FOR [ end_label ] Explicit cursor FOR loop (Oracle mode) [begin_label:] FOR record_name IN cursor_name [ ( cursor_actual_parameter_list)] LOOP statement_list END LOOP [ end_label ] Implicit cursor FOR loop [begin_label:] FOR record_name IN ( select_statement ) DO statement_list END FOR [ end_label ] Description ----------- FOR loops allow code to be executed a fixed number of times. In an integer range FOR loop, MariaDB will compare the lower bound and upper bound values, and assign the lower bound value to a counter. If REVERSE is not specified, and the upper bound value is greater than or equal to the counter, the counter will be incremented and the statement will continue, after which the loop is entered again. If the upper bound value is greater than the counter, the loop will be exited. If REVERSE is specified, the counter is decremented, and the upper bound value needs to be less than or equal for the loop to continue. Examples -------- Intger range FOR loop: CREATE TABLE t1 (a INT); DELIMITER // FOR i IN 1..3 DO INSERT INTO t1 VALUES (i); END FOR; // DELIMITER ; SELECT * FROM t1; +------+ | a | +------+ | 1 | | 2 | | 3 | +------+ REVERSE integer range FOR loop: CREATE OR REPLACE TABLE t1 (a INT); DELIMITER // FOR i IN REVERSE 12..4 DO INSERT INTO t1 VALUES (i); END FOR; // Query OK, 9 rows affected (0.422 sec) DELIMITER ; SELECT * FROM t1; +------+ | a | +------+ | 12 | | 11 | | 10 | | 9 | | 8 | | 7 | | 6 | | 5 | | 4 | +------+ Explicit cursor in Oracle mode: SET sql_mode=ORACLE; CREATE OR REPLACE TABLE t1 (a INT, b VARCHAR(32)); INSERT INTO t1 VALUES (10,'b0'); INSERT INTO t1 VALUES (11,'b1'); INSERT INTO t1 VALUES (12,'b2'); DELIMITER // CREATE OR REPLACE PROCEDURE p1(pa INT) AS CURSOR cur(va INT) IS SELECT a, b FROM t1 WHERE a=va; BEGIN FOR rec IN cur(pa) LOOP SELECT rec.a, rec.b; END LOOP; END; // DELIMITER ; CALL p1(10); +-------+-------+ | rec.a | rec.b | +-------+-------+ | 10 | b0 | +-------+-------+ CALL p1(11); +-------+-------+ | rec.a | rec.b | +-------+-------+ | 11 | b1 | +-------+-------+ CALL p1(12); +-------+-------+ | rec.a | rec.b | +-------+-------+ | 12 | b2 | +-------+-------+ CALL p1(13); Query OK, 0 rows affected (0.000 sec) URL: https://mariadb.com/kb/en/for/https://mariadb.com/kb/en/for/8!LabelsSyntax ------ label: [label] Labels are MariaDB identifiers which can be used to identify a BEGIN ... END construct or a loop. They have a maximum length of 16 characters and can be quoted with backticks (i.e.., `). Labels have a start part and an end part. The start part must precede the portion of code it refers to, must be followed by a colon (:) and can be on the same or different line. The end part is optional and adds nothing, but can make the code more readable. If used, the end part must precede the construct's delimiter (;). Constructs identified by a label can be nested. Each construct can be identified by only one label. Labels need not be unique in the stored program they belong to. However, a label for an inner loop cannot be identical to a label for an outer loop. In this case, the following error would be produced: ERROR 1309 (42000): Redefining label LEAVE and ITERATE statements can be used to exit or repeat a portion of code identified by a label. They must be in the same Stored Routine, Trigger or Event which contains the target label. Below is an example using a simple label that is used to exit a LOOP: CREATE PROCEDURE `test_sp`() BEGIN `my_label`: LOOP SELECT 'looping'; LEAVE `my_label`; END LOOP; SELECT 'out of loop'; END; The following label is used to exit a procedure, and has an end part: CREATE PROCEDURE `test_sp`() `my_label`: BEGIN IF @var = 1 THEN LEAVE `my_label`; END IF; DO something(); END `my_label`; URL: https://mariadb.com/kb/en/labels/https://mariadb.com/kb/en/labels/9 LEAVESyntax ------ LEAVE label This statement is used to exit the flow control construct that has the given label. The label must be in the same stored program, not in a caller procedure. LEAVE can be used within BEGIN ... END or loop constructs (LOOP, REPEAT, WHILE). In Stored Procedures, Triggers and Events, LEAVE can refer to the outmost BEGIN ... END construct; in that case, the program exits the procedure. In Stored Functions, RETURN can be used instead. Note that LEAVE cannot be used to exit a DECLARE HANDLER block. If you try to LEAVE a non-existing label, or if you try to LEAVE a HANDLER block, the following error will be produced: ERROR 1308 (42000): LEAVE with no matching label: The following example uses LEAVE to exit the procedure if a condition is true: CREATE PROCEDURE proc(IN p TINYINT) CONTAINS SQL `whole_proc`: BEGIN SELECT 1; IF p URL: https://mariadb.com/kb/en/leave/https://mariadb.com/kb/en/leave/i %%NOT REGEXPSyntax ------ expr NOT REGEXP pat, expr NOT RLIKE pat Description ----------- This is the same as NOT (expr REGEXP pat). URL: https://mariadb.com/kb/en/not-regexp/https://mariadb.com/kb/en/not-regexp/j ('%OCTET_LENGTHSyntax ------ OCTET_LENGTH(str) Description ----------- OCTET_LENGTH() is normally a synonym for LENGTH(). When running Oracle mode from MariaDB 10.3, they are not synonyms, but OCTET_LENGTH() behaves as LENGTH() would when not in Oracle mode. URL: https://mariadb.com/kb/en/octet_length/https://mariadb.com/kb/en/octet_length/k5%ORDSyntax ------ ORD(str) Description ----------- If the leftmost character of the string str is a multi-byte character, returns the code for that character, calculated from the numeric values of its constituent bytes using this formula: (1st byte code) + (2nd byte code x 256) + (3rd byte code x 256 x 256) ... If the leftmost character is not a multi-byte character, ORD() returns the same value as the ASCII() function. Examples -------- SELECT ORD('2'); +----------+ | ORD('2') | +----------+ | 50 | +----------+ URL: https://mariadb.com/kb/en/ord/https://mariadb.com/kb/en/ord/l#%POSITIONSyntax ------ POSITION(substr IN str) Description ----------- POSITION(substr IN str) is a synonym for LOCATE(substr,str). It's part of ODBC 3.0. URL: https://mariadb.com/kb/en/position/https://mariadb.com/kb/en/position/m %QUOTESyntax ------ QUOTE(str) Description ----------- Quotes a string to produce a result that can be used as a properly escaped data value in an SQL statement. The string is returned enclosed by single quotes and with each instance of single quote ("'"), backslash ("\"), ASCII NUL, and Control-Z preceded by a backslash. If the argument is NULL, the return value is the word "NULL" without enclosing single quotes. Examples -------- SELECT QUOTE("Don't!"); +-----------------+ | QUOTE("Don't!") | +-----------------+ | 'Don\'t!' | +-----------------+ SELECT QUOTE(NULL); +-------------+ | QUOTE(NULL) | +-------------+ | NULL | +-------------+ URL: https://mariadb.com/kb/en/quote/https://mariadb.com/kb/en/quote/pe di K rQJ< U&REPEAT LOOPSyntax ------ [begin_label:] REPEAT statement_list UNTIL search_condition END REPEAT [end_label] The statement list within a REPEAT statement is repeated until the search_condition is true. Thus, a REPEAT always enters the loop at least once. statement_list consists of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter. A REPEAT statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same. See Delimiters in the mysql client for more on client delimiter usage. DELIMITER // CREATE PROCEDURE dorepeat(p1 INT) BEGIN SET @x = 0; REPEAT SET @x = @x + 1; UNTIL @x > p1 END REPEAT; END // CALL dorepeat(1000)// SELECT @x// +------+ | @x | +------+ | 1001 | +------+ URL: https://mariadb.com/kb/en/repeat-loop/https://mariadb.com/kb/en/repeat-loop/=| #RESIGNALSyntax ------ RESIGNAL [error_condition] [SET error_property [, error_property] ...] error_condition: SQLSTATE [VALUE] 'sqlstate_value' | condition_name error_property: error_property_name = error_property_name: CLASS_ORIGIN | SUBCLASS_ORIGIN | MESSAGE_TEXT | MYSQL_ERRNO | CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | CATALOG_NAME | SCHEMA_NAME | TABLE_NAME | COLUMN_NAME | CURSOR_NAME Description ----------- The syntax of RESIGNAL and its semantics are very similar to SIGNAL. This statement can only be used within an error HANDLER. It produces an error, like SIGNAL. RESIGNAL clauses are the same as SIGNAL, except that they all are optional, even SQLSTATE. All the properties which are not specified in RESIGNAL, will be identical to the properties of the error that was received by the error HANDLER. For a description of the clauses, see diagnostics area. Note that RESIGNAL does not empty the diagnostics area: it just appends another error condition. RESIGNAL, without any clauses, produces an error which is identical to the error that was received by HANDLER. If used out of a HANDLER construct, RESIGNAL produces the following error: ERROR 1645 (0K000): RESIGNAL when handler not active In MariaDB 5.5, if a HANDLER contained a CALL to another procedure, that procedure could use RESIGNAL. Since MariaDB 10.0, trying to do this raises the above error. For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes. The following procedure tries to query two tables which don't exist, producing a 1146 error in both cases. Those errors will trigger the HANDLER. The first time the error will be ignored and the client will not receive it, but the second time, the error is re-signaled, so the client will receive it. CREATE PROCEDURE test_error( ) BEGIN DECLARE CONTINUE HANDLER FOR 1146 BEGIN IF @hide_errors IS FALSE THEN RESIGNAL; END IF; END; SET @hide_errors = TRUE; SELECT 'Next error will be ignored' AS msg; SELECT `c` FROM `temptab_one`; SELECT 'Next error won''t be ignored' AS msg; SET @hide_errors = FALSE; SELECT `c` FROM `temptab_two`; END; CALL test_error( ); +----------------------------+ | msg | +----------------------------+ | Next error will be ignored | +----------------------------+ +-----------------------------+ | msg | +-----------------------------+ | Next error won't be ignored | +-----------------------------+ ERROR 1146 (42S02): Table 'test.temptab_two' doesn't exist The following procedure re-signals an error, modifying only the error message to clarify the cause of the problem. CREATE PROCEDURE test_error() BEGIN DECLARE CONTINUE HANDLER FOR 1146 BEGIN RESIGNAL SET MESSAGE_TEXT = '`temptab` does not exist'; END; SELECT `c` FROM `temptab`; END; CALL test_error( ); ERROR 1146 (42S02): `temptab` does not exist As explained above, this works on MariaDB 5.5, but produces a 1645 error since 10.0. CREATE PROCEDURE handle_error() BEGIN RESIGNAL; END; CREATE PROCEDURE p() BEGIN DECLARE EXIT HANDLER FOR SQLEXCEPTION CALL p(); SIGNAL SQLSTATE '45000'; END; URL: https://mariadb.com/kb/en/resignal/https://mariadb.com/kb/en/resignal/? %SELECT INTOSyntax ------ SELECT col_name [, col_name] ... INTO var_name [, var_name] ... table_expr Description ----------- SELECT ... INTO enables selected columns to be stored directly into variables. No resultset is produced. The query should return a single row. If the query returns no rows, a warning with error code 1329 occurs (No data), and the variable values remain unchanged. If the query returns multiple rows, error 1172 occurs (Result consisted of more than one row). If it is possible that the statement may retrieve multiple rows, you can use LIMIT 1 to limit the result set to a single row. The INTO clause can also be specified at the end of the statement. In the context of such statements that occur as part of events executed by the Event Scheduler, diagnostics messages (not only errors, but also warnings) are written to the error log, and, on Windows, to the application event log. This statement can be used with both local variables and user-defined variables. For the complete syntax, see SELECT. Another way to set a variable's value is the SET statement. SELECT ... INTO results are not stored in the query cache even if SQL_CACHE is specified. Examples -------- SELECT id, data INTO @x,@y FROM test.t1 LIMIT 1; URL: https://mariadb.com/kb/en/selectinto/https://mariadb.com/kb/en/selectinto/q*%REPEAT FunctionSyntax ------ REPEAT(str,count) Description ----------- Returns a string consisting of the string str repeated count times. If count is less than 1, returns an empty string. Returns NULL if str or count are NULL. Examples -------- SELECT QUOTE(REPEAT('MariaDB ',4)); +------------------------------------+ | QUOTE(REPEAT('MariaDB ',4)) | +------------------------------------+ | 'MariaDB MariaDB MariaDB MariaDB ' | +------------------------------------+ URL: https://mariadb.com/kb/en/repeat-function/https://mariadb.com/kb/en/repeat-function/r4+%REPLACE FunctionSyntax ------ REPLACE(str,from_str,to_str) Description ----------- Returns the string str with all occurrences of the string from_str replaced by the string to_str. REPLACE() performs a case-sensitive match when searching for from_str. Examples -------- SELECT REPLACE('www.mariadb.org', 'w', 'Ww'); +---------------------------------------+ | REPLACE('www.mariadb.org', 'w', 'Ww') | +---------------------------------------+ | WwWwWw.mariadb.org | +---------------------------------------+ URL: https://mariadb.com/kb/en/replace-function/https://mariadb.com/kb/en/replace-function/sP"%REVERSESyntax ------ REVERSE(str) Description ----------- Returns the string str with the order of the characters reversed. Examples -------- SELECT REVERSE('desserts'); +---------------------+ | REVERSE('desserts') | +---------------------+ | stressed | +---------------------+ URL: https://mariadb.com/kb/en/reverse/https://mariadb.com/kb/en/reverse/tc %RIGHTSyntax ------ RIGHT(str,len) Description ----------- Returns the rightmost len characters from the string str, or NULL if any argument is NULL. Examples -------- SELECT RIGHT('MariaDB', 2); +---------------------+ | RIGHT('MariaDB', 2) | +---------------------+ | DB | +---------------------+ URL: https://mariadb.com/kb/en/right/https://mariadb.com/kb/en/right/y}VUQ z@!SIGNALSyntax ------ SIGNAL error_condition [SET error_property [, error_property] ...] error_condition: SQLSTATE [VALUE] 'sqlstate_value' | condition_name error_property: error_property_name = error_property_name: CLASS_ORIGIN | SUBCLASS_ORIGIN | MESSAGE_TEXT | MYSQL_ERRNO | CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | CATALOG_NAME | SCHEMA_NAME | TABLE_NAME | COLUMN_NAME | CURSOR_NAME SIGNAL empties the diagnostics area and produces a custom error. This statement can be used anywhere, but is generally useful when used inside a stored program. When the error is produced, it can be caught by a HANDLER. If not, the current stored program, or the current statement, will terminate with the specified error. Sometimes an error HANDLER just needs to SIGNAL the same error it received, optionally with some changes. Usually the RESIGNAL statement is the most convenient way to do this. error_condition can be an SQLSTATE value or a named error condition defined via DECLARE CONDITION. SQLSTATE must be a constant string consisting of five characters. These codes are standard to ODBC and ANSI SQL. For customized errors, the recommended SQLSTATE is '45000'. For a list of SQLSTATE values used by MariaDB, see the MariaDB Error Codes page. The SQLSTATE can be read via the API method mysql_sqlstate( ). To specify error properties user-defined variables and local variables can be used, as well as character set conversions (but you can't set a collation). The error properties, their type and their default values are explained in the diagnostics area page. Errors If the SQLSTATE is not valid, the following error like this will be produced: ERROR 1407 (42000): Bad SQLSTATE: '123456' If a property is specified more than once, an error like this will be produced: ERROR 1641 (42000): Duplicate condition information item 'MESSAGE_TEXT' If you specify a condition name which is not declared, an error like this will be produced: ERROR 1319 (42000): Undefined CONDITION: cond_name If MYSQL_ERRNO is out of range, you will get an error like this: ERROR 1231 (42000): Variable 'MYSQL_ERRNO' can't be set to the value of '0' Examples -------- Here's what happens if SIGNAL is used in the client to generate errors: SIGNAL SQLSTATE '01000'; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +---------+------+------------------------------------------+ | Level | Code | Message | +---------+------+------------------------------------------+ | Warning | 1642 | Unhandled user-defined warning condition | +---------+------+------------------------------------------+ 1 row in set (0.06 sec) SIGNAL SQLSTATE '02000'; ERROR 1643 (02000): Unhandled user-defined not found condition How to specify MYSQL_ERRNO and MESSAGE_TEXT properties: SIGNAL SQLSTATE '45000' SET MYSQL_ERRNO=30001, MESSAGE_TEXT='H ello, world!'; ERROR 30001 (45000): Hello, world! The following code shows how to use user variables, local variables and character set conversion with SIGNAL: CREATE PROCEDURE test_error(x INT) BEGIN DECLARE errno SMALLINT UNSIGNED DEFAULT 31001; SET @errmsg = 'Hello, world!'; IF x = 1 THEN SIGNAL SQLSTATE '45000' SET MYSQL_ERRNO = errno, MESSAGE_TEXT = @errmsg; ELSE SIGNAL SQLSTATE '45000' SET MYSQL_ERRNO = errno, MESSAGE_TEXT = _utf8'Hello, world!'; END IF; END; How to use named error conditions: CREATE PROCEDURE test_error(n INT) BEGIN DECLARE `too_big` CONDITION FOR SQLSTATE '45000'; IF n > 10 THEN SIGNAL `too_big`; END IF; END; In this example, we'll define a HANDLER for an error code. When the error occurs, we SIGNAL a more informative error which makes sense for our procedure: CREATE PROCEDURE test_error() BEGIN DECLARE EXIT HANDLER FOR 1146 BEGIN SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Temporary tables not found; did you call init() procedure?'; END; -- this will produce a 1146 error SELECT `c` FROM `temptab`; END; URL: https://mariadb.com/kb/en/signal/https://mariadb.com/kb/en/signal/E e%LINESTRINGSyntax ------ LineString(pt1,pt2,...) Description ----------- Constructs a WKB LineString value from a number of WKB Point arguments. If any argument is not a WKB Point, the return value is NULL. If the number of Point arguments is less than two, the return value is NULL. Examples -------- SET @ls = 'LineString(1 1,2 2,3 3)'; SELECT AsText(EndPoint(GeomFromText(@ls))); +-------------------------------------+ | AsText(EndPoint(GeomFromText(@ls))) | +-------------------------------------+ | POINT(3 3) | +-------------------------------------+ CREATE TABLE gis_line (g LINESTRING); INSERT INTO gis_line VALUES (LineFromText('LINESTRING(0 0,0 10,10 0)')), (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')), (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10))))); URL: https://mariadb.com/kb/en/linestring/https://mariadb.com/kb/en/linestring/x &%SOUNDS LIKESyntax ------ expr1 SOUNDS LIKE expr2 Description ----------- This is the same as SOUNDEX(expr1) = SOUNDEX(expr2). Example SELECT givenname, surname FROM users WHERE givenname SOUNDS LIKE "robert"; +-----------+---------+ | givenname | surname | +-----------+---------+ | Roberto | Castro | +-----------+---------+ URL: https://mariadb.com/kb/en/sounds-like/https://mariadb.com/kb/en/sounds-like/y> %SPACESyntax ------ SPACE(N) Description ----------- Returns a string consisting of N space characters. If N is NULL, returns NULL. Examples -------- SELECT QUOTE(SPACE(6)); +-----------------+ | QUOTE(SPACE(6)) | +-----------------+ | ' ' | +-----------------+ URL: https://mariadb.com/kb/en/space/https://mariadb.com/kb/en/space/z!%STRCMPSyntax ------ STRCMP(expr1,expr2) Description ----------- STRCMP() returns 0 if the strings are the same, -1 if the first argument is smaller than the second according to the current sort order, and 1 otherwise. Examples -------- SELECT STRCMP('text', 'text2'); +-------------------------+ | STRCMP('text', 'text2') | +-------------------------+ | -1 | +-------------------------+ SELECT STRCMP('text2', 'text'); +-------------------------+ | STRCMP('text2', 'text') | +-------------------------+ | 1 | +-------------------------+ SELECT STRCMP('text', 'text'); +------------------------+ | STRCMP('text', 'text') | +------------------------+ | 0 | +------------------------+ URL: https://mariadb.com/kb/en/strcmp/https://mariadb.com/kb/en/strcmp/{x!%SUBSTRDescription ----------- SUBSTR() is a synonym for SUBSTRING(). URL: https://mariadb.com/kb/en/substr/https://mariadb.com/kb/en/substr/ %UCASESyntax ------ UCASE(str) Description ----------- UCASE() is a synonym for UPPER(). URL: https://mariadb.com/kb/en/ucase/https://mariadb.com/kb/en/ucase/ %UPPERSyntax ------ UPPER(str) Description ----------- Returns the string str with all characters changed to uppercase according to the current character set mapping. The default is latin1 (cp1252 West European). SELECT UPPER(surname), givenname FROM users ORDER BY surname; +----------------+------------+ | UPPER(surname) | givenname | +----------------+------------+ | ABEL | Jacinto | | CASTRO | Robert | | COSTA | Phestos | | MOSCHELLA | Hippolytos | +----------------+------------+ UPPER() is ineffective when applied to binary strings (BINARY, VARBINARY, BLOB). The description of LOWER() shows how to perform lettercase conversion of binary strings. URL: https://mariadb.com/kb/en/upper/https://mariadb.com/kb/en/upper/afq 0E Kl"POLYGONSyntax ------ Polygon(ls1,ls2,...) Description ----------- Constructs a WKB Polygon value from a number of WKB LineString arguments. If any argument does not represent the WKB of a LinearRing (that is, not a closed and simple LineString) the return value is NULL. Note that according to the OpenGIS standard, a POLYGON should have exactly one ExteriorRing and all other rings should lie within that ExteriorRing and thus be the InteriorRings. Practically, however, some systems, including MariaDB's, permit polygons to have several 'ExteriorRings'. In the case of there being multiple, non-overlapping exterior rings ST_NUMINTERIORRINGS() will return 1. Examples -------- SET @g = ST_GEOMFROMTEXT('POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1))'); CREATE TABLE gis_polygon (g POLYGON); INSERT INTO gis_polygon VALUES (PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')), (PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))')), (PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0), Point(30, 0), Point(30, 30), Point(0, 0)))))); Non-overlapping 'polygon': SELECT ST_NumInteriorRings(ST_PolyFromText('POLYGON((0 0,10 0,10 10,0 10,0 0), (-1 -1,-5 -1,-5 -5,-1 -5,-1 -1))')) AS NumInteriorRings; +------------------+ | NumInteriorRings | +------------------+ | 1 | +------------------+ URL: https://mariadb.com/kb/en/polygon/https://mariadb.com/kb/en/polygon/L $ST_BUFFERSyntax ------ ST_BUFFER(g1,r) BUFFER(g1,r) Description ----------- Returns a geometry that represents all points whose distance from geometry g1 is less than or equal to distance, or radius, r. Uses for this function could include creating for example a new geometry representing a buffer zone around an island. BUFFER() is a synonym. Examples -------- Determining whether a point is within a buffer zone: SET @g1 = ST_GEOMFROMTEXT('POLYGON((10 10, 10 20, 20 20, 20 10, 10 10))'); SET @g2 = ST_GEOMFROMTEXT('POINT(8 8)'); SELECT ST_WITHIN(@g2,ST_BUFFER(@g1,5)); +---------------------------------+ | ST_WITHIN(@g2,ST_BUFFER(@g1,5)) | +---------------------------------+ | 1 | +---------------------------------+ SELECT ST_WITHIN(@g2,ST_BUFFER(@g1,1)); +---------------------------------+ | ST_WITHIN(@g2,ST_BUFFER(@g1,1)) | +---------------------------------+ | 0 | +---------------------------------+ URL: https://mariadb.com/kb/en/st_buffer/https://mariadb.com/kb/en/st_buffer/M '(ST_CONVEXHULLST_ConvexHull() was introduced in MariaDB 10.1.2 Syntax ------ ST_ConvexHull(g) ConvexHull(g) Description ----------- Given a geometry, returns a geometry that is the minimum convex geometry enclosing all geometries within the set. Returns NULL if the geometry value is NULL or an empty value. ST_ConvexHull() and ConvexHull() are synonyms. Examples -------- The ConvexHull of a single point is simply the single point: SET @g = ST_GEOMFROMTEXT('Point(0 0)'); SELECT ST_ASTEXT(ST_CONVEXHULL(@g)); +------------------------------+ | ST_ASTEXT(ST_CONVEXHULL(@g)) | +------------------------------+ | POINT(0 0) | +------------------------------+ SET @g = ST_GEOMFROMTEXT('MultiPoint(0 0, 1 2, 2 3)'); SELECT ST_ASTEXT(ST_CONVEXHULL(@g)); +------------------------------+ | ST_ASTEXT(ST_CONVEXHULL(@g)) | +------------------------------+ | POLYGON((0 0,1 2,2 3,0 0)) | +------------------------------+ SET @g = ST_GEOMFROMTEXT('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9 3, 8 4, 6 6, 6 9, 4 9, 1 5 )'); SELECT ST_ASTEXT(ST_CONVEXHULL(@g)); +----------------------------------------+ | ST_ASTEXT(ST_CONVEXHULL(@g)) | +----------------------------------------+ | POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1)) | +----------------------------------------+ URL: https://mariadb.com/kb/en/st_convexhull/https://mariadb.com/kb/en/st_convexhull/P+ST_SYMDIFFERENCESyntax ------ ST_SYMDIFFERENCE(g1,g2) Description ----------- Returns a geometry that represents the portions of geometry g1 and geometry g2 that don't intersect. Examples -------- SET @g1 = ST_GEOMFROMTEXT('LINESTRING(10 20, 10 40)'); SET @g2 = ST_GEOMFROMTEXT('LINESTRING(10 15, 10 25)'); SELECT ASTEXT(ST_SYMDIFFERENCE(@g1,@g2)); +----------------------------------------------+ | ASTEXT(ST_SYMDIFFERENCE(@g1,@g2)) | +----------------------------------------------+ | MULTILINESTRING((10 15,10 20),(10 25,10 40)) | +----------------------------------------------+ SET @g2 = ST_GeomFromText('LINESTRING(10 20, 10 41)'); SELECT ASTEXT(ST_SYMDIFFERENCE(@g1,@g2)); +-----------------------------------+ | ASTEXT(ST_SYMDIFFERENCE(@g1,@g2)) | +-----------------------------------+ | LINESTRING(10 40,10 41) | +-----------------------------------+ URL: https://mariadb.com/kb/en/st_symdifference/https://mariadb.com/kb/en/st_symdifference/Q\#ST_UNIONSyntax ------ ST_UNION(g1,g2) Description ----------- Returns a geometry that is the union of the geometry g1 and geometry g2. Examples -------- SET @g1 = GEOMFROMTEXT('POINT (0 2)'); SET @g2 = GEOMFROMTEXT('POINT (2 0)'); SELECT ASTEXT(ST_UNION(@g1,@g2)); +---------------------------+ | ASTEXT(ST_UNION(@g1,@g2)) | +---------------------------+ | MULTIPOINT(2 0,0 2) | +---------------------------+ SET @g1 = GEOMFROMTEXT('POLYGON((0 0,0 3,3 3,3 0,0 0))'); SET @g2 = GEOMFROMTEXT('POLYGON((2 2,4 2,4 4,2 4,2 2))'); SELECT ASTEXT(ST_UNION(@g1,@g2)); +------------------------------------------------+ | ASTEXT(ST_UNION(@g1,@g2)) | +------------------------------------------------+ | POLYGON((0 0,0 3,2 3,2 4,4 4,4 2,3 2,3 0,0 0)) | +------------------------------------------------+ URL: https://mariadb.com/kb/en/st_union/https://mariadb.com/kb/en/st_union/c.'ALTER LOGFILE GROUPSyntax ------ ALTER LOGFILE GROUP logfile_group ADD UNDOFILE 'file_name' [INITIAL_SIZE [=] size] [WAIT] ENGINE [=] engine_name The ALTER LOGFILE GROUP statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. See MDEV-19295 for more information. URL: https://mariadb.com/kb/en/alter-logfile-group/https://mariadb.com/kb/en/alter-logfile-group/ ''ALTER SERVERSyntax ------ ALTER SERVER server_name OPTIONS (option [, option] ...) Description ----------- Alters the server information for server_name, adjusting the specified options as per the CREATE SERVER command. The corresponding fields in the mysql.servers table are updated accordingly. This statement requires the SUPER privilege. Examples -------- ALTER SERVER s OPTIONS (USER 'sally'); URL: https://mariadb.com/kb/en/alter-server/https://mariadb.com/kb/en/alter-server/@ Hl&'ALTER TABLE]+'ALTER TABLESPACEThe ALTER TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information. URL: https://mariadb.com/kb/en/alter-tablespace/https://mariadb.com/kb/en/alter-tablespace/@S(*'CREATE FUNCTION@+'CREATE PROCEDURE@ ''CREATE TABLE0Y-&3Q/U( j  JY\R 'BACKUP STAGEBACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. The BACKUP STAGE command was introduced in MariaDB 10.4.1. Syntax ------ BACKUP STAGE [START | FLUSH | BLOCK_DDL | BLOCK_COMMIT | END ] In the following text, a transactional table means InnoDB or "InnoDB-like engine with redo log that can lock redo purges and can be copied without locks by an outside process". In the text we refer to mariabackup as the backup tool to use. However the description should work for any tools that support BACKUP STAGEs. Goals with BACKUP STAGE Commands To be able to do a majority of the backup with the minimum possible server locks. Especially for transactional tables (InnoDB, MyRocks etc) there is only need for a very short block of new commits while copying statistics and log tables. DDL are only needed to be blocked for a very short duration of the backup while mariabackup is copying the tables affected by DDL during the initial part of the backup. Most non transactional tables (those that are not in use) will be copied during BACKUP STAGE START. The exceptions are system statistic and log tables that are not blocked during the backup until BLOCK_COMMIT. Should work efficiently with backup tools that use disk snapshots. Should work as efficiently as possible for all table types that store data on the local disks. As little copying as possible under higher level stages/locks. For example, .frm (dictionary) and .trn (trigger) files should be copying while copying the table data. BACKUP STAGE Commands BACKUP STAGE START Things Done by STAGE START Blocks purge of redo files for storage engines that needs this (Aria) Start logging of DDL commands into 'datadir'/ddl.log. This may take a short time as the command has to wait until there all now active DDL commands. mariabackup Under START mariabackup can, under START: Copy all transactional tables, aria_log_control, aria_log.# and other engines redo logs. Call BACKUP STAGE FLUSH while copying the last set of files. To copy InnoDB tables, mariabackup has to start to watch the InnoDB backup redo log and copy all changes to the backup to be able to run the redos later on in the final backup. BACKUP STAGE FLUSH Things Done by STAGE FLUSH FLUSH all changes for inactive non-transactional tables, except for statistics and log tables. Close all tables that are not in use, to ensure they are marked as closed for the backup. BLOCK all new write locks for all non transactional tables (except statistics and log tables). The command will not wait for tables that are in use by read-only transactions. DDLs don't have to be blocked at this stage as they can't cause the table to be in an inconsistent state. This is true also for non-transactional tables. mariabackup under STAGE_FLUSH mariabackup can, under STAGE FLUSH: Copy all non-transactional tables that are not in use. This list of used tables can be found with SHOW OPEN TABLES Copy all new changes to the aria_log.# tables At this point data for all old tables should have been copied (except for some system tables). BACKUP STAGE BLOCK_DDL Things Done by BLOCK_DDL Wait for all statements using write locked non-transactional tables to end. Blocks CREATE TABLE, DROP TABLE, TRUNCATE TABLE, and RENAME TABLE. Blocks also start off a new ALTER TABLE and the final rename phase of ALTER TABLE. Running ALTER TABLES are not blocked. mariabackup under BLOCK_DDL mariabackup can, under BLOCK_DDL: Copy the non-transactional tables that were in use during STAGE FLUSH Copy new tables created before BLOCK DDL. The file names can be read from ddl.log. The log also allows the backup to execute renames of files for which RENAME TABLE was done instead of copying them. Add markers to backup stream of tables that were dropped during the earlier BACKUP STAGEs. Copy changes to system log tables (this is easy as these are append only) Copy changes to aria_log.# tables (this is easy as these are append only) BACKUP STAGE BLOCK_COMMIT Things Done by BLOCK_COMMIT Lock the binary log and commit/rollback to ensure that no changes are committed to any tables. If there are active commits or data to be copied to the binary log this will be allowed to finish. This doesn't lock temporary tables that are not used by replication. However these will be blocked when it's time to write to the binary log. Lock system log tables and statistics tables, flush them and mark them closed. When the BLOCK_COMMIT's stages return, this is the 'backup time'. Everything committed will be in the backup and everything not committed will roll back. Transactional engines will continue to do changes to the redo log during the BLOCK COMMIT stage, but this is not important as all of these will roll back later as the changes will not be committed. mariabackup Under BLOCK_COMMIT mariabackup can, under BLOCK_COMMIT: Copy the last changes to the redo files for InnoDB and Aria (aria_log.#), and the part of the binary log that was not copied before. MyRocks files can also be hard linked to the backup directory End of system log tables (slow_log and general_log) and all statistics tables (table_stats, column_stats and index_stats) should also be copied. BACKUP STAGE END Things Done by END End DDL logging Free resources mariabackup After END mariabackup can, after END: Copy MyRocks tables Using BACKUP STAGE With Disk Snapshots A tool that is using disk snapshots for copying MariaDB files should do BACKUP STAGE START BACKUP STAGE BLOCK_COMMIT disk snapshot BACKUP STAGE END The above ensures that all non-transactional tables are properly flushed to disk before the snapshot is done. Using BACKUP STAGEs is also more efficient than using FLUSH TABLES WITH READ LOCK as the above set of commands will not block or be blocked by write operations to transactional tables. Note that when the backup is completed, one should delete all files with the "#sql" prefix, as these are files used by concurrent running ALTER TABLE. Note that InnoDB will on server restart automatically delete any tables with the "#sql" prefix. Privileges BACKUP STAGE requires the RELOAD privilege. Other Things Only one connection can run BACKUP STAGE START. If a second connection tries, it will wait until the first one has executed BACKUP STAGE END. If the user skips a BACKUP STAGE, all intermediate backup stages will automatically be run. This will allow us to add new BACKUP STAGEs in the future with even more precise locks without causing problems for tools using an earlier version of BACKUP STAGEs While opening files for a table, mariabackup should use BACKUP LOCK to ensure that all files for a table are from the same generation, that is, created at the same time. One can use the max_statement_time or lock_wait_timeout variables to ensure that a BACKUP STAGE command doesn't block the server too long. DDL logging will only be available in MariaDB Enterprise server 10.2, 10.3 and 10.4. URL: https://mariadb.com/kb/en/backup-stage/https://mariadb.com/kb/en/backup-stage/_,'CREATE TABLESPACEThe CREATE TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information. URL: https://mariadb.com/kb/en/create-tablespace/https://mariadb.com/kb/en/create-tablespace/ <]r S e&BACKUP LOCKThe BACKUP LOCK command was introduced in MariaDB 10.4.2. BACKUP LOCK blocks a table from DDL statements. This is mainly intended to be used by tools like mariabackup that need to ensure there are no DDLs on a table while the table files are opened. For example, for an Aria table that stores data in 3 files with extensions .frm, .MAI and .MAD. Normal read/write operations can continue as normal. Syntax ------ To lock a table: BACKUP LOCK table_name To unlock a table: BACKUP UNLOCK Usage in a Backup Tool BACKUP LOCK [database.]table_name; - Open all files related to a table (for example, t.frm, t.MAI and t.MYD) BACKUP UNLOCK; - Copy data - Close files This ensures that all files are from the same generation, that is created at the same time by the MariaDB server. Privileges BACKUP LOCK requires the RELOAD privilege. Notes The idea is that the BACKUP LOCK should be held for as short a time as possible by the backup tool. The time to take an uncontested lock is very short! One can easily do 50,000 locks/unlocks per second on low end hardware. One should use different connections for BACKUP STAGE commands and BACKUP LOCK. Implementation Internally, BACKUP LOCK is implemented by taking an MDLSHARED_HIGH_PRIO MDL lock on the table object, which protects the table from any DDL operations. URL: https://mariadb.com/kb/en/backup-lock/https://mariadb.com/kb/en/backup-lock/U &CACHE INDEXSyntax ------ CACHE INDEX tbl_index_list [, tbl_index_list] ... IN key_cache_name tbl_index_list: tbl_name [[INDEX|KEY] (index_name[, index_name] ...)] Description ----------- The CACHE INDEX statement assigns table indexes to a specific key cache. It is used only for MyISAM tables. A default key cache exists and cannot be destroyed. To create more key caches, the key_buffer_size server system variable. The associations between tables indexes and key caches are lost on server restart. To recreate them automatically, it is necessary to configure caches in a configuration file and include some CACHE INDEX (and optionally LOAD INDEX) statements in the init file. Examples -------- The following statement assigns indexes from the tables t1, t2, and t3 to the key cache named hot_cache: CACHE INDEX t1, t2, t3 IN hot_cache; +---------+--------------------+----------+----------+ | Table | Op | Msg_type | Msg_text | +---------+--------------------+----------+----------+ | test.t1 | assign_to_keycache | status | OK | | test.t2 | assign_to_keycache | status | OK | | test.t3 | assign_to_keycache | status | OK | +---------+--------------------+----------+----------+ Implementation (for MyISAM) Normally CACHE INDEX should not take a long time to execute. Internally it's implemented the following way: Find the right key cache (under LOCK_global_system_variables) Open the table with a TL_READ_NO_INSERT lock. Flush the original key cache for the given file (under key cache lock) Flush the new key cache for the given file (safety) Move the file to the new key cache (under file share lock) The only possible long operations are getting the locks for the table and flushing the original key cache, if there were many key blocks for the file in it. We plan to also add CACHE INDEX for Aria tables if there is a need for this. URL: https://mariadb.com/kb/en/cache-index/https://mariadb.com/kb/en/cache-index/X2FLUSH TABLES FOR EXPORTFLUSH TABLES ... FOR EXPORT was introduced in MariaDB 10.0.8. Syntax ------ FLUSH TABLES table_name [, table_name] FOR EXPORT Description ----------- FLUSH TABLES ... FOR EXPORT flushes changes to the specified tables to disk so that binary copies can be made while the server is still running. This works for Archive, Aria, CSV, InnoDB, MyISAM, MERGE, and XtraDB tables. The table is read locked until one has issued UNLOCK TABLES. If a storage engine does not support FLUSH TABLES FOR EXPORT, a 1031 error (SQLSTATE 'HY000') is produced. If FLUSH TABLES ... FOR EXPORT is in effect in the session, the following statements will produce an error if attempted: FLUSH TABLES WITH READ LOCK FLUSH TABLES ... WITH READ LOCK FLUSH TABLES ... FOR EXPORT Any statement trying to update any table If any of the following statements is in effect in the session, attempting FLUSH TABLES ... FOR EXPORT will produce an error. FLUSH TABLES ... WITH READ LOCK FLUSH TABLES ... FOR EXPORT LOCK TABLES ... READ LOCK TABLES ... WRITE FLUSH FOR EXPORT is not written to the binary log. This statement requires the RELOAD and the LOCK TABLES privileges. If one of the specified tables cannot be locked, none of the tables will be locked. If a table does not exist, an error like the following will be produced: ERROR 1146 (42S02): Table 'test.xxx' doesn't exist If a table is a view, an error like the following will be produced: ERROR 1347 (HY000): 'test.v' is not BASE TABLE Example FLUSH TABLES test.t1 FOR EXPORT; # Copy files related to the table (see below) UNLOCK TABLES; For a full description, please see copying MariaDB tables. URL: https://mariadb.com/kb/en/flush-tables-for-export/https://mariadb.com/kb/en/flush-tables-for-export/@ 8&'CREATE VIEW ''DROP PACKAGEOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ DROP PACKAGE [IF EXISTS] [ db_name . ] package_name Description ----------- The DROP PACKAGE statement can be used when Oracle SQL_MODE is set. The DROP PACKAGE statement drops a stored package entirely: Drops the package specification (earlier created using the CREATE PACKAGE statement). Drops the package implementation, if the implementation was already created using the CREATE PACKAGE BODY statement. URL: https://mariadb.com/kb/en/drop-package/https://mariadb.com/kb/en/drop-package/u,'DROP PACKAGE BODYOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ DROP PACKAGE BODY [IF EXISTS] [ db_name . ] package_name Description ----------- The DROP PACKAGE BODY statement can be used when Oracle SQL_MODE is set. The DROP PACKAGE BODY statement drops the package body (i.e the implementation), previously created using the CREATE PACKAGE BODY statement. Note, DROP PACKAGE BODY drops only the package implementation, but does not drop the package specification. Use DROP PACKAGE to drop the package entirely (i.e. both implementation and specification). URL: https://mariadb.com/kb/en/drop-package-body/https://mariadb.com/kb/en/drop-package-body/[*'DROP TABLESPACEThe DROP TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information. URL: https://mariadb.com/kb/en/drop-tablespace/https://mariadb.com/kb/en/drop-tablespace/@ e1LA,'Generated (Virtual and Persistent/Stored) Columnst"(LASTVALLASTVAL is a synonym for PREVIOUS VALUE for sequence_name. URL: https://mariadb.com/kb/en/lastval/https://mariadb.com/kb/en/lastval/p"(NEXTVALNEXTVAL is a synonym for NEXT VALUE for sequence_name. URL: https://mariadb.com/kb/en/nextval/https://mariadb.com/kb/en/nextval/ZZUWy(o   \Syntax ------ FLUSH [NO_WRITE_TO_BINLOG | LOCAL] flush_option [, flush_option] ... or when flushing tables: FLUSH [NO_WRITE_TO_BINLOG | LOCAL] TABLES [table_list] [table_flush_option] where table_list is a list of tables separated by , (comma). Description ----------- The FLUSH statement clears or reloads various internal caches used by MariaDB. To execute FLUSH, you must have the RELOAD privilege. See GRANT. The RESET statement is similar to FLUSH. See RESET. You cannot issue a FLUSH statement from within a stored function or a trigger. Doing so within a stored procedure is permitted, as long as it is not called by a stored function or trigger. See Stored Routine Limitations, Stored Function Limitations and Trigger Limitations. If a listed table is a view, an error like the following will be produced: ERROR 1347 (HY000): 'test.v' is not BASE TABLE By default, FLUSH statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log. The different flush options are: Option | Description | CHANGED_PAGE_BITMAPS | Internal command used for backup purposes. See the Information Schema CHANGED_PAGE_BITMAPS Table. | CLIENT_STATISTICS | Reset client statistics (see SHOW CLIENT_STATISTICS). | DES_KEY_FILE | Reloads the DES key file (Specified with the --des-key-file startup option). | HOSTS | Flush the hostname cache (used for converting ip to host names and for unblocking blocked hosts. See max_connect_errors) | INDEX_STATISTICS | Reset index statistics (see SHOW INDEX_STATISTICS). | [ERROR | ENGINE | GENERAL | SLOW | BINARY | RELAY] LOGS | Close and reopen the specified log type, or all log types if none are specified. FLUSH RELAY LOGS [connection-name] can be used to flush the relay logs for a specific connection. Only one connection can be specified per FLUSH command. See Multi-source replication. FLUSH ENGINE LOGS will delete all unneeded Aria redo logs. Since MariaDB 10.1.30 and MariaDB 10.2.11, FLUSH BINARY LOGS DELETE_DOMAIN_ID=(list-of-domains) can be used to discard obsolete GTID domains from the server's binary log state. In order for this to be successful, no event group from the listed GTID domains can be present in existing binary log files. If some still exist, then they must be purged prior to executing this command. If the command completes successfully, then it also rotates the binary log. | MASTER | Deprecated option, use RESET MASTER instead. | PRIVILEGES | Reload all privileges from the privilege tables in the mysql database. If the server is started with --skip-grant-table option, this will activate the privilege tables again. | QUERY CACHE | Defragment the query cache to better utilize its memory. If you want to reset the query cache, you can do it with RESET QUERY CACHE. | QUERY_RESPONSE_TIME | See the QUERY_RESPONSE_TIME plugin. | SLAVE | Deprecated option, use RESET SLAVE instead. | SSL | Used to dynamically reinitialize the server's TLS context by reloading the files defined by several TLS system variables. See FLUSH SSL for more information. This command was first added in MariaDB 10.4.1. | STATUS | Resets all server status variables that can be reset to 0. Not all global status variables support this, so not all global values are reset. See FLUSH STATUS for more information. | TABLE | Close tables given as options or all open tables if no table list was used. From MariaDB 10.4.1, using without any table list will only close tables not in use, and tables not locked by the FLUSH TABLES connection. If there are no locked tables, FLUSH TABLES will be instant and will not cause any waits, as it no longer waits for tables in use. When a table list is provided, from MariaDB 10.4.1, the server will wait for the end of any transactions that are using the tables. Previously, FLUSH TABLES only waited for the statements to complete. | TABLES | Same as FLUSH TABLE. | TABLES ... FOR EXPORT | For InnoDB tables, flushes table changes to disk to permit binary table copies while the server is running. Introduced in MariaDB 10.0.8. See FLUSH TABLES ... FOR EXPORT for more. | TABLES WITH READ LOCK | Closes all open tables. New tables are only allowed to be opened with read locks until an UNLOCK TABLES is given. | TABLES WITH READ LOCK AND DISABLE CHECKPOINT | As TABLES WITH READ LOCK but also disable all checkpoint writes by transactional table engines. This is useful when doing a disk snapshot of all tables. | TABLE_STATISTICS | Reset table statistics (see SHOW TABLE_STATISTICS). | USER_RESOURCES | Resets all per hour user resources. This enables clients that have exhausted their resources to connect again. | USER_STATISTICS | Reset user statistics (see SHOW USER_STATISTICS). | You can also use the mysqladmin client to flush things. Use mysqladmin --help to examine what flush commands it supports. FLUSH STATUS Server status variables can be reset by executing the following: FLUSH STATUS; Global Status Variables that Support FLUSH STATUS Not all global status variables support being reset by FLUSH STATUS. Currently, the following status variables are reset by FLUSH STATUS: Aborted_clients Aborted_connects Aria_pagecache_blocks_not_flushed Aria_pagecache_blocks_unused Aria_pagecache_blocks_used Binlog_cache_disk_use Binlog_cache_use Binlog_stmt_cache_disk_use Binlog_stmt_cache_use Connection_errors_accept Connection_errors_internal Connection_errors_max_connections Connection_errors_peer_address Connection_errors_select Connection_errors_tcpwrap Created_tmp_files Delayed_errors Delayed_writes Feature_check_constraint Feature_delay_key_write Max_used_connections Opened_plugin_libraries Performance_schema_accounts_lost Performance_schema_cond_instances_lost Performance_schema_digest_lost Performance_schema_file_handles_lost Performance_schema_file_instances_lost Performance_schema_hosts_lost Performance_schema_locker_lost Performance_schema_mutex_instances_lost Performance_schema_rwlock_instances_lost Performance_schema_session_connect_attrs_lost Performance_schema_socket_instances_lost Performance_schema_stage_classes_lost Performance_schema_statement_classes_lost Performance_schema_table_handles_lost Performance_schema_table_instances_lost Performance_schema_thread_instances_lost Performance_schema_users_lost Qcache_hits Qcache_inserts Qcache_lowmem_prunes Qcache_not_cached Rpl_semi_sync_master_no_times Rpl_semi_sync_master_no_tx Rpl_semi_sync_master_timefunc_failures Rpl_semi_sync_master_wait_pos_backtraverse Rpl_semi_sync_master_yes_tx Rpl_transactions_multi_engine Server_audit_writes_failed Slave_retried_transactions Slow_launch_threads Ssl_accept_renegotiates Ssl_accepts Ssl_callback_cache_hits Ssl_client_connects Ssl_connect_renegotiates Ssl_ctx_verify_depth Ssl_ctx_verify_mode Ssl_finished_accepts Ssl_finished_connects Ssl_session_cache_hits Ssl_session_cache_misses Ssl_session_cache_overflows Ssl_session_cache_size Ssl_session_cache_timeouts Ssl_sessions_reused Ssl_used_session_cache_entries Subquery_cache_hit Subquery_cache_miss Table_locks_immediate Table_locks_waited Tc_log_max_pages_used Tc_log_page_waits Transactions_gtid_foreign_engine Transactions_multi_engine FLUSH SSL The FLUSH SSL command was first added in MariaDB 10.4. In MariaDB 10.4 and later, the FLUSH SSL command can be used to dynamically reinitialize the server's TLS context. This is most useful if you need to replace a certificate that is about to expire without restarting the server. This operation is performed by reloading the files defined by the following TLS system variables: ssl_cert ssl_key ssl_ca ssl_capath ssl_crl ssl_crlpath These TLS system variables are not dynamic, so their values can not be changed without restarting the server. If you want to dynamically reinitialize the server's TLS context, then you need to change the certificate and key files at the relevant paths defined by these TLS system variables, without actually changing the values of the variables. See MDEV-19341 for more information. Reducing Memory Usage 8A$Y 'HELP CommandSyntax ------ HELP search_string Description ----------- The HELP command can be used in any MariaDB client, such as the mysql command-line client, to get basic syntax help and a short description for most commands and functions. If you provide an argument to the HELP command, the mysql client uses it as a search string to access server-side help. The proper operation of this command requires that the help tables in the mysql database be initialized with help topic information. If there is no match for the search string, the search fails. Use help contents to see a list of the help categories: HELP contents You asked for help about help category: "Contents" For more information, type 'help ', where is one of the following categories: Account Management Administration Compound Statements Data Definition Data Manipulation Data Types Functions Functions and Modifiers for Use with GROUP BY Geographic Features Help Metadata Language Structure Plugins Procedures Sequences Table Maintenance Transactions User-Defined Functions Utility If a search string matches multiple items, MariaDB shows a list of matching topics: HELP drop Many help items for your request exist. To make a more specific request, please type 'help ', where is one of the following topics: ALTER TABLE DROP DATABASE DROP EVENT DROP FUNCTION DROP FUNCTION UDF DROP INDEX DROP PACKAGE DROP PACKAGE BODY DROP PROCEDURE DROP ROLE DROP SEQUENCE DROP SERVER DROP TABLE DROP TRIGGER DROP USER DROP VIEW Then you can enter a topic as the search string to see the help entry for that topic. The help is provided with the MariaDB server and makes use of four help tables found in the mysql database: help_relation, help_topic, help_category and help_keyword. These tables are populated by the mysql_install_db or fill_help_table.sql scripts which, until MariaDB 10.4.7, contain data generated from an old version of MySQL. URL: https://mariadb.com/kb/en/help-command/https://mariadb.com/kb/en/help-command/ZX BKILL [CONNECTION | QUERY]Syntax ------ KILL [HARD | SOFT] [CONNECTION | QUERY [ID] ] [thread_id | USER user_name | query_id] MariaDB 5.3.2 The options HARD | SOFT and USER username were introduced in MariaDB 5.3.2 MariaDB 10.0.5 KILL QUERY ID query_id, which permits killing a query by query id rather than thread id, was introduced in MariaDB 10.0.5. Description ----------- Each connection to mysqld runs in a separate thread. You can see which threads are running with the SHOW PROCESSLIST statement and kill a thread with the KILL thread_id statement. KILL allows the optional CONNECTION or QUERY modifier: KILL CONNECTION is the same as KILL with no modifier: It terminates the connection associated with the given thread or query id. KILL QUERY terminates the statement that the connection thread_id is currently executing, but leaves the connection itself intact. KILL QUERY ID (introduced in MariaDB 10.0.5) terminates the query by query_id, leaving the connection intact. If a connection is terminated that has an active transaction, the transaction will be rolled back. If only a query is killed, the current transaction will stay active. See also idle_transaction_timeout. If you have the PROCESS privilege, you can see all threads. If you have the SUPER privilege, you can kill all threads and statements. Otherwise, you can see and kill only your own threads and statements. Killing queries that repair or create indexes on MyISAM and Aria tables may result in corrupted tables. Use the SOFT option to avoid this! The HARD option (default) kills a command as soon as possible. If you use SOFT, then critical operations that may leave a table in an inconsistent state will not be interrupted. Such operations include REPAIR and INDEX creation for MyISAM and Aria tables (REPAIR TABLE, OPTIMIZE TABLE). KILL ... USER username will kill all connections/queries for a given user. USER can be specified one of the following ways: username (Kill without regard to hostname) username@hostname CURRENT_USER or CURRENT_USER() If you specify a thread id and that thread does not exist, you get the following error: ERROR 1094 (HY000): Unknown thread id: If you specify a query id that doesn't exist, you get the following error: ERROR 1957 (HY000): Unknown query id: However, if you specify a user name, no error is issued for non-connected (or even non-existing) users. To check if the connection/query has been killed, you can use the ROW_COUNT() function. A client whose connection is killed receives the following error: ERROR 1317 (70100): Query execution was interrupted To obtain a list of existing sessions, use the SHOW PROCESSLIST statement or query the Information Schema PROCESSLIST table. Note: You cannot use KILL with the Embedded MySQL Server library because the embedded server merely runs inside the threads of the host application. It does not create any connection threads of its own. Note: You can also use mysqladmin kill thread_id [,thread_id...] to kill connections. To get a list of running queries, use mysqladmin processlist. See mysqladmin. Percona Toolkit contains a program, pt-kill that can be used to automatically kill connections that match certain criteria. For example, it can be used to terminate idle connections, or connections that have been busy for more than 60 seconds. URL: https://mariadb.com/kb/en/data-manipulation-kill-connection-query/https://mariadb.com/kb/en/data-manipulation-kill-connection-query/ G%)JSON_ARRAYJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_ARRAY([value[, value2] ...]) Description ----------- Returns a JSON array containing the listed values. The list can be empty. Example SELECT Json_Array(56, 3.1416, 'My name is "Foo"', NULL); +--------------------------------------------------+ | Json_Array(56, 3.1416, 'My name is "Foo"', NULL) | +--------------------------------------------------+ | [56, 3.1416, "My name is \"Foo\"", null] | +--------------------------------------------------+ URL: https://mariadb.com/kb/en/json_array/https://mariadb.com/kb/en/json_array/ ')JSON_COMPACTThis function was added in MariaDB 10.2.4. Syntax ------ JSON_COMPACT(json_doc) Description ----------- Removes all unnecessary spaces so the json document is as short as possible. Example SET @j = '{ "A": 1, "B": [2, 3]}'; SELECT JSON_COMPACT(@j), @j; +-------------------+------------------------+ | JSON_COMPACT(@j) | @j | +-------------------+------------------------+ | {"A":1,"B":[2,3]} | { "A": 1, "B": [2, 3]} | +-------------------+------------------------+ URL: https://mariadb.com/kb/en/json_compact/https://mariadb.com/kb/en/json_compact/ ()JSON_DETAILEDThis function was added in MariaDB 10.2.4. Syntax ------ JSON_DETAILED(json_doc[, tab_size]) Description ----------- Represents JSON in the most understandable way emphasizing nested structures. Example SET @j = '{ "A":1,"B":[2,3]}'; SELECT @j; +--------------------+ | @j | +--------------------+ | { "A":1,"B":[2,3]} | +--------------------+ SELECT JSON_DETAILED(@j); +------------------------------------------------------------+ | JSON_DETAILED(@j) | +------------------------------------------------------------+ | { "A": 1, "B": [ 2, 3 ] } | +------------------------------------------------------------+ URL: https://mariadb.com/kb/en/json_detailed/https://mariadb.com/kb/en/json_detailed/l^& &\ RESETSyntax ------ RESET reset_option [, reset_option] ... Description ----------- The RESET statement is used to clear the state of various server operations. You must have the RELOAD privilege to execute RESET. RESET acts as a stronger version of the FLUSH statement. The different RESET options are: Option | Description | SLAVE ["connection_name"] [ALL] | Deletes all relay logs from the slave and reset the replication position in the master binary log. | MASTER | Deletes all old binary logs, makes the binary index file (--log-bin-index) empty and creates a new binary log file. This is useful when you want to reset the master to an initial state. If you want to just delete old, not used binary logs, you should use the PURGE BINARY LOGS command. | QUERY CACHE | Removes all queries from the query cache. See also FLUSH QUERY CACHE. | URL: https://mariadb.com/kb/en/reset/https://mariadb.com/kb/en/reset/]SETSyntax ------ SET variable_assignment [, variable_assignment] ... variable_assignment: user_var_name = expr | [GLOBAL | SESSION] system_var_name = expr | [@@global. | @@session. | @@]system_var_name = expr One can also set a user variable in any expression with this syntax: user_var_name:= expr Description ----------- The SET statement assigns values to different types of variables that affect the operation of the server or your client. Older versions of MySQL employed SET OPTION, but this syntax was deprecated in favor of SET without OPTION, and was removed in MariaDB 10.0. Changing a system variable by using the SET statement does not make the change permanently. To do so, the change must be made in a configuration file. For setting variables on a per-query basis (from MariaDB 10.1.2), see SET STATEMENT. See SHOW VARIABLES for documentation on viewing server system variables. See Server System Variables for a list of all the system variables. GLOBAL / SESSION When setting a system variable, the scope can be specified as either GLOBAL or SESSION. A global variable change affects all new sessions. It does not affect any currently open sessions, including the one that made the change. A session variable change affects the current session only. If the variable has a session value, not specifying either GLOBAL or SESSION will be the same as specifying SESSION. If the variable only has a global value, not specifying GLOBAL or SESSION will apply to the change to the global value. DEFAULT Setting a global variable to DEFAULT will restore it to the server default, and setting a session variable to DEFAULT will restore it to the current global value. Examples -------- innodb_sync_spin_loops is a global variable. skip_parallel_replication is a session variable. max_error_count is both global and session. SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE VARIABLE_NAME LIKE 'max_error_count' OR VARIABLE_NAME LIKE 'skip_parallel_replication' OR VARIABLE_NAME LIKE 'innodb_sync_spin_loops'; +---------------------------+---------------+--------------+ | VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE | +---------------------------+---------------+--------------+ | MAX_ERROR_COUNT | 64 | 64 | | SKIP_PARALLEL_REPLICATION | OFF | NULL | | INNODB_SYNC_SPIN_LOOPS | NULL | 30 | +---------------------------+---------------+--------------+ Setting the session values: SET max_error_count=128; Query OK, 0 rows affected (0.000 sec) SET skip_parallel_replication=ON; Query OK, 0 rows affected (0.000 sec) SET innodb_sync_spin_loops=60; ERROR 1229 (HY000): Variable 'innodb_sync_spin_loops' is a GLOBAL variable and should be set with SET GLOBAL SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE VARIABLE_NAME LIKE 'max_error_count' OR VARIABLE_NAME LIKE 'skip_parallel_replication' OR VARIABLE_NAME LIKE 'innodb_sync_spin_loops'; +---------------------------+---------------+--------------+ | VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE | +---------------------------+---------------+--------------+ | MAX_ERROR_COUNT | 128 | 64 | | SKIP_PARALLEL_REPLICATION | ON | NULL | | INNODB_SYNC_SPIN_LOOPS | NULL | 30 | +---------------------------+---------------+--------------+ Setting the global values: SET GLOBAL max_error_count=256; SET GLOBAL skip_parallel_replication=ON; ERROR 1228 (HY000): Variable 'skip_parallel_replication' is a SESSION variable and can't be used with SET GLOBAL SET GLOBAL innodb_sync_spin_loops=120; SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE VARIABLE_NAME LIKE 'max_error_count' OR VARIABLE_NAME LIKE 'skip_parallel_replication' OR VARIABLE_NAME LIKE 'innodb_sync_spin_loops'; +---------------------------+---------------+--------------+ | VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE | +---------------------------+---------------+--------------+ | MAX_ERROR_COUNT | 128 | 256 | | SKIP_PARALLEL_REPLICATION | ON | NULL | | INNODB_SYNC_SPIN_LOOPS | NULL | 120 | +---------------------------+---------------+--------------+ SHOW VARIABLES will by default return the session value unless the variable is global only. SHOW VARIABLES LIKE 'max_error_count'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_error_count | 128 | +-----------------+-------+ SHOW VARIABLES LIKE 'skip_parallel_replication'; +---------------------------+-------+ | Variable_name | Value | +---------------------------+-------+ | skip_parallel_replication | ON | +---------------------------+-------+ SHOW VARIABLES LIKE 'innodb_sync_spin_loops'; +------------------------+-------+ | Variable_name | Value | +------------------------+-------+ | innodb_sync_spin_loops | 120 | +------------------------+-------+ Using the inplace syntax: SELECT (@a:=1); +---------+ | (@a:=1) | +---------+ | 1 | +---------+ SELECT @a; +------+ | @a | +------+ | 1 | +------+ URL: https://mariadb.com/kb/en/set/https://mariadb.com/kb/en/set/ %)JSON_LOOSEThis function was added in MariaDB 10.2.4. Syntax ------ JSON_LOOSE(json_doc) Description ----------- Adds spaces to a JSON document to make it look more readable. Example SET @j = '{ "A":1,"B":[2,3]}'; SELECT JSON_LOOSE(@j), @j; +-----------------------+--------------------+ | JSON_LOOSE(@j) | @j | +-----------------------+--------------------+ | {"A": 1, "B": [2, 3]} | { "A":1,"B":[2,3]} | +-----------------------+--------------------+ URL: https://mariadb.com/kb/en/json_loose/https://mariadb.com/kb/en/json_loose/ x&)JSON_OBJECTJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_OBJECT([key, value[, key, value] ...]) Description ----------- Returns a JSON object containing the given key/value pairs. The key/value list can be empty. An error will occur if there are an odd number of arguments, or any key name is NULL. Example SELECT JSON_OBJECT("id", 1, "name", "Monty"); +---------------------------------------+ | JSON_OBJECT("id", 1, "name", "Monty") | +---------------------------------------+ | {"id": 1, "name": "Monty"} | +---------------------------------------+ URL: https://mariadb.com/kb/en/json_object/https://mariadb.com/kb/en/json_object/>?, >W^ ,%About SHOWSHOW has many forms that provide information about databases, tables, columns, or status information about the server. These include: SHOW AUTHORS SHOW CHARACTER SET [like_or_where] SHOW COLLATION [like_or_where] SHOW [FULL] COLUMNS FROM tbl_name [FROM db_name] [like_or_where] SHOW CONTRIBUTORS SHOW CREATE DATABASE db_name SHOW CREATE EVENT event_name SHOW CREATE PACKAGE package_name SHOW CREATE PACKAGE BODY package_name SHOW CREATE PROCEDURE proc_name SHOW CREATE TABLE tbl_name SHOW CREATE TRIGGER trigger_name SHOW CREATE VIEW view_name SHOW DATABASES [like_or_where] SHOW ENGINE engine_name {STATUS | MUTEX} SHOW [STORAGE] ENGINES SHOW ERRORS [LIMIT [offset,] row_count] SHOW [FULL] EVENTS SHOW FUNCTION CODE func_name SHOW FUNCTION STATUS [like_or_where] SHOW GRANTS FOR user SHOW INDEX FROM tbl_name [FROM db_name] SHOW INNODB STATUS SHOW OPEN TABLES [FROM db_name] [like_or_where] SHOW PLUGINS SHOW PROCEDURE CODE proc_name SHOW PROCEDURE STATUS [like_or_where] SHOW PRIVILEGES SHOW [FULL] PROCESSLIST SHOW PROFILE [types] [FOR QUERY n] [OFFSET n] [LIMIT n] SHOW PROFILES SHOW [GLOBAL | SESSION] STATUS [like_or_where] SHOW TABLE STATUS [FROM db_name] [like_or_where] SHOW TABLES [FROM db_name] [like_or_where] SHOW TRIGGERS [FROM db_name] [like_or_where] SHOW [GLOBAL | SESSION] VARIABLES [like_or_where] SHOW WARNINGS [LIMIT [offset,] row_count] like_or_where: LIKE 'pattern' | WHERE expr If the syntax for a given SHOW statement includes a LIKE 'pattern' part, 'pattern' is a string that can contain the SQL "%" and "_" wildcard characters. The pattern is useful for restricting statement output to matching values. Several SHOW statements also accept a WHERE clause that provides more flexibility in specifying which rows to display. See Extended Show. URL: https://mariadb.com/kb/en/about-show/https://mariadb.com/kb/en/about-show/_  'SHOW AUTHORSSyntax ------ SHOW AUTHORS Description ----------- The SHOW AUTHORS statement displays information about the people who work on MariaDB. For each author, it displays Name, Location, and Comment values. All columns are encoded as latin1. In MariaDB 5.5 this is in somewhat random order. In MariaDB 10.0.5 and later you have: First the active people in MariaDB are listed. Then the active people in MySQL. Last the people that has contributed to MariaDB/MySQL in the past. The order is somewhat related to importance of the contribution given to the MariaDB project, but this is not 100% accurate. There is still room for improvements and debate... Example SHOW AUTHORS; +--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+ | Name | Location | Comment | +--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+ | Michael (Monty) Widenius | Tusby, Finland | Lead developer and main author | | Sergei Golubchik | Kerpen, Germany | Architect, Full-text search, precision math, plugin framework, merges etc | | Igor Babaev | Bellevue, USA | Optimizer, keycache, core work | | Sergey Petrunia | St. Petersburg, Russia | Optimizer | | Oleksandr Byelkin | Lugansk, Ukraine | Query Cache (4.0), Subqueries (4.1), Views (5.0) | | Timour Katchaounov | Sofia , Bulgaria | Optimizer | | Kristian Nielsen | Copenhagen, Denmark | Replication, Async client prototocol, General buildbot stuff | | Alexander (Bar) Barkov | Izhevsk, Russia | Unicode and character sets | | Alexey Botchkov (Holyfoot) | Izhevsk, Russia | GIS extensions, embedded server, precision math | | Daniel Bartholomew | Raleigh, USA | MariaDB documentation | | Colin Charles | Selangor, Malesia | MariaDB documentation, talks at a LOT of conferences | | Sergey Vojtovich | Izhevsk, Russia | initial implementation of plugin architecture, maintained native storage engines (MyISAM, MEMORY, ARCHIVE, etc), rewrite of table cache | | Vladislav Vaintroub | Mannheim, Germany | MariaDB Java connector, new thread pool, Windows optimizations | | Elena Stepanova | Sankt Petersburg, Russia | QA, test cases | | Georg Richter | Heidelberg, Germany | New LGPL C connector, PHP connector | | Jan Lindström | Ylämylly, Finland | Working on InnoDB | | Lixun Peng | Hangzhou, China | Multi Source replication | | Percona | CA, USA | XtraDB, microslow patches, extensions to slow log ... See Also SHOW CONTRIBUTORS. This list all members and sponsors of the MariaDB Foundation and other sponsors. URL: https://mariadb.com/kb/en/show-authors/https://mariadb.com/kb/en/show-authors/`+SHOW BINARY LOGSSyntax ------ SHOW BINARY LOGS SHOW MASTER LOGS Description ----------- Lists the binary log files on the server. This statement is used as part of the procedure described in PURGE BINARY LOGS, that shows how to determine which logs can be purged. Examples -------- SHOW BINARY LOGS; +--------------------+-----------+ | Log_name | File_size | +--------------------+-----------+ | mariadb-bin.000001 | 19039 | | mariadb-bin.000002 | 717389 | | mariadb-bin.000003 | 300 | | mariadb-bin.000004 | 333 | | mariadb-bin.000005 | 899 | | mariadb-bin.000006 | 125 | | mariadb-bin.000007 | 18907 | | mariadb-bin.000008 | 19530 | | mariadb-bin.000009 | 151 | | mariadb-bin.000010 | 151 | | mariadb-bin.000011 | 125 | | mariadb-bin.000012 | 151 | | mariadb-bin.000013 | 151 | | mariadb-bin.000014 | 125 | | mariadb-bin.000015 | 151 | | mariadb-bin.000016 | 314 | +--------------------+-----------+ URL: https://mariadb.com/kb/en/show-binary-logs/https://mariadb.com/kb/en/show-binary-logs/O#)JSON_SETJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_SET(json_doc, path, val[, path, val] ...) Description ----------- Updates or inserts data into a JSON document, returning the result, or NULL if any of the arguments are NULL or the optional path fails to find an object. An error will occur if the JSON document is invalid, the path is invalid or if the path contains a * or wildcard. JSON_SET can update or insert data, while JSON_REPLACE can only update, and JSON_INSERT only insert. Examples -------- URL: https://mariadb.com/kb/en/json_set/https://mariadb.com/kb/en/json_set/'RJ*Aggregate Functions as Window FunctionsWindow functions were first introduced in MariaDB 10.2.0. It is possible to use aggregate functions as window functions. An aggregate function used as a window function must have the OVER clause. For example, here's COUNT() used as a window function: select COUNT(*) over (order by column) from table; MariaDB currently allows these aggregate functions to be used as window functions: AVG BIT_AND BIT_OR BIT_XOR COUNT MAX MIN STD STDDEV STDDEV_POP STDDEV_SAMP SUM VAR_POP VAR_SAMP VARIANCE URL: https://mariadb.com/kb/en/library/aggregate-functions-as-window-functions/https://mariadb.com/kb/en/library/aggregate-functions-as-window-functions/ $*CUME_DISTThe CUME_DIST() function was first introduced with window functions in MariaDB 10.2.0. Syntax ------ CUME_DIST() OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- CUME_DIST() is a window function that returns the cumulative distribution of a given row. The following formula is used to calculate the value: (number of rows URL: https://mariadb.com/kb/en/cume_dist/https://mariadb.com/kb/en/cume_dist/,[ uT i(QRa-SHOW BINLOG EVENTSSyntax ------ SHOW BINLOG EVENTS [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count] Description ----------- Shows the events in the binary log. If you do not specify 'log_name', the first binary log is displayed. Example SHOW BINLOG EVENTS IN 'mysql_sandbox10019-bin.000002'; +-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | +-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+ | mysql_sandbox10019-bin.000002 | 4 | Format_desc | 1 | 248 | Server ver: 10.0.19-MariaDB-log, Binlog ver: 4 | | mysql_sandbox10019-bin.000002 | 248 | Gtid_list | 1 | 273 | [] | | mysql_sandbox10019-bin.000002 | 273 | Binlog_checkpoint | 1 | 325 | mysql_sandbox10019-bin.000002 | | mysql_sandbox10019-bin.000002 | 325 | Gtid | 1 | 363 | GTID 0-1-1 | | mysql_sandbox10019-bin.000002 | 363 | Query | 1 | 446 | CREATE DATABASE blog | | mysql_sandbox10019-bin.000002 | 446 | Gtid | 1 | 484 | GTID 0-1-2 | | mysql_sandbox10019-bin.000002 | 484 | Query | 1 | 571 | use `blog`; CREATE TABLE bb (id INT) | +-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+ URL: https://mariadb.com/kb/en/show-binlog-events/https://mariadb.com/kb/en/show-binlog-events/bs-SHOW CHARACTER SETSyntax ------ SHOW CHARACTER SET [LIKE 'pattern' | WHERE expr] Description ----------- The SHOW CHARACTER SET statement shows all available character sets. The LIKE clause, if present on its own, indicates which character set names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The same information can be queried from the information_schema.CHARACTER_SETS table. See Setting Character Sets and Collations for details on specifying the character set at the server, database, table and column levels. Examples -------- SHOW CHARACTER SET LIKE 'latin%'; +---------+-----------------------------+-------------------+--------+ | Charset | Description | Default collation | Maxlen | +---------+-----------------------------+-------------------+--------+ | latin1 | cp1252 West European | latin1_swedish_ci | 1 | | latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 | | latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 | | latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 | +---------+-----------------------------+-------------------+--------+ SHOW CHARACTER SET WHERE Maxlen LIKE '2'; +---------+---------------------------+-------------------+--------+ | Charset | Description | Default collation | Maxlen | +---------+---------------------------+-------------------+--------+ | big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 | | sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 | | euckr | EUC-KR Korean | euckr_korean_ci | 2 | | gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 | | gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 | | ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 | | cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 | +---------+---------------------------+-------------------+--------+ URL: https://mariadb.com/kb/en/show-character-set/https://mariadb.com/kb/en/show-character-set/c1SHOW CLIENT_STATISTICSMariaDB 5.2 introduced the User Statistics feature. Syntax ------ SHOW CLIENT_STATISTICS Description ----------- The SHOW CLIENT_STATISTICS statement was introduced in MariaDB 5.2 as part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.CLIENT_STATISTICS table holds statistics about client connections. The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.CLIENT_STATISTICS articles for more information. Example From MariaDB 10.0: SHOW CLIENT_STATISTICS\G *************************** 1. row *************************** Client: localhost Total_connections: 35 Concurrent_connections: 0 Connected_time: 708 Busy_time: 2.5557979999999985 Cpu_time: 0.04123740000000002 Bytes_received: 3883 Bytes_sent: 21595 Binlog_bytes_written: 0 Rows_read: 18 Rows_sent: 115 Rows_deleted: 0 Rows_inserted: 0 Rows_updated: 0 Select_commands: 70 Update_commands: 0 Other_commands: 0 Commit_transactions: 1 Rollback_transactions: 0 Denied_connections: 0 Lost_connections: 0 Access_denied: 0 Empty_queries: 35 URL: https://mariadb.com/kb/en/show-client-statistics/https://mariadb.com/kb/en/show-client-statistics/d9 )SHOW COLLATIONSyntax ------ SHOW COLLATION [LIKE 'pattern' | WHERE expr] Description ----------- The output from SHOW COLLATION includes all available collations. The LIKE clause, if present on its own, indicates which collation names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The same information can be queried from the information_schema.COLLATIONS table. See Setting Character Sets and Collations for details on specifying the collation at the server, database, table and column levels. Examples -------- SHOW COLLATION LIKE 'latin1%'; +-------------------+---------+----+---------+----------+---------+ | Collation | Charset | Id | Default | Compiled | Sortlen | +-------------------+---------+----+---------+----------+---------+ | latin1_german1_ci | latin1 | 5 | | Yes | 1 | | latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 | | latin1_danish_ci | latin1 | 15 | | Yes | 1 | | latin1_german2_ci | latin1 | 31 | | Yes | 2 | | latin1_bin | latin1 | 47 | | Yes | 1 | | latin1_general_ci | latin1 | 48 | | Yes | 1 | | latin1_general_cs | latin1 | 49 | | Yes | 1 | | latin1_spanish_ci | latin1 | 94 | | Yes | 1 | +-------------------+---------+----+---------+----------+---------+ SHOW COLLATION WHERE Sortlen LIKE '8' AND Charset LIKE 'utf8'; +--------------------+---------+-----+---------+----------+---------+ | Collation | Charset | Id | Default | Compiled | Sortlen | +--------------------+---------+-----+---------+----------+---------+ | utf8_unicode_ci | utf8 | 192 | | Yes | 8 | | utf8_icelandic_ci | utf8 | 193 | | Yes | 8 | | utf8_latvian_ci | utf8 | 194 | | Yes | 8 | | utf8_romanian_ci | utf8 | 195 | | Yes | 8 | | utf8_slovenian_ci | utf8 | 196 | | Yes | 8 | | utf8_polish_ci | utf8 | 197 | | Yes | 8 | | utf8_estonian_ci | utf8 | 198 | | Yes | 8 | | utf8_spanish_ci | utf8 | 199 | | Yes | 8 | | utf8_swedish_ci | utf8 | 200 | | Yes | 8 | | utf8_turkish_ci | utf8 | 201 | | Yes | 8 | | utf8_czech_ci | utf8 | 202 | | Yes | 8 | | utf8_danish_ci | utf8 | 203 | | Yes | 8 | | utf8_lithuanian_ci | utf8 | 204 | | Yes | 8 | | utf8_slovak_ci | utf8 | 205 | | Yes | 8 | | utf8_spanish2_ci | utf8 | 206 | | Yes | 8 | | utf8_roman_ci | utf8 | 207 | | Yes | 8 | | utf8_persian_ci | utf8 | 208 | | Yes | 8 | | utf8_esperanto_ci | utf8 | 209 | | Yes | 8 | | utf8_hungarian_ci | utf8 | 210 | | Yes | 8 | | utf8_sinhala_ci | utf8 | 211 | | Yes | 8 | | utf8_croatian_ci | utf8 | 213 | | Yes | 8 | +--------------------+---------+-----+---------+----------+---------+ URL: https://mariadb.com/kb/en/show-collation/https://mariadb.com/kb/en/show-collation/~ r $e 'SHOW COLUMNSSyntax ------ SHOW [FULL] {COLUMNS | FIELDS} FROM tbl_name [FROM db_name] [LIKE 'pattern' | WHERE expr] Description ----------- SHOW COLUMNS displays information about the columns in a given table. It also works for views. The LIKE clause, if present on its own, indicates which column names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. If the data types differ from what you expect them to be based on a CREATE TABLE statement, note that MariaDB sometimes changes data types when you create or alter a table. The conditions under which this occurs are described in the Silent Column Changes article. The FULL keyword causes the output to include the column collation and comments, as well as the privileges you have for each column. You can use db_name.tbl_name as an alternative to the tbl_name FROM db_name syntax. In other words, these two statements are equivalent: SHOW COLUMNS FROM mytable FROM mydb; SHOW COLUMNS FROM mydb.mytable; SHOW COLUMNS displays the following values for each table column: Field indicates the column name. Type indicates the column data type. Collation indicates the collation for non-binary string columns, or NULL for other columns. This value is displayed only if you use the FULL keyword. The Null field contains YES if NULL values can be stored in the column, NO if not. The Key field indicates whether the column is indexed: If Key is empty, the column either is not indexed or is indexed only as a secondary column in a multiple-column, non-unique index. If Key is PRI, the column is a PRIMARY KEY or is one of the columns in a multiple-column PRIMARY KEY. If Key is UNI, the column is the first column of a unique-valued index that cannot contain NULL values. If Key is MUL, multiple occurrences of a given value are allowed within the column. The column is the first column of a non-unique index or a unique-valued index that can contain NULL values. If more than one of the Key values applies to a given column of a table, Key displays the one with the highest priority, in the order PRI, UNI, MUL. A UNIQUE index may be displayed as PRI if it cannot contain NULL values and there is no PRIMARY KEY in the table. A UNIQUE index may display as MUL if several columns form a composite UNIQUE index; although the combination of the columns is unique, each column can still hold multiple occurrences of a given value. The Default field indicates the default value that is assigned to the column. The Extra field contains any additional information that is available about a given column. Value | Description | AUTO_INCREMENT | The column was created with the AUTO_INCREMENT keyword. | PERSISTENT | The column was created with the PERSISTENT keyword. (New in 5.3) | VIRTUAL | The column was created with the VIRTUAL keyword. (New in 5.3) | on update CURRENT_TIMESTAMP | The column is a TIMESTAMP column that is automatically updated on INSERT and UPDATE. | Privileges indicates the privileges you have for the column. This value is displayed only if you use the FULL keyword. Comment indicates any comment the column has. This value is displayed only if you use the FULL keyword. SHOW FIELDS is a synonym for SHOW COLUMNS. Also DESCRIBE and EXPLAIN can be used as shortcuts. You can also list a table's columns with: mysqlshow db_name tbl_name See the mysqlshow command for more details. The DESCRIBE statement provides information similar to SHOW COLUMNS. The information_schema.COLUMNS table provides similar, but more complete, information. The SHOW CREATE TABLE, SHOW TABLE STATUS, and SHOW INDEX statements also provide information about tables. Examples -------- SHOW COLUMNS FROM city; +------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+----------+------+-----+---------+----------------+ | Id | int(11) | NO | PRI | NULL | auto_increment | | Name | char(35) | NO | | | | | Country | char(3) | NO | UNI | | | | District | char(20) | YES | MUL | | | | Population | int(11) | NO | | 0 | | +------------+----------+------+-----+---------+----------------+ SHOW COLUMNS FROM employees WHERE Type LIKE 'Varchar%'; +---------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------------+-------------+------+-----+---------+-------+ | first_name | varchar(30) | NO | MUL | NULL | | | last_name | varchar(40) | NO | | NULL | | | position | varchar(25) | NO | | NULL | | | home_address | varchar(50) | NO | | NULL | | | home_phone | varchar(12) | NO | | NULL | | | employee_code | varchar(25) | NO | UNI | NULL | | +---------------+-------------+------+-----+---------+-------+ URL: https://mariadb.com/kb/en/show-columns/https://mariadb.com/kb/en/show-columns/ $*NTH_VALUEThe NTH_VALUE() function was first introduced with other window functions in MariaDB 10.2. Syntax ------ NTH_VALUE (expr[, num_row]) OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- The NTH_VALUE function returns the value evaluated at row number num_row of the window frame, starting from 1, or NULL if the row does not exist. URL: https://mariadb.com/kb/en/nth_value/https://mariadb.com/kb/en/nth_value/7+SPIDER_FLUSH_TABLE_MON_CACHESyntax ------ SPIDER_FLUSH_TABLE_MON_CACHE() Description ----------- A UDF installed with the Spider Storage Engine, this function is used for refreshing monitoring server information. It returns a value of 1. Examples -------- SELECT SPIDER_FLUSH_TABLE_MON_CACHE(); +--------------------------------+ | SPIDER_FLUSH_TABLE_MON_CACHE() | +--------------------------------+ | 1 | +--------------------------------+ URL: https://mariadb.com/kb/en/spider_flush_table_mon_cache/https://mariadb.com/kb/en/spider_flush_table_mon_cache/ ',COLUMN_CHECKThe COLUMN_CHECK function was added in MariaDB 10.0.1. Syntax ------ COLUMN_CHECK(dyncol_blob); Description ----------- Check if dyncol_blob is a valid packed dynamic columns blob. Return value of 1 means the blob is valid, return value of 0 means it is not. Rationale: Normally, one works with valid dynamic column blobs. Functions like COLUMN_CREATE, COLUMN_ADD, COLUMN_DELETE always return valid dynamic column blobs. However, if a dynamic column blob is accidentally truncated, or transcoded from one character set to another, it will be corrupted. This function can be used to check if a value in a blob field is a valid dynamic column blob. URL: https://mariadb.com/kb/en/column_check/https://mariadb.com/kb/en/column_check/ (,COLUMN_DELETEThe Dynamic columns feature was introduced in MariaDB 5.3. Syntax ------ COLUMN_DELETE(dyncol_blob, column_nr, column_nr...); COLUMN_DELETE(dyncol_blob, column_name, column_name...); Description ----------- Deletes a dynamic column with the specified name. Multiple names can be given. The return value is a dynamic column blob after the modification. URL: https://mariadb.com/kb/en/column_delete/https://mariadb.com/kb/en/column_delete/ (,COLUMN_EXISTSThe Dynamic columns feature was introduced in MariaDB 5.3. Syntax ------ COLUMN_EXISTS(dyncol_blob, column_nr); COLUMN_EXISTS(dyncol_blob, column_name); Description ----------- Checks if a column with name column_name exists in dyncol_blob. If yes, return 1, otherwise return 0. See dynamic columns for more information. URL: https://mariadb.com/kb/en/column_exists/https://mariadb.com/kb/en/column_exists/8SB 6񵄔Ef ,SHOW CONTRIBUTORSSyntax ------ SHOW CONTRIBUTORS Description ----------- The SHOW CONTRIBUTORS statement displays information about the companies and people who financially contribute to MariaDB. For each contributor, it displays Name, Location, and Comment values. All columns are encoded as latin1. In MariaDB 5.5 this is in somewhat random order, and the feature was deprecated. In MariaDB 10.0.5 it was un-deprecated, and since then displays all members and sponsors of the MariaDB Foundation as well as other financial contributors. Example SHOW CONTRIBUTORS; +---------------------+-------------------------------+-------------------------------------------------------------+ | Name | Location | Comment | +---------------------+-------------------------------+-------------------------------------------------------------+ | Booking.com | https://www.booking.com | Founding member, Platinum Sponsor of the MariaDB Foundation | | Alibaba Cloud | https://www.alibabacloud.com/ | Platinum Sponsor of the MariaDB Foundation | | Tencent Cloud | https://cloud.tencent.com | Platinum Sponsor of the MariaDB Foundation | | Microsoft | https://microsoft.com/ | Platinum Sponsor of the MariaDB Foundation | | MariaDB Corporation | https://mariadb.com | Founding member, Platinum Sponsor of the MariaDB Foundation | | Visma | https://visma.com | Gold Sponsor of the MariaDB Foundation | | DBS | https://dbs.com | Gold Sponsor of the MariaDB Foundation | | IBM | https://www.ibm.com | Gold Sponsor of the MariaDB Foundation | | Tencent Games | http://game.qq.com/ | Gold Sponsor of the MariaDB Foundation | | Nexedi | https://www.nexedi.com | Silver Sponsor of the MariaDB Foundation | | Acronis | https://www.acronis.com | Silver Sponsor of the MariaDB Foundation | | Verkkokauppa.com | https://www.verkkokauppa.com | Bronze Sponsor of the MariaDB Foundation | | Virtuozzo | https://virtuozzo.com | Bronze Sponsor of the MariaDB Foundation | | Tencent Game DBA | http://tencentdba.com/about | Bronze Sponsor of the MariaDB Foundation | | Tencent TDSQL | http://tdsql.org | Bronze Sponsor of the MariaDB Foundation | | Percona | https://www.percona.com/ | Bronze Sponsor of the MariaDB Foundation | | Google | USA | Sponsoring encryption, parallel replication and GTID | | Facebook | USA | Sponsoring non-blocking API, LIMIT ROWS EXAMINED etc | | Ronald Bradford | Brisbane, Australia | EFF contribution for UC2006 Auction | | Sheeri Kritzer | Boston, Mass. USA | EFF contribution for UC2006 Auction | | Mark Shuttleworth | London, UK. | EFF contribution for UC2006 Auction | +---------------------+-------------------------------+-------------------------------------------------------------+ URL: https://mariadb.com/kb/en/show-contributors/https://mariadb.com/kb/en/show-contributors/g/SHOW CREATE DATABASESyntax ------ SHOW CREATE {DATABASE | SCHEMA} db_name Description ----------- Shows the CREATE DATABASE statement that creates the given database. SHOW CREATE SCHEMA is a synonym for SHOW CREATE DATABASE. SHOW CREATE DATABASE quotes database names according to the value of the sql_quote_show_create server system variable. Examples -------- SHOW CREATE DATABASE test; +----------+-----------------------------------------------------------------+ | Database | Create Database | +----------+-----------------------------------------------------------------+ | test | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ | +----------+-----------------------------------------------------------------+ SHOW CREATE SCHEMA test; +----------+-----------------------------------------------------------------+ | Database | Create Database | +----------+-----------------------------------------------------------------+ | test | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ | +----------+-----------------------------------------------------------------+ With sql_quote_show_create off: SHOW CREATE DATABASE test; +----------+---------------------------------------------------------------+ | Database | Create Database | +----------+---------------------------------------------------------------+ | test | CREATE DATABASE test /*!40100 DEFAULT CHARACTER SET latin1 */ | +----------+---------------------------------------------------------------+ URL: https://mariadb.com/kb/en/show-create-database/https://mariadb.com/kb/en/show-create-database/h,SHOW CREATE EVENTSyntax ------ SHOW CREATE EVENT event_name Description ----------- This statement displays the CREATE EVENT statement needed to re-create a given event, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection.. To find out which events are present, use SHOW EVENTS. The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719 The information_schema.EVENTS table provides similar, but more complete, information. Examples -------- SHOW CREATE EVENT test.e_daily\G *************************** 1. row *************************** Event: e_daily sql_mode: time_zone: SYSTEM Create Event: CREATE EVENT `e_daily` ON SCHEDULE EVERY 1 DAY STARTS CURRENT_TIMESTAMP + INTERVAL 6 HOUR ON COMPLETION NOT PRESERVE ENABLE COMMENT 'Saves total number of sessions then clears the table each day' DO BEGIN INSERT INTO site_activity.totals (time, total) SELECT CURRENT_TIMESTAMP, COUNT(*) FROM site_activity.sessions; DELETE FROM site_activity.sessions; END character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-create-event/https://mariadb.com/kb/en/show-create-event/ &,COLUMN_LISTThe Dynamic columns feature was introduced in MariaDB 5.3. Syntax ------ COLUMN_LIST(dyncol_blob); Description ----------- Since MariaDB 10.0.1, this function returns a comma-separated list of column names. The names are quoted with backticks. Before MariaDB 10.0.1, it returned a comma-separated list of column numbers, not names. See dynamic columns for more information. URL: https://mariadb.com/kb/en/column_list/https://mariadb.com/kb/en/column_list/aJ X SHOW CREATE FUNCTION VatCents\G *************************** 1. row *************************** Function: VatCents sql_mode: Create Function: CREATE DEFINER=`root`@`localhost` FUNCTION `VatCents`(price DECIMAL(10,2)) RETURNS int(11) DETERMINISTIC BEGIN DECLARE x INT; SET x = price * 114; RETURN x; END character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-create-function/https://mariadb.com/kb/en/show-create-function/j.SHOW CREATE PACKAGEOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ SHOW CREATE PACKAGE [ db_name . ] package_name Description ----------- The SHOW CREATE PACKAGE statement can be used when Oracle SQL_MODE is set. Shows the CREATE statement that creates the given package specification. Examples -------- SHOW CREATE PACKAGE employee_tools\G *************************** 1. row *************************** Package: employee_tools sql_mode: PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER Create Package: CREATE DEFINER="root"@"localhost" PACKAGE "employee_tools" AS FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2); PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)); PROCEDURE raiseSalaryStd(eid INT); PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)); END character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-create-package/https://mariadb.com/kb/en/show-create-package/k03SHOW CREATE PACKAGE BODYOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ SHOW CREATE PACKAGE BODY [ db_name . ] package_name Description ----------- The SHOW CREATE PACKAGE BODY statement can be used when Oracle SQL_MODE is set. Shows the CREATE statement that creates the given package body (i.e. the implementation). Examples -------- SHOW CREATE PACKAGE BODY employee_tools\G *************************** 1. row *************************** Package body: employee_tools sql_mode: PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER Create Package Body: CREATE DEFINER="root"@"localhost" PACKAGE BODY "employee_tools" AS stdRaiseAmount DECIMAL(10,2):=500; PROCEDURE log (eid INT, ecmnt TEXT) AS BEGIN INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt); END; PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS eid INT; BEGIN INSERT INTO employee (name, salary) VALUES (ename, esalary); eid:= last_insert_id(); log(eid, 'hire ' || ename); END; FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS nSalary DECIMAL(10,2); BEGIN SELECT salary INTO nSalary FROM employee WHERE id=eid; log(eid, 'getSalary id=' || eid || ' salary=' || nSalary); RETURN nSalary; END; PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS BEGIN UPDATE employee SET salary=salary+amount WHERE id=eid; log(eid, 'raiseSalary id=' || eid || ' amount=' || amount); END; PROCEDURE raiseSalaryStd(eid INT) AS BEGIN raiseSalary(eid, stdRaiseAmount); log(eid, 'raiseSalaryStd id=' || eid); END; BEGIN log(0, 'Session ' || connection_id() || ' ' || current_user || ' started'); END character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-create-package-body/https://mariadb.com/kb/en/show-create-package-body/l 0SHOW CREATE PROCEDURESyntax ------ SHOW CREATE PROCEDURE proc_name Description ----------- This statement is a MariaDB extension. It returns the exact string that can be used to re-create the named stored procedure, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection.. A similar statement, SHOW CREATE FUNCTION, displays information about stored functions. Both statements require that you are the owner of the routine or have the SELECT privilege on the mysql.proc table. When neither is true, the statements display NULL for the Create Procedure or Create Function field. Warning Users with SELECT privileges on mysql.proc or USAGE privileges on *.* can view the text of routines, even when they do not have privileges for the function or procedure itself. The output of these statements is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719 Examples -------- Here's a comparison of the SHOW CREATE PROCEDURE and SHOW CREATE FUNCTION statements. SHOW CREATE PROCEDURE test.simpleproc\G *************************** 1. row *************************** Procedure: simpleproc sql_mode: Create Procedure: CREATE PROCEDURE `simpleproc`(OUT param1 INT) BEGIN SELECT COUNT(*) INTO param1 FROM t; END character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: latin1_swedish_ci SHOW CREATE FUNCTION test.hello\G *************************** 1. row *************************** Function: hello sql_mode: Create Function: CREATE FUNCTION `hello`(s CHAR(20)) RETURNS CHAR(50) RETURN CONCAT('Hello, ',s,'!') character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: latin1_swedish_ci When the user issuing the statement does not have privileges on the routine, attempting to CALL the procedure raises Error 1370. CALL test.prc1(); Error 1370 (42000): execute command denieed to user 'test_user'@'localhost' for routine 'test'.'prc1' If the user neither has privilege to the routine nor the SELECT privilege on mysql.proc table, it raises Error 1305, informing them that the procedure does not exist. SHOW CREATE TABLES test.prc1\G Error 1305 (42000): PROCEDURE prc1 does not exist URL: https://mariadb.com/kb/en/show-create-procedure/https://mariadb.com/kb/en/show-create-procedure/Er }? q/ m]/SHOW CREATE SEQUENCESequences were introduced in MariaDB 10.3. Syntax ------ SHOW CREATE SEQUENCE sequence_name; Description ----------- Shows the CREATE SEQUENCE statement that created the given sequence. The statement requires the SELECT privilege for the table. Example CREATE SEQUENCE s1 START WITH 50; SHOW CREATE SEQUENCE s1\G; *************************** 1. row *************************** Table: t1 Create Table: CREATE SEQUENCE `s1` start with 50 minvalue 1 maxvalue 9223372036854775806 increment by 1 cache 1000 nocycle ENGINE=Aria Notes If you want to see the underlying table structure used for the SEQUENCE you can use SHOW CREATE TABLE on the SEQUENCE. You can also use SELECT to read the current recorded state of the SEQUENCE: CREATE SEQUENCE t1; SHOW CREATE TABLE s1\G *************************** 1. row *************************** Table: s1 Create Table: CREATE TABLE `s1` ( `next_value` bigint(21) NOT NULL COMMENT 'next not cached value', `min_value` bigint(21) NOT NULL COMMENT 'min value', `max_value` bigint(21) NOT NULL COMMENT 'max value', `start` bigint(21) NOT NULL COMMENT 'start value', `increment` bigint(21) NOT NULL COMMENT 'increment value', `cache` bigint(21) NOT NULL COMMENT 'cache size', `cycle` tinyint(1) unsigned NOT NULL COMMENT 'cycle state', `round` bigint(21) NOT NULL COMMENT 'How many cycles has been done' ) ENGINE=Aria SEQUENCE=1 SELECT * FROM s1; +------------+-----------+---------------------+-------+-----------+-------+-------+-------+ | next_value | min_value | max_value | start | increment | cache | cycle | round | +------------+-----------+---------------------+-------+-----------+-------+-------+-------+ | 1 | 1 | 9223372036854775806 | 1 | 1 | 1000 | 0 | 0 | +------------+-----------+---------------------+-------+-----------+-------+-------+-------+ URL: https://mariadb.com/kb/en/show-create-sequence/https://mariadb.com/kb/en/show-create-sequence/n ,SHOW CREATE TABLESyntax ------ SHOW CREATE TABLE tbl_name Description ----------- Shows the CREATE TABLE statement that created the given table. The statement requires the SELECT privilege for the table. This statement also works with views and SEQUENCE. SHOW CREATE TABLE quotes table and column names according to the value of the sql_quote_show_create server system variable. MariaDB and MySQL-specific table options, column options, and index options are not included in the output of this statement if the NO_TABLE_OPTIONS, NO_FIELD_OPTIONS and NO_KEY_OPTIONS SQL_MODE flags are used. Invalid table options, column options and index options are normally commented out (note, that it is possible to create a table with invalid options, by altering a table of a different engine, where these options were valid). To have them uncommented, enable IGNORE_BAD_TABLE_OPTIONS SQL_MODE. Remember that replaying a CREATE TABLE statement with uncommented invalid options will fail with an error, unless IGNORE_BAD_TABLE_OPTIONS SQL_MODE is in effect. Note that SHOW CREATE TABLE is not meant to provide metadata about a table. It provides information about how the table was declared, but the real table structure could differ a bit. For example, if an index has been declared as HASH, the CREATE TABLE statement returned by SHOW CREATE TABLE will declare that index as HASH; however, it is possible that the index is in fact a BTREE, because the storage engine does not support HASH. MariaDB 10.2.1 permits TEXT and BLOB data types to be assigned a DEFAULT value. As a result, from MariaDB 10.2.1, SHOW CREATE TABLE will append a DEFAULT NULL to nullable TEXT or BLOB fields if no specific default is provided. From MariaDB 10.2.2, numbers are no longer quoted in the DEFAULT clause in SHOW CREATE statement. Previously, MariaDB quoted numbers. Examples -------- SHOW CREATE TABLE t\G *************************** 1. row *************************** Table: t Create Table: CREATE TABLE `t` ( `id` int(11) NOT NULL AUTO_INCREMENT, `s` char(60) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 With sql_quote_show_create off: SHOW CREATE TABLE t\G *************************** 1. row *************************** Table: t Create Table: CREATE TABLE t ( id int(11) NOT NULL AUTO_INCREMENT, s char(60) DEFAULT NULL, PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 Unquoted numeric DEFAULTs, from MariaDB 10.2.2: CREATE TABLE td (link TINYINT DEFAULT 1); SHOW CREATE TABLE td\G *************************** 1. row *************************** Table: td Create Table: CREATE TABLE `td` ( `link` tinyint(4) DEFAULT 1 ) ENGINE=InnoDB DEFAULT CHARSET=latin1 Quoted numeric DEFAULTs, until MariaDB 10.2.1: CREATE TABLE td (link TINYINT DEFAULT 1); SHOW CREATE TABLE td\G *************************** 1. row *************************** Table: td Create Table: CREATE TABLE `td` ( `link` tinyint(4) DEFAULT '1' ) ENGINE=InnoDB DEFAULT CHARSET=latin1 URL: https://mariadb.com/kb/en/show-create-table/https://mariadb.com/kb/en/show-create-table/. 3@o.SHOW CREATE TRIGGERSyntax ------ SHOW CREATE TRIGGER trigger_name Description ----------- This statement shows a CREATE TRIGGER statement that creates the given trigger, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection. The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719 Examples -------- SHOW CREATE TRIGGER example\G *************************** 1. row *************************** Trigger: example sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,STRICT_ALL_TABLES ,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ ENGINE_SUBSTITUTION SQL Original Statement: CREATE DEFINER=`root`@`localhost` TRIGGER example BEFORE INSERT ON t FOR EACH ROW BEGIN SET NEW.c = NEW.c * 2; END character_set_client: cp850 collation_connection: cp850_general_ci Database Collation: utf8_general_ci Created: 2016-09-29 13:53:34.35 The Created column was added in MySQL 5.7 and MariaDB 10.2.3 as part of introducing multiple trigger events per action. URL: https://mariadb.com/kb/en/show-create-trigger/https://mariadb.com/kb/en/show-create-trigger/p5+SHOW CREATE USERSHOW CREATE USER was introduced in MariaDB 10.2.0 Syntax ------ SHOW CREATE USER user_name Description ----------- Shows the CREATE USER statement that created the given user. The statement requires the SELECT privilege for the mysql database, except for the current user. Examples -------- CREATE USER foo4@test require cipher 'text' issuer 'foo_issuer' subject 'foo_subject'; SHOW CREATE USER foo4@test\G *************************** 1. row *************************** CREATE USER 'foo4'@'test' REQUIRE ISSUER 'foo_issuer' SUBJECT 'foo_subject' CIPHER 'text' User Password Expiry: CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY; SHOW CREATE USER 'monty'@'localhost'; +------------------------------------------------------------------+ | CREATE USER for monty@localhost | +------------------------------------------------------------------+ | CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY | +------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/show-create-user/https://mariadb.com/kb/en/show-create-user/q+SHOW CREATE VIEWSyntax ------ SHOW CREATE VIEW view_name Description ----------- This statement shows a CREATE VIEW statement that creates the given view, as well as the character set used by the connection when the view was created. This statement also works with views. SHOW CREATE VIEW quotes table, column and stored function names according to the value of the sql_quote_show_create server system variable. Examples -------- SHOW CREATE VIEW example\G *************************** 1. row *************************** View: example Create View: CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `example` AS (select `t`.`id` AS `id`,`t`.`s` AS `s` from `t`) character_set_client: cp850 collation_connection: cp850_general_ci With sql_quote_show_create off: SHOW CREATE VIEW example\G *************************** 1. row *************************** View: example Create View: CREATE ALGORITHM=UNDEFINED DEFINER=root@localhost SQL SECU RITY DEFINER VIEW example AS (select t.id AS id,t.s AS s from t) character_set_client: cp850 collation_connection: cp850_general_ci URL: https://mariadb.com/kb/en/show-create-view/https://mariadb.com/kb/en/show-create-view/rB)SHOW DATABASESSyntax ------ SHOW {DATABASES | SCHEMAS} [LIKE 'pattern' | WHERE expr] Description ----------- SHOW DATABASES lists the databases on the MariaDB server host. SHOW SCHEMAS is a synonym for SHOW DATABASES. The LIKE clause, if present on its own, indicates which database names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. You see only those databases for which you have some kind of privilege, unless you have the global SHOW DATABASES privilege. You can also get this list using the mysqlshow command. If the server was started with the --skip-show-database option, you cannot use this statement at all unless you have the SHOW DATABASES privilege. Example SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | test | +--------------------+ SHOW DATABASES LIKE 'm%'; +---------------+ | Database (m%) | +---------------+ | mysql | +---------------+ URL: https://mariadb.com/kb/en/show-databases/https://mariadb.com/kb/en/show-databases/u  'SHOW ENGINESSyntax ------ SHOW [STORAGE] ENGINES Description ----------- SHOW ENGINES displays status information about the server's storage engines. This is particularly useful for checking whether a storage engine is supported, or to see what the default engine is. SHOW TABLE TYPES is a deprecated synonym. The information_schema.ENGINES table provides the same information. Since storage engines are plugins, different information about them is also shown in the information_schema.PLUGINS table and by the SHOW PLUGINS statement. Note that both MySQL's InnoDB and Percona's XtraDB replacement are labeled as InnoDB. However, if XtraDB is in use, it will be specified in the COMMENT field. See XtraDB and InnoDB. The same applies to FederatedX. The output consists of the following columns: Engine indicates the engine's name. Support indicates whether the engine is installed, and whether it is the default engine for the current session. Comment is a brief description. Transactions, XA and Savepoints indicate whether transactions, XA transactions and transaction savepoints are supported by the engine. Examples -------- SHOW ENGINES\G *************************** 1. row *************************** Engine: InnoDB Support: DEFAULT Comment: Supports transactions, row-level locking, and foreign keys Transactions: YES XA: YES Savepoints: YES *************************** 2. row *************************** Engine: CSV Support: YES Comment: CSV storage engine Transactions: NO XA: NO Savepoints: NO *************************** 3. row *************************** Engine: MyISAM Support: YES Comment: MyISAM storage engine Transactions: NO XA: NO Savepoints: NO *************************** 4. row *************************** Engine: BLACKHOLE Support: YES Comment: /dev/null storage engine (anything you write to it disappears) Transactions: NO XA: NO Savepoints: NO *************************** 5. row *************************** Engine: FEDERATED Support: YES Comment: FederatedX pluggable storage engine Transactions: YES XA: NO Savepoints: YES *************************** 6. row *************************** Engine: MRG_MyISAM Support: YES Comment: Collection of identical MyISAM tables Transactions: NO XA: NO Savepoints: NO *************************** 7. row *************************** Engine: ARCHIVE Support: YES Comment: Archive storage engine Transactions: NO XA: NO Savepoints: NO *************************** 8. row *************************** Engine: MEMORY Support: YES Comment: Hash based, stored in memory, useful for temporary tables Transactions: NO XA: NO Savepoints: NO *************************** 9. row *************************** Engine: PERFORMANCE_SCHEMA Support: YES Comment: Performance Schema Transactions: NO XA: NO Savepoints: NO *************************** 10. row *************************** Engine: Aria Support: YES Comment: Crash-safe tables with MyISAM heritage Transactions: NO XA: NO Savepoints: NO 10 rows in set (0.00 sec) URL: https://mariadb.com/kb/en/show-engines/https://mariadb.com/kb/en/show-engines/I Lw ~ 䶼n s &SHOW ENGINESyntax ------ SHOW ENGINE engine_name {STATUS | MUTEX} Description ----------- SHOW ENGINE displays operational information about a storage engine. The following statements currently are supported: SHOW ENGINE INNODB STATUS SHOW ENGINE INNODB MUTEX SHOW ENGINE PERFORMANCE_SCHEMA STATUS If the Sphinx Storage Engine is installed, the following is also supported: SHOW ENGINE SPHINX STATUS See SHOW ENGINE SPHINX STATUS. Older (and now removed) synonyms were SHOW INNODB STATUS for SHOW ENGINE INNODB STATUS and SHOW MUTEX STATUS for SHOW ENGINE INNODB MUTEX. SHOW ENGINE BDB LOGS formerly displayed status information about BDB log files. It was deprecated in MySQL 5.1.12 and removed in MariaDB and MySQL 5.5, so now produces an error. SHOW ENGINE INNODB STATUS SHOW ENGINE INNODB STATUS displays extensive information from the standard InnoDB Monitor about the state of the InnoDB storage engine. See SHOW ENGINE INNODB STATUS for more. SHOW ENGINE INNODB MUTEX SHOW ENGINE INNODB MUTEX displays InnoDB mutex statistics. The statement displays the following output fields: Type: Always InnoDB. Name: The source file where the mutex is implemented, and the line number in the file where the mutex is created. The line number is dependent on the MariaDB version. Status: This field displays the following values if UNIV_DEBUG was defined at compilation time (for example, in include/univ.h in the InnoDB part of the source tree). Only the os_waits value is displayed if UNIV_DEBUG was not defined. Without UNIV_DEBUG, the information on which the output is based is insufficient to distinguish regular mutexes and mutexes that protect rw-locks (which allow multiple readers or a single writer). Consequently, the output may appear to contain multiple rows for the same mutex. count indicates how many times the mutex was requested. spin_waits indicates how many times the spinlock had to run. spin_rounds indicates the number of spinlock rounds. (spin_rounds divided by spin_waits provides the average round count.) os_waits indicates the number of operating system waits. This occurs when the spinlock did not work (the mutex was not locked during the spinlock and it was necessary to yield to the operating system and wait). os_yields indicates the number of times a the thread trying to lock a mutex gave up its timeslice and yielded to the operating system (on the presumption that allowing other threads to run will free the mutex so that it can be locked). os_wait_times indicates the amount of time (in ms) spent in operating system waits, if the timed_mutexes system variable is 1 (ON). If timed_mutexes is 0 (OFF), timing is disabled, so os_wait_times is 0. timed_mutexes is off by default. Information from this statement can be used to diagnose system problems. For example, large values of spin_waits and spin_rounds may indicate scalability problems. The information_schema.INNODB_MUTEXES table provides similar information. SHOW ENGINE PERFORMANCE_SCHEMA STATUS This statement shows how much memory is used for performance_schema tables and internal buffers. The output contains the following fields: Type: Always performance_schema. Name: The name of a table, the name of an internal buffer, or the performance_schema word, followed by a dot and an attribute. Internal buffers names are enclosed by parenthesis. performance_schema means that the attribute refers to the whole database (it is a total). Status: The value for the attribute. The following attributes are shown, in this order, for all tables: row_size: The memory used for an individual record. This value will never change. row_count: The number of rows in the table or buffer. For some tables, this value depends on a server system variable. memory: For tables and performance_schema, this is the result of row_size * row_count. For internal buffers, the attributes are: count size URL: https://mariadb.com/kb/en/show-engine/https://mariadb.com/kb/en/show-engine/v &SHOW ERRORSSyntax ------ SHOW ERRORS [LIMIT [offset,] row_count] SHOW ERRORS [LIMIT row_count OFFSET offset] SHOW COUNT(*) ERRORS Description ----------- This statement is similar to SHOW WARNINGS, except that instead of displaying errors, warnings, and notes, it displays only errors. The LIMIT clause has the same syntax as for the SELECT statement. The SHOW COUNT(*) ERRORS statement displays the number of errors. You can also retrieve this number from the error_count variable. SHOW COUNT(*) ERRORS; SELECT @@error_count; The value of error_count might be greater than the number of messages displayed by SHOW WARNINGS if the max_error_count system variable is set so low that not all messages are stored. For a list of MariaDB error codes, see MariaDB Error Codes. Examples -------- SELECT f(); ERROR 1305 (42000): FUNCTION f does not exist SHOW COUNT(*) ERRORS; +-----------------------+ | @@session.error_count | +-----------------------+ | 1 | +-----------------------+ SHOW ERRORS; +-------+------+---------------------------+ | Level | Code | Message | +-------+------+---------------------------+ | Error | 1305 | FUNCTION f does not exist | +-------+------+---------------------------+ URL: https://mariadb.com/kb/en/show-errors/https://mariadb.com/kb/en/show-errors/9 3tRt?4SHOW ENGINE INNODB STATUSSHOW ENGINE INNODB STATUS is a specific form of the SHOW ENGINE statement that displays the InnoDB Monitor output, which is extensive InnoDB information which can be useful in diagnosing problems. The following sections are displayed Status: Shows the timestamp, monitor name and the number of seconds, or the elapsed time between the current time and the time the InnoDB Monitor output was last displayed. The per-second averages are based upon this time. BACKGROUND THREAD: srv_master_thread lines show work performed by the main background thread. SEMAPHORES: Threads waiting for a semaphore and stats on how the number of times threads have needed a spin or a wait on a mutex or rw-lock semaphore. If this number of threads is large, there may be I/O or contention issues. Reducing the size of the innodb_thread_concurrency system variable may help if contention is related to thread scheduling. Spin rounds per wait shows the number of spinlock rounds per OS wait for a mutex. LATEST FOREIGN KEY ERROR: Only shown if there has been a foreign key constraint error, it displays the failed statement and information about the constraint and the related tables. LATEST DETECTED DEADLOCK: Only shown if there has been a deadlock, it displays the transactions involved in the deadlock and the statements being executed, held and required locked and the transaction rolled back to. TRANSACTIONS: The output of this section can help identify lock contention, as well as reasons for the deadlocks. FILE I/O: InnoDB thread information as well as pending I/O operations and I/O performance statistics. INSERT BUFFER AND ADAPTIVE HASH INDEX: InnoDB insert buffer and adaptive hash index status information, including the number of each type of operation performed, and adaptive hash index performance. LOG: InnoDB log information, including current log sequence number, how far the log has been flushed to disk, the position at which InnoDB last took a checkpoint, pending writes and write performance statistics. BUFFER POOL AND MEMORY: Information on buffer pool pages read and written, which allows you to see the number of data file I/O operations performed by your queries. See InnoDB Buffer Pool for more. Similar information is also available from the INFORMATION_SCHEMA.INNODB_BUFFER_POOL_STATS table. ROW OPERATIONS:Information about the main thread, including the number and performance rate for each type of row operation. If the innodb_status_output_locks system variable is set to 1, extended lock information will be displayed. Example output: ===================================== 2016-09-12 04:42:15 7f226145fb00 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 29 seconds ----------------- BACKGROUND THREAD ----------------- srv_master_thread loops: 0 srv_active, 0 srv_shutdown, 527 srv_idle srv_master_thread log flush and writes: 527 ---------- SEMAPHORES ---------- OS WAIT ARRAY INFO: reservation count 4 OS WAIT ARRAY INFO: signal count 4 Mutex spin waits 2, rounds 60, OS waits 2 RW-shared spins 2, rounds 60, OS waits 2 RW-excl spins 0, rounds 0, OS waits 0 Spin rounds per wait: 30.00 mutex, 30.00 RW-shared, 0.00 RW-excl ------------ TRANSACTIONS ------------ Trx id counter 2308 Purge done for trx's n:o < 0 undo n:o < 0 state: running but idle History list length 0 LIST OF TRANSACTIONS FOR EACH SESSION: ---TRANSACTION 0, not started MySQL thread id 3, OS thread handle 0x7f226145fb00, query id 4 localhost root init SHOW ENGINE INNODB STATUS -------- FILE I/O -------- I/O thread 0 state: waiting for completed aio requests (insert buffer thread) I/O thread 1 state: waiting for completed aio requests (log thread) I/O thread 2 state: waiting for completed aio requests (read thread) I/O thread 3 state: waiting for completed aio requests (read thread) I/O thread 4 state: waiting for completed aio requests (read thread) I/O thread 5 state: waiting for completed aio requests (read thread) I/O thread 6 state: waiting for completed aio requests (write thread) I/O thread 7 state: waiting for completed aio requests (write thread) I/O thread 8 state: waiting for completed aio requests (write thread) I/O thread 9 state: waiting for completed aio requests (write thread) Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0, 0, 0, 0] , ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0 Pending flushes (fsync) log: 0; buffer pool: 0 172 OS file reads, 5 OS file writes, 5 OS fsyncs 0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s ------------------------------------- INSERT BUFFER AND ADAPTIVE HASH INDEX ------------------------------------- Ibuf: size 1, free list len 0, seg size 2, 0 merges merged operations: insert 0, delete mark 0, delete 0 discarded operations: insert 0, delete mark 0, delete 0 0.00 hash searches/s, 0.00 non-hash searches/s --- LOG --- Log sequence number 1616829 Log flushed up to 1616829 Pages flushed up to 1616829 Last checkpoint at 1616829 Max checkpoint age 80826164 Checkpoint age target 78300347 Modified age 0 Checkpoint age 0 0 pending log writes, 0 pending chkp writes 8 log i/o's done, 0.00 log i/o's/second ---------------------- BUFFER POOL AND MEMORY ---------------------- Total memory allocated 140771328; in additional pool allocated 0 Total memory allocated by read views 88 Internal hash tables (constant factor + variable factor) Adaptive hash index 2217568 (2213368 + 4200) Page hash 139112 (buffer pool 0 only) Dictionary cache 630703 (554768 + 75935) File system 817648 (812272 + 5376) Lock system 333232 (332872 + 360) Recovery system 0 (0 + 0) Dictionary memory allocated 75935 Buffer pool size 8191 Buffer pool size, bytes 134201344 Free buffers 8037 Database pages 154 Old database pages 0 Modified db pages 0 Percent of dirty pages(LRU & free pages): 0.000 Max dirty pages percent: 75.000 Pending reads 0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 0, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 154, created 0, written 1 0.00 reads/s, 0.00 creates/s, 0.00 writes/s No buffer pool page gets since the last printout Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 154, unzip_LRU len: 0 I/O sum[0]:cur[0], unzip sum[0]:cur[0] -------------- ROW OPERATIONS -------------- 0 queries inside InnoDB, 0 queries in queue 0 read views open inside InnoDB 0 RW transactions active inside InnoDB 0 RO transactions active inside InnoDB 0 out of 1000 descriptors used Main thread process no. 3337, id 139784957703936, state: sleeping Number of rows inserted 0, updated 0, deleted 0, read 0 0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s Number of system rows inserted 0, updated 0, deleted 0, read 0 0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s ---------------------------- END OF INNODB MONITOR OUTPUT ============================ URL: https://mariadb.com/kb/en/show-engine-innodb-status/https://mariadb.com/kb/en/show-engine-innodb-status/ Fw q&SHOW EVENTSSyntax ------ SHOW EVENTS [{FROM | IN} schema_name] [LIKE 'pattern' | WHERE expr] Description ----------- Shows information about Event Manager events (created with CREATE EVENT). Requires the EVENT privilege. Without any arguments, SHOW EVENTS lists all of the events in the current schema: SELECT CURRENT_USER(), SCHEMA(); +----------------+----------+ | CURRENT_USER() | SCHEMA() | +----------------+----------+ | jon@ghidora | myschema | +----------------+----------+ SHOW EVENTS\G *************************** 1. row *************************** Db: myschema Name: e_daily Definer: jon@ghidora Time zone: SYSTEM Type: RECURRING Execute at: NULL Interval value: 10 Interval field: SECOND Starts: 2006-02-09 10:41:23 Ends: NULL Status: ENABLED Originator: 0 character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: latin1_swedish_ci To see the event action, use SHOW CREATE EVENT instead, or look at the information_schema.EVENTS table. To see events for a specific schema, use the FROM clause. For example, to see events for the test schema, use the following statement: SHOW EVENTS FROM test; The LIKE clause, if present, indicates which event names to match. The WHERE clause can be given to select rows using more general conditions, as discussed in Extended Show. URL: https://mariadb.com/kb/en/show-events/https://mariadb.com/kb/en/show-events/x  'SHOW EXPLAINThe SHOW EXPLAIN command is a new feature in MariaDB 10.0.0. Command description The SHOW EXPLAIN command allows one to get an EXPLAIN (that is, a description of a query plan) of a query running in a certain thread. The syntax is: SHOW EXPLAIN FOR ; which will produce an EXPLAIN output for the query that thread number thread_id is running. The thread id can be obtained with SHOW PROCESSLIST. SHOW EXPLAIN FOR 1; +------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+ | 1 | SIMPLE | tbl | index | NULL | a | 5 | NULL | 1000107 | Using index | +------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+ 1 row in set, 1 warning (0.00 sec) The output is always accompanied with a warning which shows the query the target thread is running (this shows what the EXPLAIN is for): SHOW WARNINGS; +-------+------+------------------------+ | Level | Code | Message | +-------+------+------------------------+ | Note | 1003 | select sum(a) from tbl | +-------+------+------------------------+ 1 row in set (0.00 sec) Possible errors The output can be only produced if the target thread is currently running a query, which has a ready query plan. If this is not the case, the output will be: SHOW EXPLAIN FOR 2; ERROR 1932 (HY000): Target is not running an EXPLAINable command You will get this error when: the target thread is not running a command for which one can run EXPLAIN the target thread is running a command for which one can run EXPLAIN, but there is no query plan yet (for example, tables are open and locks are acquired before the query plan is produced) Differences between SHOW EXPLAIN and EXPLAIN outputs Background In MySQL, EXPLAIN execution takes a slightly different route from the way the real query (typically the SELECT) is optimized. This is unfortunate, and has caused a number of bugs in EXPLAIN. (For example, see MDEV-326, MDEV-410, and lp:1013343. lp:992942 is not directly about EXPLAIN, but it also would not have existed if MySQL didn't try to delete parts of a query plan in the middle of the query) SHOW EXPLAIN examines a running SELECT, and hence its output may be slightly different from what EXPLAIN SELECT would produce. We did our best to make sure that either the difference is negligible, or SHOW EXPLAIN's output is closer to reality than EXPLAIN's output. List of recorded differences SHOW EXPLAIN may have Extra='no matching row in const table', where EXPLAIN would produce Extra='Impossible WHERE ...' For queries with subqueries, SHOW EXPLAIN may print select_type==PRIMARY where regular EXPLAIN used to print select_type==SIMPLE, or vice versa. Required permissions Running SHOW EXPLAIN requires the same permissions as running SHOW PROCESSLIST would. URL: https://mariadb.com/kb/en/show-explain/https://mariadb.com/kb/en/show-explain/z/SHOW FUNCTION STATUSSyntax ------ SHOW FUNCTION STATUS [LIKE 'pattern' | WHERE expr] Description ----------- This statement is similar to SHOW PROCEDURE STATUS but for stored functions. The LIKE clause, if present on its own, indicates which function names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The information_schema.ROUTINES table contains more detailed information. Examples -------- Showing all stored functions: SHOW FUNCTION STATUS\G *************************** 1. row *************************** Db: test Name: VatCents Type: FUNCTION Definer: root@localhost Modified: 2013-06-01 12:40:31 Created: 2013-06-01 12:40:31 Security_type: DEFINER Comment: character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci Stored functions whose name starts with 'V': SHOW FUNCTION STATUS LIKE 'V%' \G *************************** 1. row *************************** Db: test Name: VatCents Type: FUNCTION Definer: root@localhost Modified: 2013-06-01 12:40:31 Created: 2013-06-01 12:40:31 Security_type: DEFINER Comment: character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci Stored functions with a security type of 'DEFINER': SHOW FUNCTION STATUS WHERE Security_type LIKE 'DEFINER' \G *************************** 1. row *************************** Db: test Name: VatCents Type: FUNCTION Definer: root@localhost Modified: 2013-06-01 12:40:31 Created: 2013-06-01 12:40:31 Security_type: DEFINER Comment: character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-function-status/https://mariadb.com/kb/en/show-function-status/KB `{ &SHOW GRANTSUsers Syntax ------ SHOW GRANTS [FOR user] Description ----------- This statement lists the GRANT statement or statements that must be issued to duplicate the privileges that are granted to a MariaDB user account. The account is named using the same format as for the GRANT statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For additional information about specifying account names, see GRANT. SHOW GRANTS FOR 'root'@'localhost'; +---------------------------------------------------------------------+ | Grants for root@localhost | +---------------------------------------------------------------------+ | GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION | +---------------------------------------------------------------------+ To list the privileges granted to the account that you are using to connect to the server, you can use any of the following statements: SHOW GRANTS; SHOW GRANTS FOR CURRENT_USER; SHOW GRANTS FOR CURRENT_USER(); If SHOW GRANTS FOR CURRENT_USER (or any of the equivalent syntaxes) is used in DEFINER context (such as within a stored procedure that is defined with SQL SECURITY DEFINER), the grants displayed are those of the definer and not the invoker. Note that the DELETE HISTORY privilege, introduced in MariaDB 10.3.4, is displayed as DELETE VERSIONING ROWS when running SHOW GRANTS (MDEV-17655). Roles Roles were introduced in MariaDB 10.0.5. Syntax ------ SHOW GRANTS [FOR role] Description ----------- From MariaDB 10.0.5, SHOW GRANTS can also be used to view the privileges granted to a role. Example SHOW GRANTS FOR journalist; +------------------------------------------+ | Grants for journalist | +------------------------------------------+ | GRANT USAGE ON *.* TO 'journalist' | | GRANT DELETE ON `test`.* TO 'journalist' | +------------------------------------------+ URL: https://mariadb.com/kb/en/show-grants/https://mariadb.com/kb/en/show-grants/| %SHOW INDEXSyntax ------ SHOW {INDEX | INDEXES | KEYS} FROM tbl_name [FROM db_name] [WHERE expr] Description ----------- SHOW INDEX returns table index information. The format resembles that of the SQLStatistics call in ODBC. You can use db_name.tbl_name as an alternative to the tbl_name FROM db_name syntax. These two statements are equivalent: SHOW INDEX FROM mytable FROM mydb; SHOW INDEX FROM mydb.mytable; SHOW KEYS and SHOW INDEXES are synonyms for SHOW INDEX. You can also list a table's indexes with the following command: mysqlshow -k db_name tbl_name See mysqlshow for more details. The information_schema.STATISTICS table stores similar information. The following fields are returned by SHOW INDEX. Field | Description | Table | Table name | Non_unique | 1 if the index permits duplicate values, 0 if values must be unique. | Key_name | Index name. The primary key is always named PRIMARY. | Seq_in_index | The column's sequence in the index, beginning with 1. | Column_name | Column name. | Collation | Either A, if the column is sorted in ascending order in the index, or NULL if it's not sorted. | Cardinality | Estimated number of unique values in the index. The cardinality statistics are calculated at various times, and can help the optimizer make improved decisions. | Sub_part | NULL if the entire column is included in the index, or the number of included characters if not. | Packed | NULL if the index is not packed, otherwise how the index is packed. | Null | NULL if NULL values are permitted in the column, an empty string if NULL's are not permitted. | Index_type | The index type, which can be BTREE, FULLTEXT, HASH or RTREE. See Storage Engine Index Types. | Comment | Other information, such as whether the index is disabled. | Index_comment | Contents of the COMMENT attribute when the index was created. | The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. Examples -------- CREATE TABLE IF NOT EXISTS `employees_example` ( `id` int(11) NOT NULL AUTO_INCREMENT, `first_name` varchar(30) NOT NULL, `last_name` varchar(40) NOT NULL, `position` varchar(25) NOT NULL, `home_address` varchar(50) NOT NULL, `home_phone` varchar(12) NOT NULL, `employee_code` varchar(25) NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `employee_code` (`employee_code`), KEY `first_name` (`first_name`,`last_name`) ) ENGINE=Aria; INSERT INTO `employees_example` (`first_name`, `last_name`, `position`, `home_address`, `home_phone`, `employee_code`) VALUES ('Mustapha', 'Mond', 'Chief Executive Officer', '692 Promiscuous Plaza', '326-555-3492', 'MM1'), ('Henry', 'Foster', 'Store Manager', '314 Savage Circle', '326-555-3847', 'HF1'), ('Bernard', 'Marx', 'Cashier', '1240 Ambient Avenue', '326-555-8456', 'BM1'), ('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy Boulevard', '328-555-2349', 'LC1'), ('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky Lane', '326-555-6329', 'FC1'), ('Helmholtz', 'Watson', 'Janitor', '944 Soma Court', '329-555-2478', 'HW1'); SHOW INDEXES FROM employees_example; +-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | employees_example | 0 | PRIMARY | 1 | id | A | 7 | NULL | NULL | | BTREE | | | | employees_example | 0 | employee_code | 1 | employee_code | A | 7 | NULL | NULL | | BTREE | | | | employees_example | 1 | first_name | 1 | first_name | A | NULL | NULL | NULL | | BTREE | | | | employees_example | 1 | first_name | 2 | last_name | A | NULL | NULL | NULL | | BTREE | | | +-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ URL: https://mariadb.com/kb/en/show-index/https://mariadb.com/kb/en/show-index/ 8&l } 'SHOW LOCALESSHOW LOCALES was introduced as part of the Information Schema plugin extension in MariaDB 10.1.1. SHOW LOCALES is used to return locales information as part of the Locales plugin. While the information_schema.LOCALES table has 8 columns, the SHOW LOCALES statement will only display 4 of them: Example SHOW LOCALES; +-----+-------+-------------------------------------+------------------------+ | Id | Name | Description | Error_Message_Language | +-----+-------+-------------------------------------+------------------------+ | 0 | en_US | English - United States | english | | 1 | en_GB | English - United Kingdom | english | | 2 | ja_JP | Japanese - Japan | japanese | | 3 | sv_SE | Swedish - Sweden | swedish | ... URL: https://mariadb.com/kb/en/show-locales/https://mariadb.com/kb/en/show-locales/~F-SHOW MASTER STATUSSyntax ------ SHOW MASTER STATUS Description ----------- Provides status information about the binary log files of the master. This statement requires the SUPER or the REPLICATION_CLIENT privilege. To see information about the current GTIDs in the binary log, use the gtid_binlog_pos variable. Example SHOW MASTER STATUS; +--------------------+----------+--------------+------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | +--------------------+----------+--------------+------------------+ | mariadb-bin.000016 | 475 | | | +--------------------+----------+--------------+------------------+ SELECT @@global.gtid_binlog_pos; +--------------------------+ | @@global.gtid_binlog_pos | +--------------------------+ | 0-1-2 | +--------------------------+ URL: https://mariadb.com/kb/en/show-master-status/https://mariadb.com/kb/en/show-master-status/o+SHOW OPEN TABLESSyntax ------ SHOW OPEN TABLES [FROM db_name] [LIKE 'pattern' | WHERE expr] Description ----------- SHOW OPEN TABLES lists the non-TEMPORARY tables that are currently open in the table cache. See http://dev.mysql.com/doc/refman/5.1/en/table-cache.html. The FROM and LIKE clauses may be used. The FROM clause, if present, restricts the tables shown to those present in the db_name database. The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The following information is returned: Column | Description | Database | Database name. | Name | Table name. | In_use | Number of table instances being used. | Name_locked | 1 if the table is name-locked, e.g. if it is being dropped or renamed, otherwise 0. | Before MariaDB 5.5, each use of, for example, LOCK TABLE ... WRITE would increment In_use for that table. With the implementation of the metadata locking improvements in MariaDB 5.5, LOCK TABLE... WRITE acquires a strong MDL lock, and concurrent connections will wait on this MDL lock, so any subsequent LOCK TABLE... WRITE will not increment In_use. Example SHOW OPEN TABLES; +----------+---------------------------+--------+-------------+ | Database | Table | In_use | Name_locked | +----------+---------------------------+--------+-------------+ ... | test | xjson | 0 | 0 | | test | jauthor | 0 | 0 | | test | locks | 1 | 0 | ... +----------+---------------------------+--------+-------------+ URL: https://mariadb.com/kb/en/show-open-tables/https://mariadb.com/kb/en/show-open-tables/3SHOW PACKAGE BODY STATUSOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ SHOW PACKAGE BODY STATUS [LIKE 'pattern' | WHERE expr] Description ----------- The SHOW PACKAGE BODY STATUS statement returns characteristics of stored package bodies (implementations), such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW PACKAGE STATUS, displays information about stored package specifications. The LIKE clause, if present, indicates which package names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information. Examples -------- SHOW PACKAGE BODY STATUS LIKE 'pkg1'\G *************************** 1. row *************************** Db: test Name: pkg1 Type: PACKAGE BODY Definer: root@localhost Modified: 2018-02-27 14:44:14 Created: 2018-02-27 14:44:14 Security_type: DEFINER Comment: This is my first package body character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-package-body-status/https://mariadb.com/kb/en/show-package-body-status/.SHOW PACKAGE STATUSOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ SHOW PACKAGE STATUS [LIKE 'pattern' | WHERE expr] Description ----------- The SHOW PACKAGE STATUS statement returns characteristics of stored package specifications, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW PACKAGE BODY STATUS, displays information about stored package bodies (i.e. implementations). The LIKE clause, if present, indicates which package names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information. Examples -------- SHOW PACKAGE STATUS LIKE 'pkg1'\G *************************** 1. row *************************** Db: test Name: pkg1 Type: PACKAGE Definer: root@localhost Modified: 2018-02-27 14:38:15 Created: 2018-02-27 14:38:15 Security_type: DEFINER Comment: This is my first package character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-package-status/https://mariadb.com/kb/en/show-package-status/  '` T)ĵ- 'SHOW PLUGINSSyntax ------ SHOW PLUGINS; Description ----------- SHOW PLUGINS displays information about installed plugins. The Library column indicates the plugin library - if it is NULL, the plugin is built-in and cannot be uninstalled. The PLUGINS table in the information_schema database contains more detailed information. For specific information about storage engines (a particular type of plugin), see the information_schema.ENGINES table and the SHOW ENGINES statement. Examples -------- SHOW PLUGINS; +----------------------------+----------+--------------------+-------------+---------+ | Name | Status | Type | Library | License | +----------------------------+----------+--------------------+-------------+---------+ | binlog | ACTIVE | STORAGE ENGINE | NULL | GPL | | mysql_native_password | ACTIVE | AUTHENTICATION | NULL | GPL | | mysql_old_password | ACTIVE | AUTHENTICATION | NULL | GPL | | MRG_MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | CSV | ACTIVE | STORAGE ENGINE | NULL | GPL | | MEMORY | ACTIVE | STORAGE ENGINE | NULL | GPL | | FEDERATED | ACTIVE | STORAGE ENGINE | NULL | GPL | | PERFORMANCE_SCHEMA | ACTIVE | STORAGE ENGINE | NULL | GPL | | Aria | ACTIVE | STORAGE ENGINE | NULL | GPL | | InnoDB | ACTIVE | STORAGE ENGINE | NULL | GPL | | INNODB_TRX | ACTIVE | INFORMATION SCHEMA | NULL | GPL | ... | INNODB_SYS_FOREIGN | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_FOREIGN_COLS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | SPHINX | ACTIVE | STORAGE ENGINE | NULL | GPL | | ARCHIVE | ACTIVE | STORAGE ENGINE | NULL | GPL | | BLACKHOLE | ACTIVE | STORAGE ENGINE | NULL | GPL | | FEEDBACK | DISABLED | INFORMATION SCHEMA | NULL | GPL | | partition | ACTIVE | STORAGE ENGINE | NULL | GPL | | pam | ACTIVE | AUTHENTICATION | auth_pam.so | GPL | +----------------------------+----------+--------------------+-------------+---------+ URL: https://mariadb.com/kb/en/show-plugins/https://mariadb.com/kb/en/show-plugins/.SHOW PLUGINS SONAMEMariaDB 10.0.2 SHOW PLUGINS SONAME was introduced in MariaDB 10.0.2 Syntax ------ SHOW PLUGINS SONAME { library | LIKE 'pattern' | WHERE expr }; Description ----------- SHOW PLUGINS SONAME displays information about compiled-in and all server plugins in the plugin_dir directory, including plugins that haven't been installed. Examples -------- SHOW PLUGINS SONAME 'ha_example.so'; +----------+---------------+----------------+---------------+---------+ | Name | Status | Type | Library | License | +----------+---------------+----------------+---------------+---------+ | EXAMPLE | NOT INSTALLED | STORAGE ENGINE | ha_example.so | GPL | | UNUSABLE | NOT INSTALLED | DAEMON | ha_example.so | GPL | +----------+---------------+----------------+---------------+---------+ There is also a corresponding information_schema table, called ALL_PLUGINS, which contains more complete information. URL: https://mariadb.com/kb/en/show-plugins-soname/https://mariadb.com/kb/en/show-plugins-soname/a *SHOW PRIVILEGESSyntax ------ SHOW PRIVILEGES Description ----------- SHOW PRIVILEGES shows the list of system privileges that the MariaDB server supports. The exact list of privileges depends on the version of your server. Note that the Delete history privilege displays as Delete versioning rows (MDEV-20382). Examples -------- SHOW PRIVILEGES; +-------------------------+---------------------------------------+-------------------------------------------------------+ | Privilege | Context | Comment | +-------------------------+---------------------------------------+-------------------------------------------------------+ | Alter | Tables | To alter the table | | Alter routine | Functions,Procedures | To alter or drop stored functions/procedures | | Create | Databases,Tables,Indexes | To create new databases and tables | | Create routine | Databases | To use CREATE FUNCTION/PROCEDURE | | Create temporary tables | Databases | To use CREATE TEMPORARY TABLE | | Create view | Tables | To create new views | | Create user | Server Admin | To create new users | | Delete | Tables | To delete existing rows | | Delete versioning rows | Tables | To delete versioning table historical rows | | Drop | Databases,Tables | To drop databases, tables, and views | | Event | Server Admin | To create, alter, drop and execute events | | Execute | Functions,Procedures | To execute stored routines | | File | File access on server | To read and write files on the server | | Grant option | Databases,Tables,Functions,Procedures | To give to other users those privileges you possess | | Index | Tables | To create or drop indexes | | Insert | Tables | To insert data into tables | | Lock tables | Databases | To use LOCK TABLES (together with SELECT privilege) | | Process | Server Admin | To view the plain text of currently executing queries | | Proxy | Server Admin | To make proxy user possible | | References | Databases,Tables | To have references on tables | | Reload | Server Admin | To reload or refresh tables, logs and privileges | | Replication client | Server Admin | To ask where the slave or master servers are | | Replication slave | Server Admin | To read binary log events from the master | | Select | Tables | To retrieve rows from table | | Show databases | Server Admin | To see all databases with SHOW DATABASES | | Show view | Tables | To see views with SHOW CREATE VIEW | | Shutdown | Server Admin | To shut down the server | | Super | Server Admin | To use KILL thread, SET GLOBAL, CHANGE MASTER, etc. | | Trigger | Tables | To use triggers | | Create tablespace | Server Admin | To create/alter/drop tablespaces | | Update | Tables | To update existing rows | | Usage | Server Admin | No privileges - allow connect only | +-------------------------+---------------------------------------+-------------------------------------------------------+ URL: https://mariadb.com/kb/en/show-privileges/https://mariadb.com/kb/en/show-privileges/   .SHOW PROCEDURE CODESyntax ------ SHOW PROCEDURE CODE proc_name Description ----------- This statement is a MariaDB extension that is available only for servers that have been built with debugging support. It displays a representation of the internal implementation of the named stored procedure. A similar statement, SHOW FUNCTION CODE, displays information about stored functions. Both statements require that you be the owner of the routine or have SELECT access to the mysql.proc table. If the named routine is available, each statement produces a result set. Each row in the result set corresponds to one "instruction" in the routine. The first column is Pos, which is an ordinal number beginning with 0. The second column is Instruction, which contains an SQL statement (usually changed from the original source), or a directive which has meaning only to the stored-routine handler. Examples -------- DELIMITER // CREATE PROCEDURE p1 () BEGIN DECLARE fanta INT DEFAULT 55; DROP TABLE t2; LOOP INSERT INTO t3 VALUES (fanta); END LOOP; END// Query OK, 0 rows affected (0.00 sec) SHOW PROCEDURE CODE p1// +-----+----------------------------------------+ | Pos | Instruction | +-----+----------------------------------------+ | 0 | set fanta@0 55 | | 1 | stmt 9 "DROP TABLE t2" | | 2 | stmt 5 "INSERT INTO t3 VALUES (fanta)" | | 3 | jump 2 | +-----+----------------------------------------+ URL: https://mariadb.com/kb/en/show-procedure-code/https://mariadb.com/kb/en/show-procedure-code/\0SHOW PROCEDURE STATUSSyntax ------ SHOW PROCEDURE STATUS [LIKE 'pattern' | WHERE expr] Description ----------- This statement is a MariaDB extension. It returns characteristics of a stored procedure, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW FUNCTION STATUS, displays information about stored functions. The LIKE clause, if present, indicates which procedure or function names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information. Examples -------- SHOW PROCEDURE STATUS LIKE 'p1'\G *************************** 1. row *************************** Db: test Name: p1 Type: PROCEDURE Definer: root@localhost Modified: 2010-08-23 13:23:03 Created: 2010-08-23 13:23:03 Security_type: DEFINER Comment: character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: latin1_swedish_ci URL: https://mariadb.com/kb/en/show-procedure-status/https://mariadb.com/kb/en/show-procedure-status/q/SHOW RELAYLOG EVENTSSyntax ------ SHOW RELAYLOG ['connection_name'] EVENTS [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count] Description ----------- On replication slaves this command shows the events in the relay log. If 'log_name' is not specified, the first relay log is shown. Syntax for the LIMIT clause is the same as for SELECT ... LIMIT. Using the LIMIT clause is highly recommended because the SHOW RELAYLOG EVENTS command returns the complete contents of the relay log, which can be quite large. This command does not return events related to setting user and system variables. If you need those, use mysqlbinlog. On the replication master, this command does nothing. connection_name connection_name was added as part of multi-source replication added in MariaDB 10.0.1 If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the SHOW RELAYLOG statement will apply to the specified master. connection_name is case-insensitive. URL: https://mariadb.com/kb/en/show-relaylog-events/https://mariadb.com/kb/en/show-relaylog-events/^+SHOW SLAVE HOSTSSyntax ------ SHOW SLAVE HOSTS Description ----------- This command is run on the master and displays a list of replication slaves that are currently registered with it. Only slaves started with the --report-host=host_name option are visible in this list. The list is displayed on any server (not just the master server). The output looks like this: SHOW SLAVE HOSTS; +------------+-----------+------+-----------+ | Server_id | Host | Port | Master_id | +------------+-----------+------+-----------+ | 192168010 | iconnect2 | 3306 | 192168011 | | 1921680101 | athena | 3306 | 192168011 | +------------+-----------+------+-----------+ Server_id: The unique server ID of the slave server, as configured in the server's option file, or on the command line with --server-id=value. Host: The host name of the slave server, as configured in the server's option file, or on the command line with --report-host=host_name. Note that this can differ from the machine name as configured in the operating system. Port: The port the slave server is listening on. Master_id: The unique server ID of the master server that the slave server is replicating from. Some MariaDB and MySQL versions report another variable, rpl_recovery_rank. This variable was never used, and was eventually removed in MariaDB 10.1.2 and MySQL 5.6. URL: https://mariadb.com/kb/en/show-slave-hosts/https://mariadb.com/kb/en/show-slave-hosts/x  T/ +SHOW PROCESSLISTSyntax ------ SHOW [FULL] PROCESSLIST Description ----------- SHOW PROCESSLIST shows you which threads are running. You can also get this information from the information_schema.PROCESSLIST table or the mysqladmin processlist command. If you have the PROCESS privilege, you can see all threads. Otherwise, you can see only your own threads (that is, threads associated with the MariaDB account that you are using). If you do not use the FULL keyword, only the first 100 characters of each statement are shown in the Info field. The columns shown in SHOW PROCESSLIST are: Name | Description | Introduced | ID | The client's process ID. | | USER | The username associated with the process. | | HOST | The host the client is connected to. | | DB | The default database of the process (NULL if no default). | | COMMAND | The command type. See Thread Command Values. | | TIME | The amount of time, in seconds, the process has been in its current state. For a slave SQL thread before MariaDB 10.1, this is the time in seconds between the last replicated event's timestamp and the slave machine's real time. | | STATE | See Thread States. | | INFO | The statement being executed. | | PROGRESS | The total progress of the process (0-100%) (see Progress Reporting). | MariaDB 5.3 | See TIME_MS column in information_schema.PROCESSLIST for differences in the TIME column between MariaDB and MySQL. The information_schema.PROCESSLIST table contains the following additional columns: Name | Description | Introduced | TIME_MS | The amount of time, in milliseconds, the process has been in its current state. | MariaDB 5.1 | STAGE | The stage the process is currently in. | MariaDB 5.3 | MAX_STAGE | The maximum number of stages. | MariaDB 5.3 | PROGRESS | The progress of the process within the current stage (0-100%). | MariaDB 5.3 | MEMORY_USED | The amount of memory used by the process. | MariaDB 10.0.1 | EXAMINED_ROWS | The number of rows the process has examined. | MariaDB 10.0.1 | QUERY_ID | Query ID. | MariaDB 10.0.5 | Note that the PROGRESS field from the information schema, and the PROGRESS field from SHOW PROCESSLIST display different results. SHOW PROCESSLIST shows the total progress, while the information schema shows the progress for the current stage only. Threads can be killed using their thread_id, or, since MariaDB 10.0.5, their query_id, with the KILL statement. Since queries on this table are locking, if the performance_schema is enabled, you may want to query the THREADS table instead. Examples -------- From MariaDB 5.1.x SHOW FULL PROCESSLIST; +---------+-------+-----------+------+---------+------+-------+-----------------------+ | Id | User | Host | db | Command | Time | State | Info | +---------+-------+-----------+------+---------+------+-------+-----------------------+ | 1988880 | dbart | localhost | NULL | Query | 0 | NULL | SHOW FULL PROCESSLIST | +---------+-------+-----------+------+---------+------+-------+-----------------------+ SELECT * FROM information_schema.processlist; +---------+-------+-----------+------+---------+------+-----------+----------------------------------------------+---------+ | ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO | TIME_MS | +---------+-------+-----------+------+---------+------+-----------+----------------------------------------------+---------+ | 1988880 | dbart | localhost | NULL | Query | 0 | executing | SELECT * FROM information_schema.processlist | 0.444 | +---------+-------+-----------+------+---------+------+-----------+----------------------------------------------+---------+ From MariaDB 5.5.x SHOW FULL PROCESSLIST; +-----+------+-----------+------+---------+------+-------+-----------------------+----------+ | Id | User | Host | db | Command | Time | State | Info | Progress | +-----+------+-----------+------+---------+------+-------+-----------------------+----------+ | 126 | root | localhost | NULL | Query | 0 | NULL | SHOW FULL PROCESSLIST | 0.000 | +-----+------+-----------+------+---------+------+-------+-----------------------+----------+ SELECT * FROM information_schema.processlist; +-----+--------+-----------+------+---------+------+-----------+----------------------------------------------+---------+-------+-----------+----------+ | ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO | TIME_MS | STAGE | MAX_STAGE | PROGRESS | +-----+--------+-----------+------+---------+------+-----------+----------------------------------------------+---------+-------+-----------+----------+ | 126 | root | localhost | NULL | Query | 0 | executing | SELECT * FROM information_schema.processlist | 344.718 | 0 | 0 | 0.000 | +-----+--------+-----------+------+---------+------+-----------+----------------------------------------------+---------+-------+-----------+----------+ From MariaDB 10.0.x SHOW PROCESSLIST; +----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+ | Id | User | Host | db | Command | Time | State | Info | Progress | +----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+ | 2 | event_scheduler | localhost | NULL | Daemon | 2693 | Waiting on empty queue | NULL | 0.000 | | 4 | root | localhost | NULL | Query | 0 | Table lock | SHOW PROCESSLIST | 0.000 | +----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+ URL: https://mariadb.com/kb/en/show-processlist/https://mariadb.com/kb/en/show-processlist/ *<`fiq 'SHOW PROFILESyntax ------ SHOW PROFILE [type [, type] ... ] [FOR QUERY n] [LIMIT row_count [OFFSET offset]] type: ALL | BLOCK IO | CONTEXT SWITCHES | CPU | IPC | MEMORY | PAGE FAULTS | SOURCE | SWAPS Description ----------- The SHOW PROFILE and SHOW PROFILES statements display profiling information that indicates resource usage for statements executed during the course of the current session. Profiling is controlled by the profiling session variable, which has a default value of 0 (OFF). Profiling is enabled by setting profiling to 1 or ON: SET profiling = 1; SHOW PROFILES displays a list of the most recent statements sent to the master. The size of the list is controlled by the profiling_history_size session variable, which has a default value of 15. The maximum value is 100. Setting the value to 0 has the practical effect of disabling profiling. All statements are profiled except SHOW PROFILES and SHOW PROFILE, so you will find neither of those statements in the profile list. Malformed statements are profiled. For example, SHOW PROFILING is an illegal statement, and a syntax error occurs if you try to execute it, but it will show up in the profiling list. SHOW PROFILE displays detailed information about a single statement. Without the FOR QUERY n clause, the output pertains to the most recently executed statement. If FOR QUERY n is included, SHOW PROFILE displays information for statement n. The values of n correspond to the Query_ID values displayed by SHOW PROFILES. The LIMIT row_count clause may be given to limit the output to row_count rows. If LIMIT is given, OFFSET offset may be added to begin the output offset rows into the full set of rows. By default, SHOW PROFILE displays Status and Duration columns. The Status values are like the State values displayed by SHOW PROCESSLIST, although there might be some minor differences in interpretation for the two statements for some status values (see http://dev.mysql.com/doc/refman/5.6/en/thread-information.html). Optional type values may be specified to display specific additional types of information: ALL displays all information BLOCK IO displays counts for block input and output operations CONTEXT SWITCHES displays counts for voluntary and involuntary context switches CPU displays user and system CPU usage times IPC displays counts for messages sent and received MEMORY is not currently implemented PAGE FAULTS displays counts for major and minor page faults SOURCE displays the names of functions from the source code, together with the name and line number of the file in which the function occurs SWAPS displays swap counts Profiling is enabled per session. When a session ends, its profiling information is lost. The information_schema.PROFILING table contains similar information. Examples -------- SELECT @@profiling; +-------------+ | @@profiling | +-------------+ | 0 | +-------------+ SET profiling = 1; USE test; DROP TABLE IF EXISTS t1; CREATE TABLE T1 (id INT); SHOW PROFILES; +----------+------------+--------------------------+ | Query_ID | Duration | Query | +----------+------------+--------------------------+ | 1 | 0.00009200 | SELECT DATABASE() | | 2 | 0.00023800 | show databases | | 3 | 0.00018900 | show tables | | 4 | 0.00014700 | DROP TABLE IF EXISTS t1 | | 5 | 0.24476900 | CREATE TABLE T1 (id INT) | +----------+------------+--------------------------+ SHOW PROFILE; +----------------------+----------+ | Status | Duration | +----------------------+----------+ | starting | 0.000042 | | checking permissions | 0.000044 | | creating table | 0.244645 | | After create | 0.000013 | | query end | 0.000003 | | freeing items | 0.000016 | | logging slow query | 0.000003 | | cleaning up | 0.000003 | +----------------------+----------+ SHOW PROFILE FOR QUERY 4; +--------------------+----------+ | Status | Duration | +--------------------+----------+ | starting | 0.000126 | | query end | 0.000004 | | freeing items | 0.000012 | | logging slow query | 0.000003 | | cleaning up | 0.000002 | +--------------------+----------+ SHOW PROFILE CPU FOR QUERY 5; +----------------------+----------+----------+------------+ | Status | Duration | CPU_user | CPU_system | +----------------------+----------+----------+------------+ | starting | 0.000042 | 0.000000 | 0.000000 | | checking permissions | 0.000044 | 0.000000 | 0.000000 | | creating table | 0.244645 | 0.000000 | 0.000000 | | After create | 0.000013 | 0.000000 | 0.000000 | | query end | 0.000003 | 0.000000 | 0.000000 | | freeing items | 0.000016 | 0.000000 | 0.000000 | | logging slow query | 0.000003 | 0.000000 | 0.000000 | | cleaning up | 0.000003 | 0.000000 | 0.000000 | +----------------------+----------+----------+------------+ URL: https://mariadb.com/kb/en/show-profile/https://mariadb.com/kb/en/show-profile/ ,SHOW TABLE STATUSSyntax ------ SHOW TABLE STATUS [{FROM | IN} db_name] [LIKE 'pattern' | WHERE expr] Description ----------- SHOW TABLE STATUS works like SHOW TABLES, but provides more extensive information about each non-TEMPORARY table. The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. The following information is returned: Column | Description | Name | Table name. | Engine | Table storage engine. | Version | Version number from the table's .frm file. | Row_format | Row format (see InnoDB, Aria and MyISAM row formats). | Rows | Number of rows in the table. Some engines, such as XtraDB and InnoDB may store an estimate. | Avg_row_length | Average row length in the table. | Data_length | For InnoDB/XtraDB, the index size, in pages, multiplied by the page size. For Aria and MyISAM, length of the data file, in bytes. For MEMORY, the approximate allocated memory. | Max_data_length | Maximum length of the data file, ie the total number of bytes that could be stored in the table. Not used in XtraDB and InnoDB. | Index_length | Length of the index file. | Data_free | Bytes allocated but unused. For InnoDB tables in a shared tablespace, the free space of the shared tablespace with small safety margin. An estimate in the case of partitioned tables - see the PARTITIONS table. | Auto_increment | Next AUTO_INCREMENT value. | Create_time | Time the table was created. | Update_time | Time the table was last updated. On Windows, the timestamp is not updated on update, so MyISAM values will be inaccurate. In InnoDB, if shared tablespaces are used, will be NULL, while buffering can also delay the update, so the value will differ from the actual time of the last UPDATE, INSERT or DELETE. | Check_time | Time the table was last checked. Not kept by all storage engines, in which case will be NULL. | Collation | Character set and collation. | Checksum | Live checksum value, if any. | Create_options | Extra CREATE TABLE options. | Comment | Table comment provided when MariaDB created the table. | Similar information can be found in the information_schema.TABLES table as well as by using mysqlshow: mysqlshow --status db_name Example show table status\G *************************** 1. row *************************** Name: bus_routes Engine: InnoDB Version: 10 Row_format: Dynamic Rows: 5 Avg_row_length: 3276 Data_length: 16384 Max_data_length: 0 Index_length: 0 Data_free: 0 Auto_increment: NULL Create_time: 2017-05-24 11:17:46 Update_time: NULL Check_time: NULL Collation: latin1_swedish_ci Checksum: NULL Create_options: Comment: URL: https://mariadb.com/kb/en/show-table-status/https://mariadb.com/kb/en/show-table-status/"a 82SSyntax ------ SHOW SLAVE ["connection_name"] STATUS or SHOW ALL SLAVES STATUS Description ----------- This statement is to be run on a slave and provides status information on essential parameters of the replication slave threads. This statement requires the SUPER or the REPLICATION_CLIENT privilege. Multi-source MariaDB 10.0 introduced the FULL and "connection_name" options to allow you to connect to many masters at the same time. ALL SLAVES gives you a list of all connections to the master. The rows will be sorted according to Connection_name. If you specify a connection_name, you only get the information about that connection. If connection_name is not used, then the name set by default_master_connection is used. If the connection name doesn't exist you will get an error: There is no master connection for 'xxx'. Column descriptions Name | Description | Added | Connection_name | Name of the master connection. Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 | Slave_SQL_State | State of SQL thread. Returned with SHOW ALL SLAVES STATUS only. See Slave SQL Thread States. | MariaDB 10.0 | Slave_IO_State | State of I/O thread. See Slave I/O Thread States. | MariaDB 10.0 | Master_host | Master host that the slave is connected to. | | Master_user | Account user name being used to connect to the master. | | Master_port | The port being used to connect to the master. | | Connect_Retry | Time in seconds between retries to connect. The default is 60. The CHANGE MASTER TO statement can set this. The master-retry-count option determines the maximum number of reconnection attempts. | | Master_Log_File | Name of the master binary log file that the I/O thread is currently reading from. | | Read_Master_Log_Pos | Position up to which the I/O thread has read in the current master binary log file. | | Relay_Log_File | Name of the relay log file that the SQL thread is currently processing. | | Relay_Log_Pos | Position up to which the SQL thread has finished processing in the current relay log file. | | Relay_Master_Log_File | Name of the master binary log file that contains the most recent event executed by the SQL thread. | | Slave_IO_Running | Whether the slave I/O thread is running and connected (Yes), running but not connected to a master (Connecting) or not running (No). | | Slave_SQL_Running | Whether or not the SQL thread is running. | | Replicate_Do_DB | Databases specified for replicating with the replicate_do_db option. | | Replicate_Ignore_DB | Databases specified for ignoring with the replicate_ignore_db option. | | Replicate_Do_Table | Tables specified for replicating with the replicate_do_table option. | | Replicate_Ignore_Table | Tables specified for ignoring with the replicate_ignore_table option. | | Replicate_Wild_Do_Table | Tables specified for replicating with the replicate_wild_do_table option. | | Replicate_Wild_Ignore_Table | Tables specified for ignoring with the replicate_wild_ignore_table option. | | Last_Errno | Alias for Last_SQL_Errno (see below) | | Last Error | Alias for Last_SQL_Error (see below) | | Skip_Counter | Number of events that a slave skips from the master, as recorded in the sql_slave_skip_counter system variable. | | Exec_Master_Log_Pos | Position up to which the SQL thread has processed in the current master binary log file. Can be used to start a new slave from a current slave with the CHANGE MASTER TO ... MASTER_LOG_POS option. | | Relay_Log_Space | Total size of all relay log files combined. | | Until_Condition | | | Until_Log_File | The MASTER_LOG_FILE value of the START SLAVE UNTIL condition. | | Until_Log_Pos | The MASTER_LOG_POS value of the START SLAVE UNTIL condition. | | Master_SSL_Allowed | Whether an SSL connection is permitted (Yes), not permitted (No) or permitted but without the slave having SSL support enabled (Ignored) | | Master_SSL_CA_File | The MASTER_SSL_CA option of the CHANGE MASTER TO statement. | | Master_SSL_CA_Path | The MASTER_SSL_CAPATH option of the CHANGE MASTER TO statement. | | Master_SSL_Cert | The MASTER_SSL_CERT option of the CHANGE MASTER TO statement. | | Master_SSL_Cipher | The MASTER_SSL_CIPHER option of the CHANGE MASTER TO statement. | | Master_SSL_Key | The MASTER_SSL_KEY option of the CHANGE MASTER TO statement. | | Seconds_Behind_Master | Difference between the timestamp logged on the master for the event that the slave is currently processing, and the current timestamp on the slave. Zero if the slave is not currently processing an event. From MariaDB 10.0.23 and MariaDB 10.1.9, with parallel replication, seconds_behind_master is updated only after transactions commit. | | Master_SSL_Verify_Server_Cert | The MASTER_SSL_VERIFY_SERVER_CERT option of the CHANGE MASTER TO statement. | | Last_IO_Errno | Error code of the most recent error that caused the I/O thread to stop (also recorded in the slave's error log). 0 means no error. RESET SLAVE or RESET MASTER will reset this value. | | Last_IO_Error | Error message of the most recent error that caused the I/O thread to stop (also recorded in the slave's error log). An empty string means no error. RESET SLAVE or RESET MASTER will reset this value. | | Last_SQL_Errno | Error code of the most recent error that caused the SQL thread to stop (also recorded in the slave's error log). 0 means no error. RESET SLAVE or RESET MASTER will reset this value. | | Last_SQL_Error | Error message of the most recent error that caused the SQL thread to stop (also recorded in the slave's error log). An empty string means no error. RESET SLAVE or RESET MASTER will reset this value. | | Replicate_Ignore_Server_Ids | List of server_ids that are currently being ignored for replication purposes, or an empty string for none, as specified in the IGNORE_SERVER_IDS option of the CHANGE MASTER TO statement. | | Master_Server_Id | The master's server_id value. | | Master_SSL_Crl | The MASTER_SSL_CRL option of the CHANGE MASTER TO statement. | MariaDB 10.0 | Master_SSL_Crlpath | The MASTER_SSL_CRLPATH option of the CHANGE MASTER TO statement. | MariaDB 10.0 | Using_Gtid | Whether or not global transaction ID's are being used for replication (can be No, Slave_Pos, or Current_Pos). | MariaDB 10.0.2 | Gtid_IO_Pos | Current global transaction ID value. | MariaDB 10.0.2 | Retried_transactions | Number of retried transactions for this connection. Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 | Max_relay_log_size | Max relay log size for this connection. Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 | Executed_log_entries | How many log entries the slave has executed. Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 | Slave_received_heartbeats | How many heartbeats we have got from the master. Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 | Slave_heartbeat_period | How often to request a heartbeat packet from the master (in seconds). Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 | Gtid_Slave_Pos | GTID of the last event group replicated on a slave server, for each replication domain, as stored in the gtid_slave_pos system variable. Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 | SQL_Delay | Value specified by MASTER_DELAY in CHANGE MASTER (or 0 if none). | MariaDB 10.2.3 | SQL_Remaining_Delay | When the slave is delaying the execution of an event due to MASTER_DELAY, this is the number of seconds of delay remaining before the event will be applied. Otherwise, the value is NULL. | MariaDB 10.2.3 | Slave_SQL_Running_State | The state of the SQL driver threads, same as in SHOW PROCESSLIST. When the slave is delaying the execution of an event due to MASTER_DELAY, this field displays: "Waiting until MASTER_DELAY seconds after master executed event". | MariaDB 10.2.3 | Slave_DDL_Groups | This status variable counts the occurrence of DDL statements. This is a slave-side counter for optimistic parallel replication. | MariaDB 10.3.7 | Slave_Non_Transћeactional_Groups | This status variable counts the occurrence of non-transactional event groups. This is a slave-side counter for optimistic parallel replication. | MariaDB 10.3.7 | Slave_Transactional_Groups | This status variable counts the occurrence of transactional event groups. This is a slave-side counter for optimistic parallel replication. | MariaDB 10.3.7 | Examples -------- If you issue this statement using the mysql client, you can use a \G statement terminator rather than a semicolon to obtain a more readable vertical layout. SHOW SLAVE STATUS\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: db01.example.com Master_User: replicant Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mariadb-bin.000010 Read_Master_Log_Pos: 548 Relay_Log_File: relay-bin.000004 Relay_Log_Pos: 837 Relay_Master_Log_File: mariadb-bin.000010 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 548 Relay_Log_Space: 1497 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 101 Master_SSL_Crl: Master_SSL_Crlpath: Using_Gtid: No Gtid_IO_Pos: MariaDB [(none)]> SHOW ALL SLAVES STATUS\G *************************** 1. row *************************** Connection_name: Slave_SQL_State: Slave has read all relay log; waiting for the slave I/O thread to update it Slave_IO_State: Waiting for master to send event Master_Host: db01.example.com Master_User: replicant Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mariadb-bin.000010 Read_Master_Log_Pos: 3608 Relay_Log_File: relay-bin.000004 Relay_Log_Pos: 3897 Relay_Master_Log_File: mariadb-bin.000010 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 3608 Relay_Log_Space: 4557 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 101 Master_SSL_Crl: Master_SSL_Crlpath: Using_Gtid: No Gtid_IO_Pos: Retried_transactions: 0 Max_relay_log_size: 104857600 Executed_log_entries: 40 Slave_received_heartbeats: 11 Slave_heartbeat_period: 1800.000 Gtid_Slave_Pos: 0-101-2320 You can also access some of the variables directly from status variables: SET @@default_master_connection="test" ; show status like "%slave%" Variable_name Value Com_show_slave_hosts 0 Com_show_slave_status 0 Com_start_all_slaves 0 Com_start_slave 0 Com_stop_all_slaves 0 Com_stop_slave 0 Rpl_semi_sync_slave_status OFF Slave_connections 0 Slave_heartbeat_period 1800.000 Slave_open_temp_tables 0 Slave_received_heartbeats 0 Slave_retried_transactions 0 Slave_running OFF Slaves_connected 0 Slaves_running 1 URL: https://mariadb.com/kb/en/show-slave-status/https://mariadb.com/kb/en/generated-columns/c, WcCSyntax ------ SHOW [GLOBAL | SESSION] STATUS [LIKE 'pattern' | WHERE expr] Description ----------- SHOW STATUS provides server status information. This information also can be obtained using the mysqladmin extended-status command, or by querying the Information Schema GLOBAL_STATUS and SESSION_STATUS tables. The LIKE clause, if present, indicates which variable names to match. The WHERE clause can be given to select rows using more general conditions. With the GLOBAL modifier, SHOW STATUS displays the status values for all connections to MariaDB. With SESSION, it displays the status values for the current connection. If no modifier is present, the default is SESSION. LOCAL is a synonym for SESSION. If you see a lot of 0 values, the reason is probably that you have used SHOW STATUS with a new connection instead of SHOW GLOBAL STATUS. Some status variables have only a global value. For these, you get the same value for both GLOBAL and SESSION. See Server Status Variables for a full list, scope and description of the variables that can be viewed with SHOW STATUS. The LIKE clause, if present on its own, indicates which variable name to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. Examples -------- Full output from MariaDB 10.1.17: SHOW GLOBAL STATUS; +--------------------------------------------------------------+----------------------------------------+ | Variable_name | Value | +--------------------------------------------------------------+----------------------------------------+ | Aborted_clients | 0 | | Aborted_connects | 0 | | Access_denied_errors | 0 | | Acl_column_grants | 0 | | Acl_database_grants | 2 | | Acl_function_grants | 0 | | Acl_procedure_grants | 0 | | Acl_proxy_users | 2 | | Acl_role_grants | 0 | | Acl_roles | 0 | | Acl_table_grants | 0 | | Acl_users | 6 | | Aria_pagecache_blocks_not_flushed | 0 | | Aria_pagecache_blocks_unused | 15706 | | Aria_pagecache_blocks_used | 0 | | Aria_pagecache_read_requests | 0 | | Aria_pagecache_reads | 0 | | Aria_pagecache_write_requests | 0 | | Aria_pagecache_writes | 0 | | Aria_transaction_log_syncs | 0 | | Binlog_commits | 0 | | Binlog_group_commits | 0 | | Binlog_group_commit_trigger_count | 0 | | Binlog_group_commit_trigger_lock_wait | 0 | | Binlog_group_commit_trigger_timeout | 0 | | Binlog_snapshot_file | | | Binlog_snapshot_position | 0 | | Binlog_bytes_written | 0 | | Binlog_cache_disk_use | 0 | | Binlog_cache_use | 0 | | Binlog_stmt_cache_disk_use | 0 | | Binlog_stmt_cache_use | 0 | | Busy_time | 0.000000 | | Bytes_received | 432 | | Bytes_sent | 15183 | | Com_admin_commands | 1 | | Com_alter_db | 0 | | Com_alter_db_upgrade | 0 | | Com_alter_event | 0 | | Com_alter_function | 0 | | Com_alter_procedure | 0 | | Com_alter_server | 0 | | Com_alter_table | 0 | | Com_alter_tablespace | 0 | | Com_analyze | 0 | | Com_assign_to_keycache | 0 | | Com_begin | 0 | | Com_binlog | 0 | | Com_call_procedure | 0 | | Com_change_db | 0 | | Com_change_master | 0 | | Com_check | 0 | | Com_checksum | 0 | | Com_commit | 0 | | Com_compound_sql | 0 | | Com_create_db | 0 | | Com_create_event | 0 | | Com_create_function | 0 | | Com_create_index | 0 | | Com_create_procedure | 0 | | Com_create_role | 0 | | Com_create_server | 0 | | Com_create_table | 0 | | Com_create_temporary_table | 0 | | Com_create_trigger | 0 | | Com_create_udf | 0 | | Com_create_user | 0 | | Com_create_view | 0 | | Com_dealloc_sql | 0 | | Com_delete | 0 | | Com_delete_multi | 0 | | Com_do | 0 | | Com_drop_db | 0 | | Com_drop_event | 0 | | Com_drop_function | 0 | | Com_drop_index | 0 | | Com_drop_procedure | 0 | | Com_drop_role | 0 | | Com_drop_server | 0 | | Com_drop_table | 0 | | Com_drop_temporary_table | 0 | | Com_drop_trigger | 0 | | Com_drop_user | 0 | | Com_drop_view | 0 | | Com_empty_query | 0 | | Com_execute_sql | 0 | | Com_flush | 0 | | Com_get_diagnostics | 0 | | Com_grant | 0 | | Com_grant_role | 0 | | Com_ha_close | 0 | | Com_ha_open | 0 | | Com_ha_read | 0 | | Com_help | 0 | | Com_insert | 0 | | Com_insert_select | 0 | | Com_install_plugin | 0 | | Com_kill | 0 | | Com_load | 0 | | Com_lock_tables | 0 | | Com_optimize | 0 | | Com_preload_keys | 0 | | Com_prepare_sql | 0 | | Com_purge | 0 | | Com_purge_before_date | 0 | | Com_release_savepoint | 0 | | Com_rename_table | 0 | | Com_rename_user | 0 | | Com_repair | 0 | | Com_replace | 0 | | Com_replace_select | 0 | | Com_reset | 0 | | Com_resignal | 0 | | Com_revoke | 0 | | Com_revoke_all | 0 | | Com_revoke_role | 0 | | Com_rollback | 0 | | Com_rollback_to_savepoint | 0 | | Com_savepoint | 0 | | Com_select | 1 | | Com_set_option | 0 | | Com_show_authors | 0 | | Com_show_binlog_events | 0 | | Com_show_binlogs | 0 | | Com_show_charsets | 0 | | Com_show_collations | 0 | | Com_show_contributors | 0 | | Com_show_create_db | 0 | | Com_show_create_event | 0 | | Com_show_create_func | 0 | | Com_show_create_proc | 0 | | Com_show_create_table | 0 | | Com_show_create_trigger | 0 | | Com_show_databases | 0 | | Com_show_engine_logs | 0 | | Com_show_engine_mutex | 0 | | Com_show_engine_status | 0 | | Com_show_errors | 0 | | Com_show_events | 0 | | Com_show_explain | 0 | | Com_show_fields | 0 | | Com_show_function_status | 0 | | Com_show_generic | 0 | | Com_show_grants | 0 | | Com_show_keys | 0 | | Com_show_master_status | 0 | | Com_show_open_tables | 0 | | Com_show_plugins | 0 | | Com_show_privileges | 0 | | Com_show_procedure_status | 0 | | Com_show_processlist | 0 | | Com_show_profile | 0 | | Com_show_profiles | 0 | | Com_show_relaylog_events | 0 | | Com_show_slave_hosts | 0 | | Com_show_slave_status | 0 | | Com_show_status | 2 | | Com_show_storage_engines | 0 | | Com_show_table_status | 0 | | Com_show_tables | 0 | | Com_show_triggers | 0 | | Com_show_variables | 0 | | Com_show_warnings | 0 | | Com_shutdown | 0 | | Com_signal | 0 | | Com_start_all_slaves | 0 | | Com_start_slave | 0 | | Com_stmt_close | 0 | | Com_stmt_execute | 0 | | Com_stmt_fetch | 0 | | Com_stmt_prepare | 0 | | Com_stmt_reprepare | 0 | | Com_stmt_reset | 0 | | Com_stmt_send_long_data | 0 | | Com_stop_all_slaves | 0 | | Com_stop_slave | 0 | | Com_truncate | 0 | | Com_uninstall_plugin | 0 | | Com_unlock_tables | 0 | | Com_update | 0 | | Com_update_multi | 0 | | Com_xa_commit | 0 | | Com_xa_end | 0 | | Com_xa_prepare | 0 | | Com_xa_recover | 0 | | Com_xa_rollback | 0 | | Com_xa_start | 0 | | Compression | OFF | | Connection_errors_accept | 0 | | Connection_errors_internal | 0 | | Connection_errors_max_connections | 0 | | Connection_errors_peer_address | 0 | | Connection_errors_select | 0 | | Connection_errors_tcpwrap | 0 | | Connections | 4 | | Cpu_time | 0.000000 | | Created_tmp_disk_tables | 0 | | Created_tmp_files | 6 | | Created_tmp_tables | 2 | | Delayed_errors | 0 | | Delayed_insert_threads | 0 | | Delayed_writes | 0 | | Delete_scan | 0 | | Empty_queries | 0 | | Executed_events | 0 | | Executed_triggers | 0 | | Feature_delay_key_write | 0 | | Feature_dynamic_columns | 0 | | Feature_fulltext | 0 | | Feature_gis | 0 | | Feature_locale | 0 | | Feature_subquery | 0 | | Feature_timezone | 0 | | Feature_trigger | 0 | | Feature_xml | 0 | | Flush_commands | 1 | | Handler_commit | 1 | | Handler_delete | 0 | | Handler_discover | 0 | | Handler_external_lock | 0 | | Handler_icp_attempts | 0 | | Handler_icp_match | 0 | | Handler_mrr_init | 0 | | Handler_mrr_key_refills | 0 | | Handler_mrr_rowid_refills | 0 | | Handler_prepare | 0 | | Handler_read_first | 3 | | Handler_read_key | 0 | | Handler_read_last | 0 | | Handler_read_next | 0 | | Handler_read_prev | 0 | | Handler_read_retry | 0 | | Handler_read_rnd | 0 | | Handler_read_rnd_deleted | 0 | | Handler_read_rnd_next | 537 | | Handler_rollback | 0 | | Handler_savepoint | 0 | | Handler_savepoint_rollback | 0 | | Handler_tmp_update | 0 | | Handler_tmp_write | 516 | | Handler_update | 0 | | Handler_write | 0 | | Innodb_available_undo_logs | 128 | | Innodb_background_log_sync | 222 | | Innodb_buffer_pool_bytes_data | 2523136 | | Innodb_buffer_pool_bytes_dirty | 0 | | Innodb_buffer_pool_dump_status | Dumping buffer pool(s) not yet started | | Innodb_buffer_pool_load_status | L+oading buffer pool(s) not yet started | | Innodb_buffer_pool_pages_data | 154 | | Innodb_buffer_pool_pages_dirty | 0 | | Innodb_buffer_pool_pages_flushed | 1 | | Innodb_buffer_pool_pages_free | 8037 | | Innodb_buffer_pool_pages_lru_flushed | 0 | | Innodb_buffer_pool_pages_made_not_young | 0 | | Innodb_buffer_pool_pages_made_young | 0 | | Innodb_buffer_pool_pages_misc | 0 | | Innodb_buffer_pool_pages_old | 0 | | Innodb_buffer_pool_pages_total | 8191 | | Innodb_buffer_pool_read_ahead | 0 | | Innodb_buffer_pool_read_ahead_evicted | 0 | | Innodb_buffer_pool_read_ahead_rnd | 0 | | Innodb_buffer_pool_read_requests | 558 | | Innodb_buffer_pool_reads | 155 | | Innodb_buffer_pool_wait_free | 0 | | Innodb_buffer_pool_write_requests | 1 | | Innodb_checkpoint_age | 0 | | Innodb_checkpoint_max_age | 80826164 | | Innodb_data_fsyncs | 5 | | Innodb_data_pending_fsyncs | 0 | | Innodb_data_pending_reads | 0 | | Innodb_data_pending_writes | 0 | | Innodb_data_read | 2609664 | | Innodb_data_reads | 172 | | Innodb_data_writes | 5 | | Innodb_data_written | 34304 | | Innodb_dblwr_pages_written | 1 | | Innodb_dblwr_writes | 1 | | Innodb_deadlocks | 0 | | Innodb_have_atomic_builtins | ON | | Innodb_history_list_length | 0 | | Innodb_ibuf_discarded_delete_marks | 0 | | Innodb_ibuf_discarded_deletes | 0 | | Innodb_ibuf_discarded_inserts | 0 | | Innodb_ibuf_free_list | 0 | | Innodb_ibuf_merged_delete_marks | 0 | | Innodb_ibuf_merged_deletes | 0 | | Innodb_ibuf_merged_inserts | 0 | | Innodb_ibuf_merges | 0 | | Innodb_ibuf_segment_size | 2 | | Innodb_ibuf_size | 1 | | Innodb_log_waits | 0 | | Innodb_log_write_requests | 0 | | Innodb_log_writes | 1 | | Innodb_lsn_current | 1616829 | | Innodb_lsn_flushed | 1616829 | | Innodb_lsn_last_checkpoint | 1616829 | | Innodb_master_thread_active_loops | 0 | | Innodb_master_thread_idle_loops | 222 | | Innodb_max_trx_id | 2308 | | Innodb_mem_adaptive_hash | 2217568 | | Innodb_mem_dictionary | 630703 | | Innodb_mem_total | 140771328 | | Innodb_mutex_os_waits | 1 | | Innodb_mutex_spin_rounds | 30 | | Innodb_mutex_spin_waits | 1 | | Innodb_oldest_view_low_limit_trx_id | 0 | | Innodb_os_log_fsyncs | 3 | | Innodb_os_log_pending_fsyncs | 0 | | Innodb_os_log_pending_writes | 0 | | Innodb_os_log_written | 512 | | Innodb_page_size | 16384 | | Innodb_pages_created | 0 | | Innodb_pages_read | 154 | | Innodb_pages_written | 1 | | Innodb_purge_trx_id | 0 | | Innodb_purge_undo_no | 0 | | Innodb_read_views_memory | 88 | | Innodb_row_lock_current_waits | 0 | | Innodb_row_lock_time | 0 | | Innodb_row_lock_time_avg | 0 | | Innodb_row_lock_time_max | 0 | | Innodb_row_lock_waits | 0 | | Innodb_rows_deleted | 0 | | Innodb_rows_inserted | 0 | | Innodb_rows_read | 0 | | Innodb_rows_updated | 0 | | Innodb_system_rows_deleted | 0 | | Innodb_system_rows_inserted | 0 | | Innodb_system_rows_read | 0 | | Innodb_system_rows_updated | 0 | | Innodb_s_lock_os_waits | 2 | | Innodb_s_lock_spin_rounds | 60 | | Innodb_s_lock_spin_waits | 2 | | Innodb_truncated_status_writes | 0 | | Innodb_x_lock_os_waits | 0 | | Innodb_x_lock_spin_rounds | 0 | | Innodb_x_lock_spin_waits | 0 | | Innodb_page_compression_saved | 0 | | Innodb_page_compression_trim_sect512 | 0 | | Innodb_page_compression_trim_sect1024 | 0 | | Innodb_page_compression_trim_sect2048 | 0 | | Innodb_page_compression_trim_sect4096 | 0 | | Innodb_page_compression_trim_sect8192 | 0 | | Innodb_page_compression_trim_sect16384 | 0 | | Innodb_page_compression_trim_sect32768 | 0 | | Innodb_num_index_pages_written | 0 | | Innodb_num_non_index_pages_written | 5 | | Innodb_num_pages_page_compressed | 0 | | Innodb_num_page_compressed_trim_op | 0 | | Innodb_num_page_compressed_trim_op_saved | 0 | | Innodb_num_pages_page_decompressed | 0 | | Innodb_num_pages_page_compression_error | 0 | | Innodb_num_pages_encrypted | 0 | | Innodb_num_pages_decrypted | 0 | | Innodb_have_lz4 | OFF | | Innodb_have_lzo | OFF | | Innodb_have_lzma | OFF | | Innodb_have_bzip2 | OFF | | Innodb_have_snappy | OFF | | Innodb_defragment_compression_failures | 0 | | Innodb_defragment_failures | 0 | | Innodb_defragment_count | 0 | | Innodb_onlineddl_rowlog_rows | 0 | | Innodb_onlineddl_rowlog_pct_used | 0 | | Innodb_onlineddl_pct_progress | 0 | | Innodb_secondary_index_triggered_cluster_reads | 0 | | Innodb_secondary_index_triggered_cluster_reads_avoided | 0 | | Innodb_encryption_rotation_pages_read_from_cache | 0 | | Innodb_encryption_rotation_pages_read_from_disk | 0 | | Innodb_encryption_rotation_pages_modified | 0 | | Innodb_encryption_rotation_pages_flushed | 0 | | Innodb_encryption_rotation_estimated_iops | 0 | | Innodb_scrub_background_page_reorganizations | 0 | | Innodb_scrub_background_page_splits | 0 | | Innodb_scrub_background_page_split_failures_underflow | 0 | | Innodb_scrub_background_page_split_failures_out_of_filespace | 0 | | Innodb_scrub_background_page_split_failures_missing_index | 0 | | Innodb_scrub_background_page_split_failures_unknown | 0 | | Key_blocks_not_flushed | 0 | | Key_blocks_unused | 107163 | | Key_blocks_used | 0 | | Key_blocks_warm | 0 | | Key_read_requests | 0 | | Key_reads | 0 | | Key_write_requests | 0 | | Key_writes | 0 | | Last_query_cost | 0.000000 | | Master_gtid_wait_count | 0 | | Master_gtid_wait_time | 0 | | Master_gtid_wait_timeouts | 0 | | Max_statement_time_exceeded | 0 | | Max_used_connections | 1 | | Memory_used | 273614696 | | Not_flushed_delayed_rows | 0 | | Open_files | 25 | | Open_streams | 0 | | Open_table_definitions | 18 | | Open_tables | 11 | | Opened_files | 77 | | Opened_plugin_libraries | 0 | | Opened_table_definitions | 18 | | Opened_tables | 18 | | Opened_views | 0 | | Performance_schema_accounts_lost | 0 | | Performance_schema_cond_classes_lost | 0 | | Performance_schema_cond_instances_lost | 0 | | Performance_schema_digest_lost | 0 | | Performance_schema_file_classes_lost | 0 | | Performance_schema_file_handles_lost | 0 | | Performance_schema_file_instances_lost | 0 | | Performance_schema_hosts_lost | 0 | | Performance_schema_locker_lost | 0 | | Performance_schema_mutex_classes_lost | 0 | | Performance_schema_mutex_instances_lost | 0 | | Performance_schema_rwlock_classes_lost | 0 | | Performance_schema_rwlock_instances_lost | 0 | | Performance_schema_session_connect_attrs_lost | 0 | | Performance_schema_socket_classes_lost | 0 | | Performance_schema_socket_instances_lost | 0 | | Performance_schema_stage_classes_lost | 0 | | Performance_schema_statement_classes_lost | 0 | | Performance_schema_table_handles_lost | 0 | | Performance_schema_table_instances_lost | 0 | | Performance_schema_thread_classes_lost | 0 | | Performance_schema_thread_instances_lost | 0 | | Performance_schema_users_lost | 0 | | Prepared_stmt_count | 0 | | Qcache_free_blocks | 1 | | Qcache_free_memory | 1031336 | | Qcache_hits | 0 | | Qcache_inserts | 0 | | Qcache_lowmem_prunes | 0 | | Qcache_not_cached | 0 | | Qcache_queries_in_cache | 0 | | Qcache_total_blocks | 1 | | Queries | 4 | | Questions | 4 | | Rows_read | 10 | | Rows_sent | 517 | | Rows_tmp_read | 516 | | Rpl_status | AUTH_MASTER | | Select_full_join | 0 | | Select_full_range_join | 0 | | Select_range | 0 | | Select_range_check | 0 | | Select_scan | 2 | | Slave_connections | 0 | | Slave_heartbeat_period | 0.000 | | Slave_open_temp_tables | 0 | | Slave_received_heartbeats | 0 | | Slave_retried_transactions | 0 | | Slave_running | OFF | | Slave_skipped_errors | 0 | | Slaves_connected | 0 | | Slaves_running | 0 | | Slow_launch_threads | 0 | | Slow_queries | 0 | | Sort_merge_passes | 0 | | Sort_priority_queue_sorts | 0 | | Sort_range | 0 | | Sort_rows | 0 | | Sort_scan | 0 | | Ssl_accept_renegotiates | 0 | | Ssl_accepts | 0 | | Ssl_callback_cache_hits | 0 | | Ssl_cipher | | | Ssl_cipher_list | | | Ssl_client_connects | 0 | | Ssl_connect_renegotiates | 0 | | Ssl_ctx_verify_depth | 0 | | Ssl_ctx_verify_mode | 0 | | Ssl_default_timeout | 0 | | Ssl_finished_accepts | 0 | | Ssl_finished_connects | 0 | | Ssl_server_not_after | | | Ssl_server_not_before | | | Ssl_session_cache_hits | 0 | | Ssl_session_cache_misses | 0 | | Ssl_session_cache_mode | NONE | | Ssl_session_cache_overflows | 0 | | Ssl_session_cache_size | 0 | | Ssl_session_cache_timeouts | 0 | | Ssl_seˇ /&SHOW TABLESSyntax ------ SHOW [FULL] TABLES [FROM db_name] [LIKE 'pattern' | WHERE expr] Description ----------- SHOW TABLES lists the non-TEMPORARY tables, sequences and views in a given database. The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. For example, when searching for tables in the test database, the column name for use in the WHERE and LIKE clauses will be Tables_in_test The FULL modifier is supported such that SHOW FULL TABLES displays a second output column. Values for the second column. Table_type, are BASE TABLE for a table, VIEW for a view and SEQUENCE for a sequence. You can also get this information using: mysqlshow db_name See mysqlshow for more details. If you have no privileges for a base table or view, it does not show up in the output from SHOW TABLES or mysqlshow db_name. The information_schema.TABLES table, as well as the SHOW TABLE STATUS statement, provide extended information about tables. Examples -------- SHOW TABLES; +----------------------+ | Tables_in_test | +----------------------+ | animal_count | | animals | | are_the_mooses_loose | | aria_test2 | | t1 | | view1 | +----------------------+ Showing the tables beginning with a only. SHOW TABLES WHERE Tables_in_test LIKE 'a%'; +----------------------+ | Tables_in_test | +----------------------+ | animal_count | | animals | | are_the_mooses_loose | | aria_test2 | +----------------------+ Showing tables and table types: SHOW FULL TABLES; +----------------+------------+ | Tables_in_test | Table_type | +----------------+------------+ | s1 | SEQUENCE | | student | BASE TABLE | | v1 | VIEW | +----------------+------------+ URL: https://mariadb.com/kb/en/show-tables/https://mariadb.com/kb/en/show-tables/v0SHOW TABLE_STATISTICSMariaDB 5.2 introduced the User Statistics feature. Syntax ------ SHOW TABLE_STATISTICS Description ----------- The SHOW TABLE_STATISTICS statement was introduced in MariaDB 5.2 as part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.TABLE_STATISTICS table shows statistics on table usage The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.TABLE_STATISTICS articles for more information. Example From MariaDB 10.0 SHOW TABLE_STATISTICS\G *************************** 1. row *************************** Table_schema: mysql Table_name: proxies_priv Rows_read: 2 Rows_changed: 0 Rows_changed_x_#indexes: 0 *************************** 2. row *************************** Table_schema: test Table_name: employees_example Rows_read: 7 Rows_changed: 0 Rows_changed_x_#indexes: 0 *************************** 3. row *************************** Table_schema: mysql Table_name: user Rows_read: 16 Rows_changed: 0 Rows_changed_x_#indexes: 0 *************************** 4. row *************************** Table_schema: mysql Table_name: db Rows_read: 2 Rows_changed: 0 Rows_changed_x_#indexes: 0 URL: https://mariadb.com/kb/en/show-table-statistics/https://mariadb.com/kb/en/show-table-statistics/ Z (SHOW TRIGGERSSyntax ------ SHOW TRIGGERS [FROM db_name] [LIKE 'pattern' | WHERE expr] Description ----------- SHOW TRIGGERS lists the triggers currently defined for tables in a database (the default database unless a FROM clause is given). This statement requires the TRIGGER privilege (prior to MySQL 5.1.22, it required the SUPER privilege). The LIKE clause, if present on its own, indicates which table names to match and causes the statement to display triggers for those tables. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. Similar information is stored in the information_schema.TRIGGERS table. If there are multiple triggers for the same action, then the triggers are shown in action order. Examples -------- For the trigger defined at Trigger Overview: SHOW triggers Like 'animals' \G *************************** 1. row *************************** Trigger: the_mooses_are_loose Event: INSERT Table: animals Statement: BEGIN IF NEW.name = 'Moose' THEN UPDATE animal_count SET animal_count.animals = animal_count.animals+100; ELSE UPDATE animal_count SET animal_count.animals = animal_count.animals+1; END IF; END Timing: AFTER Created: 2016-09-29 13:53:34.35 sql_mode: Definer: root@localhost character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci Listing all triggers associated with a certain table: SHOW TRIGGERS FROM test WHERE `Table` = 'user' \G *************************** 1. row *************************** Trigger: user_ai Event: INSERT Table: user Statement: BEGIN END Timing: AFTER Created: 2016-09-29 13:53:34.35 sql_mode: Definer: root@% character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci SHOW triggers WHERE Event Like 'Insert' \G *************************** 1. row *************************** Trigger: the_mooses_are_loose Event: INSERT Table: animals Statement: BEGIN IF NEW.name = 'Moose' THEN UPDATE animal_count SET animal_count.animals = animal_count.animals+100; ELSE UPDATE animal_count SET animal_count.animals = animal_count.animals+1; END IF; END Timing: AFTER Created: 2016-09-29 13:53:34.35 sql_mode: Definer: root@localhost character_set_client: utf8 collation_connection: utf8_general_ci Database Collation: latin1_swedish_ci character_set_client is the session value of the character_set_client system variable when the trigger was created. collation_connection is the session value of the collation_connection system variable when the trigger was created. Database Collation is the collation of the database with which the trigger is associated. These columns were added in MariaDB/MySQL 5.1.21. Old triggers created before MySQL 5.7 and MariaDB 10.2.3 has NULL in the Created column. URL: https://mariadb.com/kb/en/show-triggers/https://mariadb.com/kb/en/show-triggers/C z nl/SHOW USER_STATISTICSMariaDB 5.2 introduced the User Statistics feature. Syntax ------ SHOW USER_STATISTICS Description ----------- The SHOW USER_STATISTICS statement was introduced in MariaDB 5.2 as part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.USER_STATISTICS table holds statistics about user activity. You can use this table to find out such things as which user is causing the most load and which users are being abusive. You can also use this table to measure how close to capacity the server may be. The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.USER_STATISTICS table for more information. Example From MariaDB 10.0: SHOW USER_STATISTICS\G *************************** 1. row *************************** User: root Total_connections: 1 Concurrent_connections: 0 Connected_time: 3297 Busy_time: 0.14113400000000006 Cpu_time: 0.017637000000000003 Bytes_received: 969 Bytes_sent: 22355 Binlog_bytes_written: 0 Rows_read: 10 Rows_sent: 67 Rows_deleted: 0 Rows_inserted: 0 Rows_updated: 0 Select_commands: 7 Update_commands: 0 Other_commands: 0 Commit_transactions: 1 Rollback_transactions: 0 Denied_connections: 0 Lost_connections: 0 Access_denied: 0 Empty_queries: 7 URL: https://mariadb.com/kb/en/show-user-statistics/https://mariadb.com/kb/en/show-user-statistics/)SHOW VARIABLESSyntax ------ SHOW [GLOBAL | SESSION] VARIABLES [LIKE 'pattern' | WHERE expr] Description ----------- SHOW VARIABLES shows the values of MariaDB system variables. This information also can be obtained using the mysqladmin variables command. The LIKE clause, if present, indicates which variable names to match. The WHERE clause can be given to select rows using more general conditions. With the GLOBAL modifier, SHOW VARIABLES displays the values that are used for new connections to MariaDB. With SESSION, it displays the values that are in effect for the current connection. If no modifier is present, the default is SESSION. LOCAL is a synonym for SESSION. With a LIKE clause, the statement displays only rows for those variables with names that match the pattern. To obtain the row for a specific variable, use a LIKE clause as shown: SHOW VARIABLES LIKE 'maria_group_commit'; SHOW SESSION VARIABLES LIKE 'maria_group_commit'; To get a list of variables whose name match a pattern, use the "%" wildcard character in a LIKE clause: SHOW VARIABLES LIKE '%maria%'; SHOW GLOBAL VARIABLES LIKE '%maria%'; Wildcard characters can be used in any position within the pattern to be matched. Strictly speaking, because "_" is a wildcard that matches any single character, you should escape it as "\_" to match it literally. In practice, this is rarely necessary. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. See SET for information on setting server system variables. See Server System Variables for a list of all the variables that can be set. You can also see the server variables by querying the Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES tables. Examples -------- SHOW VARIABLES LIKE 'aria%'; +------------------------------------------+---------------------+ | Variable_name | Value | +------------------------------------------+---------------------+ | aria_block_size | 8192 | | aria_checkpoint_interval | 30 | | aria_checkpoint_log_activity | 1048576 | | aria_force_start_after_recovery_failures | 0 | | aria_group_commit | none | | aria_group_commit_interval | 0 | | aria_log_file_size | 1073741824 | | aria_log_purge_type | immediate | | aria_max_sort_file_size | 9223372036853727232 | | aria_page_checksum | ON | | aria_pagecache_age_threshold | 300 | | aria_pagecache_buffer_size | 134217728 | | aria_pagecache_division_limit | 100 | | aria_recover | NORMAL | | aria_repair_threads | 1 | | aria_sort_buffer_size | 134217728 | | aria_stats_method | nulls_unequal | | aria_sync_log_dir | NEWFILE | | aria_used_for_temp_tables | ON | +------------------------------------------+---------------------+ SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE VARIABLE_NAME LIKE 'max_error_count' OR VARIABLE_NAME LIKE 'innodb_sync_spin_loops'; +---------------------------+---------------+--------------+ | VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE | +---------------------------+---------------+--------------+ | MAX_ERROR_COUNT | 64 | 64 | | INNODB_SYNC_SPIN_LOOPS | NULL | 30 | +---------------------------+---------------+--------------+ SET GLOBAL max_error_count=128; SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE VARIABLE_NAME LIKE 'max_error_count' OR VARIABLE_NAME LIKE 'innodb_sync_spin_loops'; +---------------------------+---------------+--------------+ | VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE | +---------------------------+---------------+--------------+ | MAX_ERROR_COUNT | 64 | 128 | | INNODB_SYNC_SPIN_LOOPS | NULL | 30 | +---------------------------+---------------+--------------+ SET GLOBAL max_error_count=128; SHOW VARIABLES LIKE 'max_error_count'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_error_count | 64 | +-----------------+-------+ SHOW GLOBAL VARIABLES LIKE 'max_error_count'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_error_count | 128 | +-----------------+-------+ Because the following variable only has a global scope, the global value is returned even when specifying SESSION (in this case by default): SHOW VARIABLES LIKE 'innodb_sync_spin_loops'; +------------------------+-------+ | Variable_name | Value | +------------------------+-------+ | innodb_sync_spin_loops | 30 | +------------------------+-------+ URL: https://mariadb.com/kb/en/show-variables/https://mariadb.com/kb/en/show-variables/&   (SHOW WARNINGSSyntax ------ SHOW WARNINGS [LIMIT [offset,] row_count] SHOW ERRORS [LIMIT row_count OFFSET offset] SHOW COUNT(*) WARNINGS Description ----------- SHOW WARNINGS shows the error, warning, and note messages that resulted from the last statement that generated messages in the current session. It shows nothing if the last statement used a table and generated no messages. (That is, a statement that uses a table but generates no messages clears the message list.) Statements that do not use tables and do not generate messages have no effect on the message list. A note is different to a warning in that it only appears if the sql_notes variable is set to 1 (the default), and is not converted to an error if strict mode is enabled. A related statement, SHOW ERRORS, shows only the errors. The SHOW COUNT(*) WARNINGS statement displays the total number of errors, warnings, and notes. You can also retrieve this number from the warning_count variable: SHOW COUNT(*) WARNINGS; SELECT @@warning_count; The value of warning_count might be greater than the number of messages displayed by SHOW WARNINGS if the max_error_count system variable is set so low that not all messages are stored. The LIMIT clause has the same syntax as for the SELECT statement. SHOW WARNINGS can be used after EXPLAIN EXTENDED to see how a query is internally rewritten by MariaDB. If the sql_notes server variable is set to 1, Notes are included in the output of SHOW WARNINGS; if it is set to 0, this statement will not show (or count) Notes. The results of SHOW WARNINGS and SHOW COUNT(*) WARNINGS are directly sent to the client. If you need to access those information in a stored program, you can use the GET DIAGNOSTICS statement instead. For a list of MariaDB error codes, see MariaDB Error Codes. The mysql client also has a number of options related to warnings. The \W command will show warnings after every statement, while \w will disable this. Starting the client with the --show-warnings option will show warnings after every statement. MariaDB 10.3.1 implements a stored routine error stack trace. SHOW WARNINGS can also be used to show more information. See the example below. Examples -------- SELECT 1/0; +------+ | 1/0 | +------+ | NULL | +------+ SHOW COUNT(*) WARNINGS; +-------------------------+ | @@session.warning_count | +-------------------------+ | 1 | +-------------------------+ SHOW WARNINGS; +---------+------+---------------+ | Level | Code | Message | +---------+------+---------------+ | Warning | 1365 | Division by 0 | +---------+------+---------------+ Stack Trace From MariaDB 10.3.1, displaying a stack trace: DELIMITER $$ CREATE OR REPLACE PROCEDURE p1() BEGIN DECLARE c CURSOR FOR SELECT * FROM not_existing; OPEN c; CLOSE c; END; $$ CREATE OR REPLACE PROCEDURE p2() BEGIN CALL p1; END; $$ DELIMITER ; CALL p2; ERROR 1146 (42S02): Table 'test.not_existing' doesn't exist SHOW WARNINGS; +-------+------+-----------------------------------------+ | Level | Code | Message | +-------+------+-----------------------------------------+ | Error | 1146 | Table 'test.not_existing' doesn't exist | | Note | 4091 | At line 6 in test.p1 | | Note | 4091 | At line 4 in test.p2 | +-------+------+-----------------------------------------+ SHOW WARNINGS displays a stack trace, showing where the error actually happened: Line 4 in test.p1 is the OPEN command which actually raised the error Line 3 in test.p2 is the CALL statement, calling p1 from p2. URL: https://mariadb.com/kb/en/show-warnings/https://mariadb.com/kb/en/show-warnings/0SHOW WSREP_MEMBERSHIPMariaDB 10.1.2 SHOW WSREP_MEMBERSHIP was introduced with the WSREP_INFO plugin in MariaDB 10.1.2. Syntax ------ SHOW WSREP_MEMBERSHIP Description ----------- The SHOW WSREP_MEMBERSHIP statement returns Galera node cluster membership information. It returns the same information as found in the information_schema.WSREP_MEMBERSHIP table. Only users with the SUPER privilege can access this information. Examples -------- SHOW WSREP_MEMBERSHIP; +-------+--------------------------------------+----------+-----------------+ | Index | Uuid | Name | Address | +-------+--------------------------------------+----------+-----------------+ | 0 | 19058073-8940-11e4-8570-16af7bf8fced | my_node1 | 10.0.2.15:16001 | | 1 | 19f2b0e0-8942-11e4-9cb8-b39e8ee0b5dd | my_node3 | 10.0.2.15:16003 | | 2 | d85e62db-8941-11e4-b1ef-4bc9980e476d | my_node2 | 10.0.2.15:16002 | +-------+--------------------------------------+----------+-----------------+ URL: https://mariadb.com/kb/en/show-wsrep_membership/https://mariadb.com/kb/en/show-wsrep_membership/,SHOW WSREP_STATUSMariaDB 10.1.2 SHOW WSREP_STATUS was introduced with the WSREP_INFO plugin in MariaDB 10.1.2. Syntax ------ SHOW WSREP_STATUS Description ----------- The SHOW WSREP_STATUS statement returns Galera node and cluster status information. It returns the same information as found in the information_schema.WSREP_STATUS table. Only users with the SUPER privilege can access this information. Examples -------- SHOW WSREP_STATUS; +------------+-------------+----------------+--------------+ | Node_Index | Node_Status | Cluster_Status | Cluster_Size | +------------+-------------+----------------+--------------+ | 0 | Synced | Primary | 3 | +------------+-------------+----------------+--------------+ URL: https://mariadb.com/kb/en/show-wsrep_status/https://mariadb.com/kb/en/show-wsrep_status/Q5J )fhvCALLSyntax ------ CALL sp_name([parameter[,...]]) CALL sp_name[()] Description ----------- The CALL statement invokes a stored procedure that was defined previously with CREATE PROCEDURE. Stored procedure names can be specified as database_name.procedure_name. Procedure names and database names can be quoted with backticks (). This is necessary if they are reserved words, or contain special characters. See identifier qualifiers for details. Before MySQL 5.1.13, stored procedures that take no arguments required parentheses. In current releases of MariaDB, CALL p() and CALL p are equivalent. If parentheses are used, any number of spaces, tab characters and new line characters is allowed between the procedure's name and the open parenthesis. CALL can pass back values to its caller using parameters that are declared as OUT or INOUT parameters. If no value is assigned to an OUT parameter, NULL is assigned (and its former value is lost). To pass such values from another stored program you can use user-defined variables, local variables or routine's parameters; in other contexts, you can only use user-defined variables. CALL can also be executed as a prepared statement. Placeholders can be used for IN parameters in all versions of MariaDB; for OUT and INOUT parameters, placeholders can be used since MariaDB 5.5. When the procedure returns, a client program can also obtain the number of rows affected for the final statement executed within the routine: At the SQL level, call the ROW_COUNT() function; from the C API, call the mysql_affected_rows() function. If the CLIENT_MULTI_RESULTS API flag is set, CALL can return any number of resultsets and the called stored procedure can execute prepared statements. If it is not set, at most one resultset can be returned and prepared statements cannot be used within procedures. URL: https://mariadb.com/kb/en/call/https://mariadb.com/kb/en/call/-Concurrent InsertsThe MyISAM storage engine supports concurrent inserts. This feature allows SELECT statements to be executed during INSERT operations, reducing contention. Whether concurrent inserts can be used or not depends on the value of the concurrent_insert server system variable: NEVER (0) disables concurrent inserts. AUTO (1) allows concurrent inserts only when the target table has no free blocks (no data in the middle of the table has been deleted after the last OPTIMIZE TABLE). This is the default. ALWAYS (2) always enables concurrent inserts. If the binary log is used, CREATE TABLE ... SELECT and INSERT ... SELECT statements cannot use concurrent inserts. These statements acquire a read lock on the table, so concurrent inserts will need to wait. This way the log can be safely used to restore data. Concurrent inserts is not used by slaves with the row based replication (see binary log formats). If an INSERT statement contain the HIGH_PRIORITY clause, concurrent inserts cannot be used. INSERT ... DELAYED is usually unneeded if concurrent inserts are enabled. LOAD DATA INFILE uses concurrent inserts if the CONCURRENT keyword is specified and concurrent_insert is not NEVER. This makes the statement slower (even if no other sessions access the table) but reduces contention. LOCK TABLES allows non-conflicting concurrent inserts if a READ LOCAL lock is used. Concurrent inserts are not allowed if the LOCAL keyword is omitted. Notes The decision to enable concurrent insert for a table is done when the table is opened. If you change the value of concurrent_insert it will only affect new opened tables. If you want it to work for also for tables in use or cached, you should do FLUSH TABLES after setting the variable. URL: https://mariadb.com/kb/en/concurrent-inserts/https://mariadb.com/kb/en/concurrent-inserts/L !EXCEPTEXCEPT was introduced in MariaDB 10.3.0. The result of EXCEPT is all records of the left SELECT result set except records which are in right SELECT result set, i.e. it is subtraction of two result sets. Syntax ------ SELECT ... (INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ... [(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...] [ORDER BY [column [, column ...]]] [LIMIT {[offset,] row_count | row_count OFFSET offset}] Please note: ALL is not supported by EXCEPT (and it is difficult to make sense of ALL with EXCEPT). Brackets for explicit operation precedence are not supported; use a subquery in the FROM clause as a workaround). Description ----------- MariaDB has supported EXCEPT and INTERSECT in addition to UNION since MariaDB 10.3. All behavior for naming columns, ORDER BY and LIMIT is the same as for UNION. EXCEPT implicitly supposes a DISTINCT operation. The result of EXCEPT is all records of the left SELECT result except records which are in right SELECT result set, i.e. it is subtraction of two result sets. EXCEPT and UNION have the same operation precedence. Parentheses From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned. Examples -------- Show customers which are not employees: (SELECT e_name AS name, email FROM customers) EXCEPT (SELECT c_name AS name, email FROM employees); Difference between UNION, EXCEPT and INTERSECT: CREATE TABLE seqs (i INT); INSERT INTO seqs VALUES (1),(2),(3),(4),(5),(6); SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 1 | | 2 | | 3 | | 4 | | 5 | | 6 | +------+ SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 1 | | 2 | +------+ SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 3 | +------+ Parentheses for specifying precedence, from MariaDB 10.4.0 CREATE OR REPLACE TABLE t1 (a INT); CREATE OR REPLACE TABLE t2 (b INT); CREATE OR REPLACE TABLE t3 (c INT); INSERT INTO t1 VALUES (1),(2),(3),(4); INSERT INTO t2 VALUES (5),(6); INSERT INTO t3 VALUES (1),(6); ((SELECT a FROM t1) UNION (SELECT b FROM t2)) EXCEPT (SELECT c FROM t3); +------+ | a | +------+ | 2 | | 3 | | 4 | | 5 | +------+ (SELECT a FROM t1) UNION ((SELECT b FROM t2) EXCEPT (SELECT c FROM t3)); +------+ | a | +------+ | 1 | | 2 | | 3 | | 4 | | 5 | +------+ URL: https://mariadb.com/kb/en/except/https://mariadb.com/kb/en/except/ T %jt!DELETESyntax ------ Single-table syntax: DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name [PARTITION (partition_list)] [WHERE where_condition] [ORDER BY ...] [LIMIT row_count] [RETURNING select_expr [, select_expr ...]] Multiple-table syntax: DELETE [LOW_PRIORITY] [QUICK] [IGNORE] tbl_name[.*] [, tbl_name[.*]] ... FROM table_references [WHERE where_condition] Or: DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name[.*] [, tbl_name[.*]] ... USING table_references [WHERE where_condition] Trimming history: DELETE HISTORY FROM tbl_name [PARTITION (partition_list)] [BEFORE SYSTEM_TIME [TIMESTAMP|TRANSACTION] expression] Description ----------- Option | Description | LOW_PRIORITY | Wait until all SELECT's are done before starting the statement. Used with storage engines that uses table locking (MyISAM, Aria etc). See HIGH_PRIORITY and LOW_PRIORITY clauses for details. | QUICK | Signal the storage engine that it should expect that a lot of rows are deleted. The storage engine engine can do things to speed up the DELETE like ignoring merging of data blocks until all rows are deleted from the block (instead of when a block is half full). This speeds up things at the expanse of lost space in data blocks. At least MyISAM and Aria support this feature. | IGNORE | Don't stop the query even if a not-critical error occurs (like data overflow). See How IGNORE works for a full description. | For the single-table syntax, the DELETE statement deletes rows from tbl_name and returns a count of the number of deleted rows. This count can be obtained by calling the ROW_COUNT() function. The WHERE clause, if given, specifies the conditions that identify which rows to delete. With no WHERE clause, all rows are deleted. If the ORDER BY clause is specified, the rows are deleted in the order that is specified. The LIMIT clause places a limit on the number of rows that can be deleted. For the multiple-table syntax, DELETE deletes from each tbl_name the rows that satisfy the conditions. In this case, ORDER BY and LIMIT> cannot be used. A DELETE can also reference tables which are located in different databases; see Identifier Qualifiers for the syntax. where_condition is an expression that evaluates to true for each row to be deleted. It is specified as described in SELECT. Currently, you cannot delete from a table and select from the same table in a subquery. You need the DELETE privilege on a table to delete rows from it. You need only the SELECT privilege for any columns that are only read, such as those named in the WHERE clause. See GRANT. The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details. As stated, a DELETE statement with no WHERE clause deletes all rows. A faster way to do this, when you do not need to know the number of deleted rows, is to use TRUNCATE TABLE. However, within a transaction or if you have a lock on the table, TRUNCATE TABLE cannot be used whereas DELETE can. See TRUNCATE TABLE, and LOCK. From MariaDB 10.0.5, it is possible to return a resultset of the deleted rows for a single table to the client by using the syntax DELETE ... RETURNING select_expr [, select_expr2 ...]] Any of SQL expression that can be calculated from a single row fields is allowed. Subqueries are allowed. The AS keyword is allowed, so it is possible to use aliases. The use of aggregate functions is not allowed. RETURNING cannot be used in multi-table DELETEs. Same Source and Target Table Until MariaDB 10.3.1, deleting from a table with the same source and target was not possible. From MariaDB 10.3.1, this is now possible. For example: DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE b.c2=0); One can use DELETE HISTORY to delete historical information from System-versioned tables. Examples -------- How to use the ORDER BY and LIMIT clauses: DELETE FROM page_hit ORDER BY timestamp LIMIT 1000000; How to use the RETURNING clause: DELETE FROM t RETURNING f1; +------+ | f1 | +------+ | 5 | | 50 | | 500 | +------+ The following statement joins two tables: one is only used to satisfy a WHERE condition, but no row is deleted from it; rows from the other table are deleted, instead. DELETE post FROM blog INNER JOIN post WHERE blog.id = post.blog_id; Deleting from the Same Source and Target CREATE TABLE t1 (c1 INT, c2 INT); DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE b.c2=0); Until MariaDB 10.3.1, this returned: ERROR 1093 (HY000): Table 't1' is specified twice, both as a target for 'DELETE' and as a separate source for From MariaDB 10.3.1: Query OK, 0 rows affected (0.00 sec) URL: https://mariadb.com/kb/en/delete/https://mariadb.com/kb/en/delete/:9HIGH_PRIORITY and LOW_PRIORITYThe XtraDB/InnoDB storage engine uses row-level locking to ensure data integrity. However some storage engines (such as MEMORY, MyISAM, Aria and MERGE) lock the whole table to prevent conflicts. These storage engines use two separate queues to remember pending statements; one is for SELECTs and the other one is for write statements (INSERT, DELETE, UPDATE). By default, the latter has a higher priority. To give write operations a lower priority, the low_priority_updates server system variable can be set to ON. The option is available on both the global and session levels, and it can be set at startup or via the SET statement. When too many table locks have been set by write statements, some pending SELECTs are executed. The maximum number of write locks that can be acquired before this happens is determined by the max_write_lock_count server system variable, which is dynamic. If write statements have a higher priority (default), the priority of individual write statements (INSERT, REPLACE, UPDATE, DELETE) can be changed via the LOW_PRIORITY attribute, and the priority of a SELECT statement can be raised via the HIGH_PRIORITY attribute. Also, LOCK TABLES supports a LOW_PRIORITY attribute for WRITE locks. If read statements have a higher priority, the priority of an INSERT can be changed via the HIGH_PRIORITY attribute. However, the priority of other write statements cannot be raised individually. The use of LOW_PRIORITY or HIGH_PRIORITY for an INSERT prevents Concurrent Inserts from being used. URL: https://mariadb.com/kb/en/high_priority-and-low_priority/https://mariadb.com/kb/en/high_priority-and-low_priority/ b#GROUP BYUse the GROUP BY clause in a SELECT statement to group rows together that have the same value in one or more column, or the same computed value using expressions with any functions and operators except grouping functions. When you use a GROUP BY clause, you will get a single result row for each group of rows that have the same value for the expression given in GROUP BY. When grouping rows, grouping values are compared as if by the = operator. For string values, the = operator ignores trailing whitespace and may normalize characters and ignore case, depending on the collation in use. You can use any of the grouping functions in your select expression. Their values will be calculated based on all the rows that have been grouped together for each result row. If you select a non-grouped column or a value computed from a non-grouped column, it is undefined which row the returned value is taken from. This is not permitted if the ONLY_FULL_GROUP_BY SQL_MODE is used. You can use multiple expressions in the GROUP BY clause, separated by commas. Rows are grouped together if they match on each of the expressions. You can also use a single integer as the grouping expression. If you use an integer n, the results will be grouped by the nth column in the select expression. The WHERE clause is applied before the GROUP BY clause. It filters non-aggregated rows before the rows are grouped together. To filter grouped rows based on aggregate values, use the HAVING clause. The HAVING clause takes any expression and evaluates it as a boolean, just like the WHERE clause. You can use grouping functions in the HAVING clause. As with the select expression, if you reference non-grouped columns in the HAVING clause, the behavior is undefined. By default, if a GROUP BY clause is present, the rows in the output will be sorted by the expressions used in the GROUP BY. You can also specify ASC or DESC (ascending, descending) after those expressions, like in ORDER BY. The default is ASC. If you want the rows to be sorted by another field, you can add an explicit ORDER BY. If you don't want the result to be ordered, you can add ORDER BY NULL. WITH ROLLUP The WITH ROLLUP modifer adds extra rows to the resultset that represent super-aggregate summaries. For a full description with examples, see SELECT WITH ROLLUP. GROUP BY Examples Consider the following table that records how many times each user has played and won a game: CREATE TABLE plays (name VARCHAR(16), plays INT, wins INT); INSERT INTO plays VALUES ("John", 20, 5), ("Robert", 22, 8), ("Wanda", 32, 8), ("Susan", 17, 3); Get a list of win counts along with a count: SELECT wins, COUNT(*) FROM plays GROUP BY wins; +------+----------+ | wins | COUNT(*) | +------+----------+ | 3 | 1 | | 5 | 1 | | 8 | 2 | +------+----------+ 3 rows in set (0.00 sec) The GROUP BY expression can be a computed value, and can refer back to an identifer specified with AS. Get a list of win averages along with a count: SELECT (wins / plays) AS winavg, COUNT(*) FROM plays GROUP BY winavg; +--------+----------+ | winavg | COUNT(*) | +--------+----------+ | 0.1765 | 1 | | 0.2500 | 2 | | 0.3636 | 1 | +--------+----------+ 3 rows in set (0.00 sec) You can use any grouping function in the select expression. For each win average as above, get a list of the average play count taken to get that average: SELECT (wins / plays) AS winavg, AVG(plays) FROM plays GROUP BY winavg; +--------+------------+ | winavg | AVG(plays) | +--------+------------+ | 0.1765 | 17.0000 | | 0.2500 | 26.0000 | | 0.3636 | 22.0000 | +--------+------------+ 3 rows in set (0.00 sec) You can filter on aggregate information using the HAVING clause. The HAVING clause is applied after GROUP BY and allows you to filter on aggregate data that is not available to the WHERE clause. Restrict the above example to results that involve an average number of plays over 20: SELECT (wins / plays) AS winavg, AVG(plays) FROM plays GROUP BY winavg HAVING AVG(plays) > 20; +--------+------------+ | winavg | AVG(plays) | +--------+------------+ | 0.2500 | 26.0000 | | 0.3636 | 22.0000 | +--------+------------+ 2 rows in set (0.00 sec) See Also SELECT Joins and Subqueries LIMIT ORDER BY Common Table Expressions SELECT WITH ROLLUP SELECT INTO OUTFILE SELECT INTO DUMPFILE FOR UPDATE LOCK IN SHARE MODE Optimizer Hints URL: https://mariadb.com/kb/en/group-by/https://mariadb.com/kb/en/group-by/ !IGNOREThe IGNORE option tells the server to ignore some common errors. IGNORE can be used with the following statements: DELETE INSERT (see also INSERT IGNORE) LOAD DATA INFILE UPDATE ALTER TABLE CREATE TABLE ... SELECT INSERT ... SELECT The logic used: Variables out of ranges are replaced with the maximum/minimum value. SQL_MODEs STRICT_TRANS_TABLES, STRICT_ALL_TABLES, NO_ZERO_IN_DATE, NO_ZERO_DATE are ignored. Inserting NULL in a NOT NULL field will insert 0 ( in a numerical field), 0000-00-00 ( in a date field) or an empty string ( in a character field). Rows that cause a duplicate key error or break a foreign key constraint are not inserted, updated, or deleted. The following errors are ignored: Error number | Symbolic error name | Description | 1022 | ER_DUP_KEY | Can't write; duplicate key in table '%s' | 1048 | ER_BAD_NULL_ERROR | Column '%s' cannot be null | 1062 | ER_DUP_ENTRY | Duplicate entry '%s' for key %d | 1242 | ER_SUBQUERY_NO_1_ROW | Subquery returns more than 1 row | 1264 | ER_WARN_DATA_OUT_OF_RANGE | Out of range value for column '%s' at row %ld | 1265 | WARN_DATA_TRUNCATED | Data truncated for column '%s' at row %ld | 1292 | ER_TRUNCATED_WRONG_VALUE | Truncated incorrect %s value: '%s' | 1366 | ER_TRUNCATED_WRONG_VALUE_FOR_FIELD | Incorrect integer value | 1369 | ER_VIEW_CHECK_FAILED | CHECK OPTION failed '%s.%s' | 1451 | ER_ROW_IS_REFERENCED_2 | Cannot delete or update a parent row | 1452 | ER_NO_REFERENCED_ROW_2 | Cannot add or update a child row: a foreign key constraint fails (%s) | 1526 | ER_NO_PARTITION_FOR_GIVEN_VALUE | Table has no partition for value %s | 1586 | ER_DUP_ENTRY_WITH_KEY_NAME | Duplicate entry '%s' for key '%s' | 1591 | ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENT | Table has no partition for some existing values | 1748 | ER_ROW_DOES_NOT_MATCH_GIVEN_PARTITION_SET | Found a row not matching the given partition set | Ignored errors normally generate a warning. A property of the IGNORE clause consists in causing transactional engines and non-transactional engines (like XtraDB and Aria) to behave the same way. For example, normally a multi-row insert which tries to violate a UNIQUE contraint is completely rolled back on XtraDB/InnoDB, but might be partially executed on Aria. With the IGNORE clause, the statement will be partially executed in both engines. Starting from MariaDB 5.5.28 duplicate key errors also generate warnings. The OLD_MODE server variable can be used to prevent this. URL: https://mariadb.com/kb/en/ignore/https://mariadb.com/kb/en/ignore/H ` !INSERTSyntax ------ INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE] [INTO] tbl_name [PARTITION (partition_list)] [(col,...)] {VALUES | VALUE} ({expr | DEFAULT},...),(...),... [ ON DUPLICATE KEY UPDATE col=expr [, col=expr] ... ] Or: INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE] [INTO] tbl_name [PARTITION (partition_list)] SET col={expr | DEFAULT}, ... [ ON DUPLICATE KEY UPDATE col=expr [, col=expr] ... ] Or: INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE] [INTO] tbl_name [PARTITION (partition_list)] [(col,...)] SELECT ... [ ON DUPLICATE KEY UPDATE col=expr [, col=expr] ... ] The INSERT statement is used to insert new rows into an existing table. The INSERT ... VALUES and INSERT ... SET forms of the statement insert rows based on explicitly specified values. The INSERT ... SELECT form inserts rows selected from another table or tables. INSERT ... SELECT is discussed further in the INSERT ... SELECT article. The table name can be specified in the form db_name.tbl_name or, if a default database is selected, in the form tbl_name (see Identifier Qualifiers). This allows to use INSERT ... SELECT to copy rows between different databases. The PARTITION clause was introduced in MariaDB 10.0. It can be used in both the INSERT and the SELECT part. See Partition Pruning and Selection for details. The columns list is optional. It specifies which values are explicitly inserted, and in which order. If this clause is not specified, all values must be explicitly specified, in the same order they are listed in the table definition. The list of value follow the VALUES or VALUE keyword (which are interchangeable, regardless how much values you want to insert), and is wrapped by parenthesis. The values must be listed in the same order as the columns list. It is possible to specify more than one list to insert more than one rows with a single statement. If many rows are inserted, this is a speed optimization. For one-row statements, the SET clause may be more simple, because you don't need to remember the columns order. All values are specified in the form col = expr. Values can also be specified in the form of a SQL expression or subquery. However, the subquery cannot access the same table that is named in the INTO clause. If you use the LOW_PRIORITY keyword, execution of the INSERT is delayed until no other clients are reading from the table. If you use the HIGH_PRIORITY keyword, the statement has the same priority as SELECTs. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). However, if one of these keywords is specified, concurrent inserts cannot be used. See HIGH_PRIORITY and LOW_PRIORITY clauses for details. INSERT DELAYED For more details on the DELAYED option, see INSERT DELAYED. HIGH PRIORITY and LOW PRIORITY See HIGH_PRIORITY and LOW_PRIORITY. Defaults and Duplicate Values See INSERT - Default & Duplicate Values for details.. INSERT IGNORE See INSERT IGNORE. INSERT ON DUPLICATE KEY UPDATE See INSERT ON DUPLICATE KEY UPDATE. Examples -------- Specifying the column names: INSERT INTO person (first_name, last_name) VALUES ('John', 'Doe'); Inserting more than 1 row at a time: INSERT INTO tbl_name VALUES (1, "row 1"), (2, "row 2"); Using the SET clause: INSERT INTO person SET first_name = 'John', last_name = 'Doe'; SELECTing from another table: INSERT INTO contractor SELECT * FROM person WHERE status = 'c'; See INSERT ON DUPLICATE KEY UPDATE and INSERT IGNORE for further examples. URL: https://mariadb.com/kb/en/insert/https://mariadb.com/kb/en/insert/'<:INSERT - Default & Duplicate ValuesDefault Values If the SQL_MODE contains STRICT_TRANS_TABLES and you are inserting into a transactional table (like InnoDB), or if the SQL_MODE contains STRICT_ALL_TABLES, all NOT NULL columns which does not have a DEFAULT value (and is not AUTO_INCREMENT) must be explicitly referenced in INSERT statements. If not, an error like this is produced: ERROR 1364 (HY000): Field 'col' doesn't have a default value In all other cases, if a NOT NULL column without a DEFAULT value is not referenced, an empty value will be inserted (for example, 0 for INTEGER columns and '' for CHAR columns). See NULL Values in MariaDB:Inserting for examples. If a NOT NULL column having a DEFAULT value is not referenced, NULL will be inserted. If a NULL column having a DEFAULT value is not referenced, its default value will be inserted. It is also possible to explicitly assign the default value using the DEFAULT keyword or the DEFAULT() function. If the DEFAULT keyword is used but the column does not have a DEFAULT value, an error like this is produced: ERROR 1364 (HY000): Field 'col' doesn't have a default value Duplicate Values By default, if you try to insert a duplicate row and there is a UNIQUE index, INSERT stops and an error like this is produced: ERROR 1062 (23000): Duplicate entry 'dup_value' for key 'col' To handle duplicates you can use the IGNORE clause, INSERT ON DUPLICATE KEY UPDATE or the REPLACE statement. Note that the IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE. URL: https://mariadb.com/kb/en/insert-default-duplicate-values/https://mariadb.com/kb/en/insert-default-duplicate-values/U I r  )INSERT DELAYEDSyntax ------ INSERT DELAYED ... Description ----------- The DELAYED option for the INSERT statement is a MariaDB/MySQL extension to standard SQL that is very useful if you have clients that cannot or need not wait for the INSERT to complete. This is a common situation when you use MariaDB for logging and you also periodically run SELECT and UPDATE statements that take a long time to complete. When a client uses INSERT DELAYED, it gets an okay from the server at once, and the row is queued to be inserted when the table is not in use by any other thread. Another major benefit of using INSERT DELAYED is that inserts from many clients are bundled together and written in one block. This is much faster than performing many separate inserts. Note that INSERT DELAYED is slower than a normal INSERT if the table is not otherwise in use. There is also the additional overhead for the server to handle a separate thread for each table for which there are delayed rows. This means that you should use INSERT DELAYED only when you are really sure that you need it. The queued rows are held only in memory until they are inserted into the table. This means that if you terminate mysqld forcibly (for example, with kill -9) or if mysqld dies unexpectedly, any queued rows that have not been written to disk are lost. The number of concurrent INSERT DELAYED threads is limited by the max_delayed_threads server system variables. If it is set to 0, INSERT DELAYED is disabled. The session value can be equal to the global value, or 0 to disable this statement for the current session. If this limit has been reached, the DELAYED clause will be silently ignore for subsequent statements (no error will be produced). There are some constraints on the use of DELAYED: INSERT DELAYED works only with MyISAM, MEMORY, ARCHIVE, and BLACKHOLE tables. If you execute INSERT DELAYED with another storage engine, you will get an error like this: ERROR 1616 (HY000): DELAYED option not supported for table 'tab_name' For MyISAM tables, if there are no free blocks in the middle of the data file, concurrent SELECT and INSERT statements are supported. Under these circumstances, you very seldom need to use INSERT DELAYED with MyISAM. INSERT DELAYED should be used only for INSERT statements that specify value lists. The server ignores DELAYED for INSERT ... SELECT or INSERT ... ON DUPLICATE KEY UPDATE statements. Because the INSERT DELAYED statement returns immediately, before the rows are inserted, you cannot use LAST_INSERT_ID() to get the AUTO_INCREMENT value that the statement might generate. DELAYED rows are not visible to SELECT statements until they actually have been inserted. After INSERT DELAYED, ROW_COUNT() returns the number of the rows you tried to insert, not the number of the successful writes. DELAYED is ignored on slave replication servers, so that INSERT DELAYED is treated as a normal INSERT on slaves. This is because DELAYED could cause the slave to have different data than the master. INSERT DELAYED statements are not safe for replication. Pending INSERT DELAYED statements are lost if a table is write locked and ALTER TABLE is used to modify the table structure. INSERT DELAYED is not supported for views. If you try, you will get an error like this: ERROR 1347 (HY000): 'view_name' is not BASE TABLE INSERT DELAYED is not supported for partitioned tables. INSERT DELAYED is not supported within stored programs. URL: https://mariadb.com/kb/en/insert-delayed/https://mariadb.com/kb/en/insert-delayed/ (INSERT IGNOREIgnoring Errors Normally INSERT stops and rolls back when it encounters an error. By using the IGNORE keyword all errors are converted to warnings, which will not stop inserts of additional rows. The IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE. Incompatibilities MariaDB until 5.5.28 MySQL and MariaDB before 5.5.28 didn't give warnings for duplicate key errors when using IGNORE. You can get the old behaviour if you set OLD_MODE to NO_DUP_KEY_WARNINGS_WITH_IGNORE Examples -------- CREATE TABLE t1 (x INT UNIQUE); INSERT INTO t1 VALUES(1),(2); INSERT INTO t1 VALUES(2),(3); ERROR 1062 (23000): Duplicate entry '2' for key 'x' SELECT * FROM t1; +------+ | x | +------+ | 1 | | 2 | +------+ 2 rows in set (0.00 sec) INSERT IGNORE INTO t1 VALUES(2),(3); Query OK, 1 row affected, 1 warning (0.04 sec) SHOW WARNINGS; +---------+------+---------------------------------+ | Level | Code | Message | +---------+------+---------------------------------+ | Warning | 1062 | Duplicate entry '2' for key 'x' | +---------+------+---------------------------------+ SELECT * FROM t1; +------+ | x | +------+ | 1 | | 2 | | 3 | +------+ See INSERT ON DUPLICATE KEY UPDATE for further examples using that syntax. URL: https://mariadb.com/kb/en/insert-ignore/https://mariadb.com/kb/en/insert-ignore/a Nօ9INSERT ON DUPLICATE KEY UPDATESyntax ------ INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE] [INTO] tbl_name [PARTITION (partition_list)] [(col,...)] {VALUES | VALUE} ({expr | DEFAULT},...),(...),... [ ON DUPLICATE KEY UPDATE col=expr [, col=expr] ... ] Or: INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE] [INTO] tbl_name [PARTITION (partition_list)] SET col={expr | DEFAULT}, ... [ ON DUPLICATE KEY UPDATE col=expr [, col=expr] ... ] Or: INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE] [INTO] tbl_name [PARTITION (partition_list)] [(col,...)] SELECT ... [ ON DUPLICATE KEY UPDATE col=expr [, col=expr] ... ] Description ----------- INSERT ... ON DUPLICATE KEY UPDATE is a MariaDB/MySQL extension to the INSERT statement that, if it finds a duplicate unique or primary key, will instead perform an UPDATE. The row/s affected value is reported as 1 if a row is inserted, and 2 if a row is updated, unless the API's CLIENT_FOUND_ROWS flag is set. If more than one unique index is matched, only the first is updated. It is not recommended to use this statement on tables with more than one unique index. If the table has an AUTO_INCREMENT primary key and the statement inserts or updates a row, the LAST_INSERT_ID() function returns its AUTO_INCREMENT value. The VALUES() function can only be used in a ON DUPLICATE KEY UPDATE clause and has no meaning in any other context. It returns the column values from the INSERT portion of the statement. This function is particularly useful for multi-rows inserts. The IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE. The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details. This statement activates INSERT and UPDATE triggers. See Trigger Overview for details. See also a similar statement, REPLACE. Examples -------- CREATE TABLE ins_duplicate (id INT PRIMARY KEY, animal VARCHAR(30)); INSERT INTO ins_duplicate VALUES (1,'Aardvark'), (2,'Cheetah'), (3,'Zebra'); If there is no existing key, the statement runs as a regular INSERT: INSERT INTO ins_duplicate VALUES (4,'Gorilla') ON DUPLICATE KEY UPDATE animal='Gorilla'; Query OK, 1 row affected (0.07 sec) SELECT * FROM ins_duplicate; +----+----------+ | id | animal | +----+----------+ | 1 | Aardvark | | 2 | Cheetah | | 3 | Zebra | | 4 | Gorilla | +----+----------+ A regular INSERT with a primary key value of 1 will fail, due to the existing key: INSERT INTO ins_duplicate VALUES (1,'Antelope'); ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY' However, we can use an INSERT ON DUPLICATE KEY UPDATE instead: INSERT INTO ins_duplicate VALUES (1,'Antelope') ON DUPLICATE KEY UPDATE animal='Antelope'; Query OK, 2 rows affected (0.09 sec) Note that there are two rows reported as affected, but this refers only to the UPDATE. SELECT * FROM ins_duplicate; +----+----------+ | id | animal | +----+----------+ | 1 | Antelope | | 2 | Cheetah | | 3 | Zebra | | 4 | Gorilla | +----+----------+ Adding a second unique column: ALTER TABLE ins_duplicate ADD id2 INT; UPDATE ins_duplicate SET id2=id+10; ALTER TABLE ins_duplicate ADD UNIQUE KEY(id2); Where two rows match the unique keys match, only the first is updated. This can be unsafe and is not recommended unless you are certain what you are doing. Note that the warning shown below appears in MariaDB 5.5 and before, but has been removed in MariaDB 10.0, as MariaDB now assumes that the keys are checked in order, as shown in SHOW CREATE TABLE. INSERT INTO ins_duplicate VALUES (2,'Lion',13) ON DUPLICATE KEY UPDATE animal='Lion'; Query OK, 2 rows affected, 1 warning (0.06 sec) SHOW WARNINGS; +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Note | 1592 | Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. INSERT... ON DUPLICATE KEY UPDATE on a table with more than one UNIQUE KEY is unsafe | +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ SELECT * FROM ins_duplicate; +----+----------+------+ | id | animal | id2 | +----+----------+------+ | 1 | Antelope | 11 | | 2 | Lion | 12 | | 3 | Zebra | 13 | | 4 | Gorilla | 14 | +----+----------+------+ Although the third row with an id of 3 has an id2 of 13, which also matched, it was not updated. Changing id to an auto_increment field. If a new row is added, the auto_increment is moved forward. If the row is updated, it remains the same. ALTER TABLE `ins_duplicate` CHANGE `id` `id` INT( 11 ) NOT NULL AUTO_INCREMENT; ALTER TABLE ins_duplicate DROP id2; SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate'; +----------------+ | Auto_increment | +----------------+ | 5 | +----------------+ INSERT INTO ins_duplicate VALUES (2,'Leopard') ON DUPLICATE KEY UPDATE animal='Leopard'; Query OK, 2 rows affected (0.00 sec) SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate'; +----------------+ | Auto_increment | +----------------+ | 5 | +----------------+ INSERT INTO ins_duplicate VALUES (5,'Wild Dog') ON DUPLICATE KEY UPDATE animal='Wild Dog'; Query OK, 1 row affected (0.09 sec) SELECT * FROM ins_duplicate; +----+----------+ | id | animal | +----+----------+ | 1 | Antelope | | 2 | Leopard | | 3 | Zebra | | 4 | Gorilla | | 5 | Wild Dog | +----+----------+ SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate'; +----------------+ | Auto_increment | +----------------+ | 6 | +----------------+ Refering to column values from the INSERT portion of the statement: INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6) ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b); See the VALUES() function for more. URL: https://mariadb.com/kb/en/insert-on-duplicate-key-update/https://mariadb.com/kb/en/insert-on-duplicate-key-update/  B M(INSERT SELECTSyntax ------ INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE] [INTO] tbl_name [(col_name,...)] SELECT ... [ ON DUPLICATE KEY UPDATE col_name=expr, ... ] Description ----------- With INSERT ... SELECT, you can quickly insert many rows into a table from one or more other tables. For example: INSERT INTO tbl_temp2 (fld_id) SELECT tbl_temp1.fld_order_id FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100; tbl_name can also be specified in the form db_name.tbl_name (see Identifier Qualifiers). This allows to copy rows between different databases. If the new table has a primary key or UNIQUE indexes, you can use IGNORE to handle duplicate key errors during the query. The newer values will not be inserted if an identical value already exists. REPLACE can be used instead of INSERT to prevent duplicates on UNIQUE indexes by deleting old values. In that case, ON DUPLICATE KEY UPDATE cannot be used. INSERT ... SELECT works for tables which already exist. To create a table for a given resultset, you can use CREATE TABLE ... SELECT. URL: https://mariadb.com/kb/en/insert-select/https://mariadb.com/kb/en/insert-select/  $INTERSECTINTERSECT was introduced in MariaDB 10.3.0. The result of an intersect is the intersection of right and left SELECT results, i.e. only records that are present in both result sets will be included in the result of the operation. Syntax ------ SELECT ... (INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ... [(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...] [ORDER BY [column [, column ...]]] [LIMIT {[offset,] row_count | row_count OFFSET offset}] Please note: ALL is not supported by INTERSECT (and it is difficult to make sense of ALL with INTERSECT). Brackets for explicit operation precedence are not supported; use a subquery in the FROM clause as a workaround). Description ----------- MariaDB has supported INTERSECT (as well as EXCEPT) in addition to UNION since MariaDB 10.3. All behavior for naming columns, ORDER BY and LIMIT is the same as for UNION. INTERSECT implicitly supposes a DISTINCT operation. The result of an intersect is the intersection of right and left SELECT results, i.e. only records that are present in both result sets will be included in the result of the operation. INTERSECT has higher precedence than UNION and EXCEPT. If possible it will be executed linearly but if not it will be translated to a subquery in the FROM clause: (select a,b from t1) union (select c,d from t2) intersect (select e,f from t3) union (select 4,4); will be translated to: (select a,b from t1) union select c,d from ((select c,d from t2) intersect (select e,f from t3)) dummy_subselect union (select 4,4) Parentheses From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned. Examples -------- Show customers which are employees: (SELECT e_name AS name, email FROM employees) INTERSECT (SELECT c_name AS name, email FROM customers); Difference between UNION, EXCEPT and INTERSECT: CREATE TABLE seqs (i INT); INSERT INTO seqs VALUES (1),(2),(3),(4),(5),(6); SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 1 | | 2 | | 3 | | 4 | | 5 | | 6 | +------+ SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 1 | | 2 | +------+ SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 3 | +------+ Parentheses for specifying precedence, from MariaDB 10.4.0 CREATE OR REPLACE TABLE t1 (a INT); CREATE OR REPLACE TABLE t2 (b INT); CREATE OR REPLACE TABLE t3 (c INT); INSERT INTO t1 VALUES (1),(2),(3),(4); INSERT INTO t2 VALUES (5),(6); INSERT INTO t3 VALUES (1),(6); ((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT (SELECT c FROM t3); +------+ | a | +------+ | 1 | | 6 | +------+ (SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT (SELECT c FROM t3)); +------+ | a | +------+ | 1 | | 2 | | 3 | | 4 | | 6 | +------+ URL: https://mariadb.com/kb/en/intersect/https://mariadb.com/kb/en/intersect/ M &JOIN SyntaxDescription ----------- MariaDB supports the following JOIN syntaxes for the table_references part of SELECT statements and multiple-table DELETE and UPDATE statements: table_references: table_reference [, table_reference] ... table_reference: table_factor | join_table table_factor: tbl_name [PARTITION (partition_list)] [query_system_time_period_specification] [[AS] alias] [index_hint_list] | table_subquery [query_system_time_period_specification] [AS] alias | ( table_references ) | { ON table_reference LEFT OUTER JOIN table_reference ON conditional_expr } join_table: table_reference [INNER | CROSS] JOIN table_factor [join_condition] | table_reference STRAIGHT_JOIN table_factor | table_reference STRAIGHT_JOIN table_factor ON conditional_expr | table_reference {LEFT|RIGHT} [OUTER] JOIN table_reference join_condition | table_reference NATURAL [{LEFT|RIGHT} [OUTER]] JOIN table_factor join_condition: ON conditional_expr | USING (column_list) query_system_time_period_specification: FOR SYSTEM_TIME AS OF point_in_time | FOR SYSTEM_TIME BETWEEN point_in_time AND point_in_time | FOR SYSTEM_TIME FROM point_in_time TO point_in_time | FOR SYSTEM_TIME ALL point_in_time: [TIMESTAMP] expression | TRANSACTION expression index_hint_list: index_hint [, index_hint] ... index_hint: USE {INDEX|KEY} [{FOR {JOIN|ORDER BY|GROUP BY}] ([index_list]) | IGNORE {INDEX|KEY} [{FOR {JOIN|ORDER BY|GROUP BY}] (index_list) | FORCE {INDEX|KEY} [{FOR {JOIN|ORDER BY|GROUP BY}] (index_list) index_list: index_name [, index_name] ... A table reference is also known as a join expression. Each table can also be specified as db_name.tabl_name. This allows to write queries which involve multiple databases. See Identifier Qualifiers for syntax details. The syntax of table_factor is extended in comparison with the SQL Standard. The latter accepts only table_reference, not a list of them inside a pair of parentheses. This is a conservative extension if we consider each comma in a list of table_reference items as equivalent to an inner join. For example: SELECT * FROM t1 LEFT JOIN (t2, t3, t4) ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c) is equivalent to: SELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4) ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c) In MariaDB, CROSS JOIN is a syntactic equivalent to INNER JOIN (they can replace each other). In standard SQL, they are not equivalent. INNER JOIN is used with an ON clause, CROSS JOIN is used otherwise. In general, parentheses can be ignored in join expressions containing only inner join operations. MariaDB also supports nested joins (see http://dev.mysql.com/doc/refman/5.1/en/nested-join-optimization.html). See System-versioned tables for more information about FOR SYSTEM_TIME syntax. Index hints can be specified to affect how the MariaDB optimizer makes use of indexes. For more information, see How to force query plans. Examples -------- SELECT left_tbl.* FROM left_tbl LEFT JOIN right_tbl ON left_tbl.id = right_tbl.id WHERE right_tbl.id IS NULL; URL: https://mariadb.com/kb/en/join-syntax/https://mariadb.com/kb/en/join-syntax/ A 2 LIMITDescription ----------- Use the LIMIT clause to restrict the number of returned rows. When you use a single integer n with LIMIT, the first n rows will be returned. Use the ORDER BY clause to control which rows come first. You can also select a number of rows after an offset using either of the following: LIMIT offset, row_count LIMIT row_count OFFSET offset When you provide an offset m with a limit n, the first m rows will be ignored, and the following n rows will be returned. Executing an UPDATE with the LIMIT clause is not safe for replication. Since MariaDB 10.0.11, LIMIT 0 has been an exception to this rule (see MDEV-6170). Beginning in MariaDB 5.5.21, there is a LIMIT ROWS EXAMINED optimization which provides the means to terminate the execution of SELECT statements which examine too many rows, and thus use too many resources. See LIMIT ROWS EXAMINED. Multi-Table Updates Until MariaDB 10.3.1, it was not possible to use LIMIT (or ORDER BY) in a multi-table UPDATE statement. This restriction was lifted in MariaDB 10.3.2. GROUP_CONCAT Starting from MariaDB 10.3.3, it is possible to use LIMIT with GROUP_CONCAT(). Examples -------- CREATE TABLE members (name VARCHAR(20)); INSERT INTO members VALUES('Jagdish'),('Kenny'),('Rokurou'),('Immaculada'); SELECT * FROM members; +------------+ | name | +------------+ | Jagdish | | Kenny | | Rokurou | | Immaculada | +------------+ Select the first two names (no ordering specified): SELECT * FROM members LIMIT 2; +---------+ | name | +---------+ | Jagdish | | Kenny | +---------+ All the names in alphabetical order: SELECT * FROM members ORDER BY name; +------------+ | name | +------------+ | Immaculada | | Jagdish | | Kenny | | Rokurou | +------------+ The first two names, ordered alphabetically: SELECT * FROM members ORDER BY name LIMIT 2; +------------+ | name | +------------+ | Immaculada | | Jagdish | +------------+ The third name, ordered alphabetically (the first name would be offset zero, so the third is offset two): SELECT * FROM members ORDER BY name LIMIT 2,1; +-------+ | name | +-------+ | Kenny | +-------+ From MariaDB 10.3.2, LIMIT can be used in a multi-table update: CREATE TABLE warehouse (product_id INT, qty INT); INSERT INTO warehouse VALUES (1,100),(2,100),(3,100),(4,100); CREATE TABLE store (product_id INT, qty INT); INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5); UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2, store.qty = store.qty+2 WHERE (warehouse.product_id = store.product_id AND store.product_id >= 1) ORDER BY store.product_id DESC LIMIT 2; SELECT * FROM warehouse; +------------+------+ | product_id | qty | +------------+------+ | 1 | 100 | | 2 | 100 | | 3 | 98 | | 4 | 98 | +------------+------+ SELECT * FROM store; +------------+------+ | product_id | qty | +------------+------+ | 1 | 5 | | 2 | 5 | | 3 | 7 | | 4 | 7 | +------------+------+ From MariaDB 10.3.3, LIMIT can be used with GROUP_CONCAT, so, for example, given the following table: CREATE TABLE d (dd DATE, cc INT); INSERT INTO d VALUES ('2017-01-01',1); INSERT INTO d VALUES ('2017-01-02',2); INSERT INTO d VALUES ('2017-01-04',3); the following query: SELECT SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) FROM d; +----------------------------------------------------------------------------+ | SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) | +----------------------------------------------------------------------------+ | 2017-01-04:3 | +----------------------------------------------------------------------------+ can be more simply rewritten as: SELECT GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) FROM d; +-------------------------------------------------------------+ | GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) | +-------------------------------------------------------------+ | 2017-01-04:3 | +-------------------------------------------------------------+ URL: https://mariadb.com/kb/en/limit/https://mariadb.com/kb/en/limit/] #LOAD XMLSyntax ------ LOAD XML [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name' [REPLACE | IGNORE] INTO TABLE [db_name.]tbl_name [CHARACTER SET charset_name] [ROWS IDENTIFIED BY ''] [IGNORE number {LINES | ROWS}] [(column_or_user_var,...)] [SET col_name = expr,...] Description ----------- The LOAD XML statement reads data from an XML file into a table. The file_name must be given as a literal string. The tagname in the optional ROWS IDENTIFIED BY clause must also be given as a literal string, and must be surrounded by angle brackets (< and >). LOAD XML acts as the complement of running the mysql client in XML output mode (that is, starting the client with the --xml option). To write data from a table to an XML file, use a command such as the following one from the system shell: shell> mysql --xml -e 'SELECT * FROM mytable' > file.xml To read the file back into a table, use LOAD XML INFILE. By default, the element is considered to be the equivalent of a database table row; this can be changed using the ROWS IDENTIFIED BY clause. This statement supports three different XML formats: Column names as attributes and column values as attribute values: Column names as tags and column values as the content of these tags: value1 value2 Column names are the name attributes of tags, and values are the contents of these tags: value1 value2 This is the format used by other tools, such as mysqldump. All 3 formats can be used in the same XML file; the import routine automatically detects the format for each row and interprets it correctly. Tags are matched based on the tag or attribute name and the column name. The following clauses work essentially the same way for LOAD XML as they do for LOAD DATA: LOW_PRIORITY or CONCURRENT LOCAL REPLACE or IGNORE CHARACTER SET (column_or_user_var,...) SET See LOAD DATA for more information about these clauses. The IGNORE number LINES or IGNORE number ROWS clause causes the first number rows in the XML file to be skipped. It is analogous to the LOAD DATA statement's IGNORE ... LINES clause. If the LOW_PRIORITY keyword is used, insertions are delayed until no other clients are reading from the table. The CONCURRENT keyword allowes the use of concurrent inserts. These clauses cannot be specified together. This statement activates INSERT triggers. URL: https://mariadb.com/kb/en/load-xml/https://mariadb.com/kb/en/load-xml/, R+LOAD DATA INFILESyntax ------ LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name' [REPLACE | IGNORE] INTO TABLE tbl_name [CHARACTER SET charset_name] [{FIELDS | COLUMNS} [TERMINATED BY 'string'] [[OPTIONALLY] ENCLOSED BY 'char'] [ESCAPED BY 'char'] ] [LINES [STARTING BY 'string'] [TERMINATED BY 'string'] ] [IGNORE number LINES] [(col_name_or_user_var,...)] [SET col_name = expr,...] Description ----------- Reads rows from a text file into the designated table on the database at a very high speed. The file name must be given as a literal string. Files are written to disk using the SELECT INTO OUTFILE statement. You can then read the files back into a table using the LOAD DATA INFILE statement. The FIELDS and LINES clauses are the same in both statements. These clauses are optional, but if both are specified then the FIELDS clause must precede LINES. In releases after MariaDB 5.5, LOAD DATA INFILE is unsafe for statement-based replication. Executing this statement activates INSERT triggers. REPLACE and IGNORE In cases where you load data from a file into a table that already contains data and has a Primary Key, you may encounter issues where the statement attempts to insert a row with a Primary Key that already exists. When this happens, the statement fails with Error 1064, protecting the data already on the table. In cases where you want MariaDB to overwrite duplicates, use the REPLACE keyword. The REPLACE keyword works like the REPLACE statement. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing Primary Key, it replaces the table data. That is, in the event of a conflict, it assumes the file contains the desired row. This operation can cause a degradation in load speed by a factor of 20 or more if the part that has already been loaded is larger than the capacity of the InnoDB Buffer Pool. This happens because it causes a lot of turnaround in the Buffer Pool. Use the IGNORE keyword when you want to skip any rows that contain a conflicting Primary Key. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing Primary Key, it ignores the addition request and moves on to the next. That is, in the event of a conflict, it assumes the table contains the desired row. LOCAL When you issue this statement, the Server attempts to read files from the host file system. Using the LOCAL keyword, the statement instead attempts to read files from the client. This allows you to insert files from the client's local file system into the database. In the event that you don't want the server to permit this operation, (such as for security reasons), you can disable support using local_infile. When this system variable is set to 0, MariaDB rejects LOAD DATA LOCAL INFILE statements, failing with an error message. Character-sets When the statement opens the file, it attempts to read the contents using the default character-set, as defined by the character_set_database system variable. In the cases where the file was written using a character-set other than the default, you can specify the character-set to use with the CHARACTER SET clause in the statement. It ignores character-sets specified by the SET NAMES statement and by the character_set_client system variable. Setting the CHARACTER SET clause to a value of binary indicates "no conversion." The statement interprets all fields in the file as having the same character-set, regardless of the column data type. To properly interpret file contents, you must ensure that it was written with the correct character-set. If you write a data file with mysqldump -T or with the SELECT INTO OUTFILE statement with the mysql client, be sure to use the --default-character-set option, so that the output is written with the desired character-set. When using mixed character sets, use the CHARACTER SET clause in both SELECT INTO OUTFILE and LOAD DATA INFILE to ensure that MariaDB correctly interprets the escape sequences. The character_set_filesystem system variable controls the interpretation of the filename. It is currently not possible to load data files that use the ucs2 character set. Priority and Concurrency In loading data from a file, there's a risk that the statement will attempt insertions concurrent with reads from another client, which can result in the read serving a result-set that contains only part of the update from the LOAD DATA INFILE statement. Using the LOW_PRIORITY keyword, MariaDB delays insertions until no other clients are reading from the table. Alternatively, you can use the CONCURRENT keyword to perform concurrent insertion. The LOW_PRIORITY and CONCURRENT keywords are mutually exclusive. They cannot be used in the same statement. Progress Reporting Since MariaDB 5.3, the LOAD DATA INFILE statement supports progress reporting. You may find this useful when dealing with long-running operations. Using another client you can issue a SHOW PROCESSLIST query to check the progress of the data load. Using mysqlimport MariaDB ships with a separate utility for loading data from files: mysqlimport. It operates by sending LOAD DATA INFILE statements to the server. Using mysqlimport you can compress the file using the --compress option, to get better performance over slow networks, providing both the client and server support the compressed protocol. Use the --local option to load from the local file system. Indexing In cases where the storage engine supports ALTER TABLE... DISABLE KEYS statements, the LOAD DATA INFILE statement automatically disables indexes during the execution. URL: https://mariadb.com/kb/en/load-data-infile/https://mariadb.com/kb/en/load-data-infile/ ) /( JNon-Recursive Common Table Expressions OverviewCommon Table Expressions (CTEs) are a standard SQL feature, and are essentially temporary named result sets. There are two kinds of CTEs: Non-Recursive, which this article covers; and Recursive. Common table expressions were introduced in MariaDB 10.2.1. Non-Recursive CTEs The WITH keyword signifies a CTE. It is given a name, followed by a body (the main query) as follows: CTEs are similar to derived tables. For example WITH engineers AS ( SELECT * FROM employees WHERE dept = 'Engineering' ) SELECT * FROM engineers WHERE ... SELECT * FROM ( SELECT * FROM employees WHERE dept = 'Engineering' ) AS engineers WHERE ... A non-recursive CTE is basically a query-local VIEW. There are several advantages and caveats to them. The syntax is more readable than nested FROM (SELECT ...). A CTE can refer to another and it can be referenced from multiple places. A CTE referencing Another CTE Using this format makes for a more readable SQL than a nested FROM(SELECT ...) clause. Below is an example of this: WITH engineers AS ( SELECT * FROM employees WHERE dept IN('Development','Support') ), eu_engineers AS ( SELECT * FROM engineers WHERE country IN('NL',...) ) SELECT ... FROM eu_engineers; Multiple Uses of a CTE This can be an 'anti-self join', for example: WITH engineers AS ( SELECT * FROM employees WHERE dept IN('Development','Support') ) SELECT * FROM engineers E1 WHERE NOT EXISTS (SELECT 1 FROM engineers E2 WHERE E2.country=E1.country AND E2.name E1.name ); Or, for year-over-year comparisons, for example: WITH sales_product_year AS ( SELECT product, YEAR(ship_date) AS year, SUM(price) AS total_amt FROM item_sales GROUP BY product, year ) SELECT * FROM sales_product_year CUR, sales_product_year PREV, WHERE CUR.product=PREV.product AND CUR.year=PREV.year + 1 AND CUR.total_amt > PREV.total_amt Another use is to compare individuals against their group. Below is an example of how this might be executed: WITH sales_product_year AS ( SELECT product, YEAR(ship_date) AS year, SUM(price) AS total_amt FROM item_sales GROUP BY product, year ) SELECT * FROM sales_product_year S1 WHERE total_amt > (SELECT 0.1 * SUM(total_amt) FROM sales_product_year S2 WHERE S2.year = S1.year) URL: https://mariadb.com/kb/en/non-recursive-common-table-expressions-overview/https://mariadb.com/kb/en/non-recursive-common-table-expressions-overview/ #ORDER BYDescription ----------- Use the ORDER BY clause to order a resultset, such as that are returned from a SELECT statement. You can specify just a column or use any expression with functions. If you are using the GROUP BY clause, you can use grouping functions in ORDER BY. Ordering is done after grouping. You can use multiple ordering expressions, separated by commas. Rows will be sorted by the first expression, then by the second expression if they have the same value for the first, and so on. You can use the keywords ASC and DESC after each ordering expression to force that ordering to be ascending or descending, respectively. Ordering is ascending by default. You can also use a single integer as the ordering expression. If you use an integer n, the results will be ordered by the nth column in the select expression. When string values are compared, they are compared as if by the STRCMP function. STRCMP ignores trailing whitespace and may normalize characters and ignore case, depending on the collation in use. Starting from MariaDB 5.5.35 duplicated entries in the ORDER BY clause are removed. MySQL 5.6 also removes duplicated fields. ORDER BY can also be used to order the activities of a DELETE or UPDATE statement (usually with the LIMIT clause). Until MariaDB 10.3.1, it was not possible to use ORDER BY (or LIMIT) in a multi-table UPDATE statement. This restriction was lifted in MariaDB 10.3.2. Examples -------- CREATE TABLE seq (i INT, x VARCHAR(1)); INSERT INTO seq VALUES (1,'a'), (2,'b'), (3,'b'), (4,'f'), (5,'e'); SELECT * FROM seq ORDER BY i; +------+------+ | i | x | +------+------+ | 1 | a | | 2 | b | | 3 | b | | 4 | f | | 5 | e | +------+------+ SELECT * FROM seq ORDER BY i DESC; +------+------+ | i | x | +------+------+ | 5 | e | | 4 | f | | 3 | b | | 2 | b | | 1 | a | +------+------+ SELECT * FROM seq ORDER BY x,i; +------+------+ | i | x | +------+------+ | 1 | a | | 2 | b | | 3 | b | | 5 | e | | 4 | f | +------+------+ ORDER BY in an UPDATE statement, in conjunction with LIMIT: UPDATE seq SET x='z' WHERE x='b' ORDER BY i DESC LIMIT 1; SELECT * FROM seq; +------+------+ | i | x | +------+------+ | 1 | a | | 2 | b | | 3 | z | | 4 | f | | 5 | e | +------+------+ From MariaDB 10.3.2, ORDER BY can be used in a multi-table update: CREATE TABLE warehouse (product_id INT, qty INT); INSERT INTO warehouse VALUES (1,100),(2,100),(3,100),(4,100); CREATE TABLE store (product_id INT, qty INT); INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5); UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2, store.qty = store.qty+2 WHERE (warehouse.product_id = store.product_id AND store.product_id >= 1) ORDER BY store.product_id DESC LIMIT 2; SELECT * FROM warehouse; +------------+------+ | product_id | qty | +------------+------+ | 1 | 100 | | 2 | 100 | | 3 | 98 | | 4 | 98 | +------------+------+ SELECT * FROM store; +------------+------+ | product_id | qty | +------------+------+ | 1 | 5 | | 2 | 5 | | 3 | 7 | | 4 | 7 | +------------+------+ URL: https://mariadb.com/kb/en/order-by/https://mariadb.com/kb/en/order-by/ K J|+FRecursive Common Table Expressions OverviewRecursive Common Table Expressions have been supported since MariaDB 10.2.2. Common Table Expressions (CTEs) are a standard SQL feature, and are essentially temporary named result sets. CTEs first appeared in the SQL standard in 1999, and the first implementations began appearing in 2007. There are two kinds of CTEs: Non-recursive Recursive, which this article covers. SQL is generally poor at recursive structures. CTEs permit a query to reference itself. A recursive CTE will repeatedly execute subsets of the data until it obtains the complete result set. This makes it particularly useful for handing hierarchical or tree-structured data. Syntax example WITH RECURSIVE signifies a recursive CTE. It is given a name, followed by a body (the main query) as follows: Computation Given the following structure: First execute the anchor part of the query: Next, execute the recursive part of the query: Summary so far with recursive R as ( select anchor_data union [all] select recursive_part from R, ... ) select ... Compute anchor_data Compute recursive_part to get the new data if (new data is non-empty) goto 2; CAST to avoid truncating data As currently implemented by MariaDB and by the SQL Standard, data may be truncated if not correctly cast. It is necessary to CAST the column to the correct width if the CTE's recursive part produces wider values for a column than the CTE's nonrecursive part. Some other DBMS give an error in this situation, and MariaDB's behavior may change in future - see MDEV-12325. See the examples below. Examples -------- Transitive closure - determining bus destinations Sample data: CREATE TABLE bus_routes (origin varchar(50), dst varchar(50)); INSERT INTO bus_routes VALUES ('New York', 'Boston'), ('Boston', 'New York'), ('New York', 'Washington'), ('Washington', 'Boston'), ('Washington', 'Raleigh'); Now, we want to return the bus destinations with New York as the origin: WITH RECURSIVE bus_dst as ( SELECT origin as dst FROM bus_routes WHERE origin='New York' UNION SELECT bus_routes.dst FROM bus_routes, bus_dst WHERE bus_dst.dst= bus_routes.origin ) SELECT * FROM bus_dst; +------------+ | dst | +------------+ | New York | | Boston | | Washington | | Raleigh | +------------+ The above example is computed as follows: First, the anchor data is calculated: Starting from New York Boston and Washington are added Next, the recursive part: Starting from Boston and then Washington Raleigh is added UNION excludes nodes that are already present. Computing paths - determining bus routes This time, we are trying to get bus routes such as “New York -> Washington -> Raleigh”. Using the same sample data as the previous example: WITH RECURSIVE paths (cur_path, cur_dest) AS ( SELECT origin, origin FROM bus_routes WHERE origin='New York' UNION SELECT CONCAT(paths.cur_path, ',', bus_routes.dst), bus_routes.dst FROM paths, bus_routes WHERE paths.cur_dest = bus_routes.origin AND LOCATE(bus_routes.dst, paths.cur_path)=0 ) SELECT * FROM paths; +-----------------------------+------------+ | cur_path | cur_dest | +-----------------------------+------------+ | New York | New York | | New York,Boston | Boston | | New York,Washington | Washington | | New York,Washington,Boston | Boston | | New York,Washington,Raleigh | Raleigh | +-----------------------------+------------+ CAST to avoid data truncation In the following example, data is truncated because the results are not specifically cast to a wide enough type: WITH RECURSIVE tbl AS ( SELECT NULL AS col UNION SELECT "THIS NEVER SHOWS UP" AS col FROM tbl ) +------+ | col | +------+ | NULL | | | +------+ Explicitly use CAST to overcome this: WITH RECURSIVE tbl AS ( SELECT CAST(NULL AS CHAR(50)) AS col UNION SELECT "THIS NEVER SHOWS UP" AS col FROM tbl ) SELECT * FROM tbl; +---------------------+ | col | +---------------------+ | NULL | | THIS NEVER SHOWS UP | +---------------------+ URL: https://mariadb.com/kb/en/recursive-common-table-expressions-overview/https://mariadb.com/kb/en/recursive-common-table-expressions-overview/ "REPLACESyntax ------ REPLACE [LOW_PRIORITY | DELAYED] [INTO] tbl_name [PARTITION (partition_list)] [(col,...)] {VALUES | VALUE} ({expr | DEFAULT},...),(...),... Or: REPLACE [LOW_PRIORITY | DELAYED] [INTO] tbl_name [PARTITION (partition_list)] SET col={expr | DEFAULT}, ... Or: REPLACE [LOW_PRIORITY | DELAYED] [INTO] tbl_name [PARTITION (partition_list)] [(col,...)] SELECT ... Description ----------- REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted. If the table has more than one UNIQUE keys, it is possible that the new row conflicts with more than one row. In this case, all conflicting rows will be deleted. The table name can be specified in the form db_name.tbl_name or, if a default database is selected, in the form tbl_name (see Identifier Qualifiers). This allows to use REPLACE ... SELECT to copy rows between different databases. Basically it works like this: BEGIN; SELECT 1 FROM t1 WHERE key=# FOR UPDATE; IF found-row DELETE FROM t1 WHERE key=# ; INSERT INTO t1 VALUES (...); ENDIF END; The above can be replaced with: REPLACE INTO t1 VALUES (...) REPLACE is a MariaDB/MySQL extension to the SQL standard. It either inserts, or deletes and inserts. For other MariaDB/MySQL extensions to standard SQL --- that also handle duplicate values --- see IGNORE and INSERT ON DUPLICATE KEY UPDATE. Note that unless the table has a PRIMARY KEY or UNIQUE index, using a REPLACE statement makes no sense. It becomes equivalent to INSERT, because there is no index to be used to determine whether a new row duplicates another. Values for all columns are taken from the values specified in the REPLACE statement. Any missing columns are set to their default values, just as happens for INSERT. You cannot refer to values from the current row and use them in the new row. If you use an assignment such as 'SET col = col + 1', the reference to the column name on the right hand side is treated as DEFAULT(col), so the assignment is equivalent to 'SET col = DEFAULT(col) + 1'. To use REPLACE, you must have both the INSERT and DELETE privileges for the table. There are some gotchas you should be aware of, before using REPLACE: If there is an AUTO_INCREMENT field, a new value will be generated. If there are foreign keys, ON DELETE action will be activated by REPLACE. Triggers on DELETE and INSERT will be activated by REPLACE. To avoid some of these behaviors, you can use INSERT ... ON DUPLICATE KEY UPDATE. The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details. This statement activates INSERT and DELETE triggers. See Trigger Overview for details. URL: https://mariadb.com/kb/en/replace/https://mariadb.com/kb/en/replace/T ;z !SELECTSyntax ------ SELECT [ALL | DISTINCT | DISTINCTROW] [HIGH_PRIORITY] [STRAIGHT_JOIN] [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT] [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS] select_expr [, select_expr ...] [ FROM table_references [WHERE where_condition] [GROUP BY {col_name | expr | position} [ASC | DESC], ... [WITH ROLLUP]] [HAVING where_condition] [ORDER BY {col_name | expr | position} [ASC | DESC], ...] [LIMIT {[offset,] row_count | row_count OFFSET offset}] procedure|[PROCEDURE procedure_name(argument_list)] [INTO OUTFILE 'file_name' [CHARACTER SET charset_name] [export_options] INTO DUMPFILE 'file_name' | INTO var_name [, var_name] ] | [[FOR UPDATE | LOCK IN SHARE MODE] [WAIT n | NOWAIT] ] ] export_options: [{FIELDS | COLUMNS} [TERMINATED BY 'string'] [[OPTIONALLY] ENCLOSED BY 'char'] [ESCAPED BY 'char'] ] [LINES [STARTING BY 'string'] [TERMINATED BY 'string'] ] Description ----------- SELECT is used to retrieve rows selected from one or more tables, and can include UNION statements and subqueries. Each select_expr expression indicates a column or data that you want to retrieve. You must have at least one select expression. See Select Expressions below. The FROM clause indicates the table or tables from which to retrieve rows. Use either a single table name or a JOIN expression. See JOIN for details. If no table is involved, FROM DUAL can be specified. The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details. Each table can also be specified as db_name.tabl_name. Each column can also be specified as tbl_name.col_name or even db_name.tbl_name.col_name. This allows to write queries which involve multiple databases. See Identifier Qualifiers for syntax details. The WHERE clause, if given, indicates the condition or conditions that rows must satisfy to be selected. where_condition is an expression that evaluates to true for each row to be selected. The statement selects all rows if there is no WHERE clause. In the WHERE clause, you can use any of the functions and operators that MariaDB supports, except for aggregate (summary) functions. See Functions and Operators and Functions and Modifiers for use with GROUP BY (aggregate). Use the ORDER BY clause to order the results. Use the LIMIT clause allows you to restrict the results to only a certain number of rows, optionally with an offset. Use the GROUP BY and HAVING clauses to group rows together when they have columns or computed values in common. SELECT can also be used to retrieve rows computed without reference to any table. Select Expressions A SELECT statement must contain one or more select expressions, separated by commas. Each select expression can be one of the following: The name of a column. Any expression using functions and operators. * to select all columns from all tables in the FROM clause. tbl_name.* to select all columns from just the table tbl_name. When specifying a column, you can either use just the column name or qualify the column name with the name of the table using tbl_name.col_name. The qualified form is useful if you are joining multiple tables in the FROM clause. If you do not qualify the column names when selecting from multiple tables, MariaDB will try to find the column in each table. It is an error if that column name exists in multiple tables. You can quote column names using backticks. If you are qualifying column names with table names, quote each part separately as `tbl_name`.`col_name`. If you use any grouping functions in any of the select expressions, all rows in your results will be implicitly grouped, as if you had used GROUP BY NULL. DISTINCT A query may produce some identical rows. By default, all rows are retrieved, even when their values are the same. To explicitly specify that you want to retrieve identical rows, use the ALL option. If you want duplicates to be removed from the resultset, use the DISTINCT option. DISTINCTROW is a synonym for DISTINCT. See also COUNT DISTINCT and SELECT UNIQUE in Oracle mode. INTO The INTO clause is used to specify that the query results should be written to a file or variable. SELECT INTO OUTFILE - formatting and writing the result to an external file. SELECT INTO DUMPFILE - binary-safe writing of the unformatted results to an external file. SELECT INTO Variable - selecting and setting variables. The reverse of SELECT INTO OUTFILE is LOAD DATA. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. PROCEDURE Passes the whole result set to a C Procedure. See PROCEDURE and PROCEDURE ANALYSE (the only built-in procedure not requiring the server to be recompiled). max_statement_time clause By using max_statement_time in conjunction with SET STATEMENT, it is possible to limit the execution time of individual queries. For example: SET STATEMENT max_statement_time=100 FOR SELECT field1 FROM table_name ORDER BY field1; URL: https://mariadb.com/kb/en/select/https://mariadb.com/kb/en/select/ ngXi /SELECT INTO DUMPFILESyntax ------ SELECT ... INTO DUMPFILE 'file_path' Description ----------- SELECT ... INTO DUMPFILE is a SELECT clause which writes the resultset into a single unformatted row, without any separators, in a file. The results will not be returned to the client. file_path can be an absolute path, or a relative path starting from the data directory. It can only be specified as a string literal, not as a variable. However, the statement can be dynamically composed and executed as a prepared statement to work around this limitation. This statement is binary-safe and so is particularly useful for writing BLOB values to file. It can be used, for example, to copy an image or an audio document from the database to a file. SELECT ... INTO FILE can be used to save a text file. The file must not exist. It cannot be overwritten. A user needs the FILE privilege to run this statement. Also, MariaDB needs permission to write files in the specified location. If the secure_file_priv system variable is set to a non-empty directory name, the file can only be written to that directory. Since MariaDB 5.1, the character_set_filesystem system variable has controlled interpretation of file names that are given as literal strings. Example SELECT _utf8'Hello world!' INTO DUMPFILE '/tmp/world'; SELECT LOAD_FILE('/tmp/world') AS world; +--------------+ | world | +--------------+ | Hello world! | +--------------+ URL: https://mariadb.com/kb/en/select-into-dumpfile/https://mariadb.com/kb/en/select-into-dumpfile/S.SELECT INTO OUTFILESyntax ------ SELECT ... INTO OUTFILE 'file_name' [CHARACTER SET charset_name] [export_options] export_options: [{FIELDS | COLUMNS} [TERMINATED BY 'string'] [[OPTIONALLY] ENCLOSED BY 'char'] [ESCAPED BY 'char'] ] [LINES [STARTING BY 'string'] [TERMINATED BY 'string'] ] Description ----------- SELECT INTO OUTFILE writes the resulting rows to a file, and allows the use of column and row terminators to specify a particular output format. The default is to terminate fields with tabs (\t) and lines with newlines (\n). The file must not exist. It cannot be overwritten. A user needs the FILE privilege to run this statement. Also, MariaDB needs permission to write files in the specified location. If the secure_file_priv system variable is set to a non-empty directory name, the file can only be written to that directory. The LOAD DATA INFILE statement complements SELECT INTO OUTFILE. Character-sets The CHARACTER SET clause specifies the character set in which the results are to be written. Without the clause, no conversion takes place (the binary character set). In this case, if there are multiple character sets, the output will contain these too, and may not easily be able to be reloaded. In cases where you have two servers using different character-sets, using SELECT INTO OUTFILE to transfer data from one to the other can have unexpected results. To ensure that MariaDB correctly interprets the escape sequences, use the CHARACTER SET clause on both the SELECT INTO OUTFILE statement and the subsequent LOAD DATA INFILE statement. Example The following example produces a file in the CSV format: SELECT customer_id, firstname, surname INTO OUTFILE '/exportdata/customers.txt' FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY '\n' FROM customers; URL: https://mariadb.com/kb/en/select-into-outfile/https://mariadb.com/kb/en/select-into-outfile/WITHThe WITH keyword signifies a Common Table Expression (CTE). It allows you to refer to a subquery expression many times in a query, as if having a temporary table that only exists for the duration of a query. There are two kinds of CTEs: Non-Recursive Recursive Common Table Expression WITH was introduced in MariaDB 10.2.1. Recursive WITH has been supported since MariaDB 10.2.2. Syntax ------ WITH [RECURSIVE] table_reference as (SELECT ...) SELECT ... You can use table_reference as any normal table in the external SELECT part. You can also use WITH in sub queries. WITH can also be used with EXPLAIN and SELECT. Below is an example with the WITH at the top level: WITH t AS (SELECT a FROM t1 WHERE b >= 'c') SELECT * FROM t2, t WHERE t2.c = t.a; The example below uses WITH in a subquery: SELECT t1.a, t1.b FROM t1, t2 WHERE t1.a > t2.c AND t2.c IN(WITH t AS (SELECT * FROM t1 WHERE t1.a URL: https://mariadb.com/kb/en/with/https://mariadb.com/kb/en/with/^#DESCRIBESyntax ------ {DESCRIBE | DESC} tbl_name [col_name | wild] Description ----------- DESCRIBE provides information about the columns in a table. It is a shortcut for SHOW COLUMNS FROM. These statements also display information for views. col_name can be a column name, or a string containing the SQL "%" and "_" wildcard characters to obtain output only for the columns with names matching the string. There is no need to enclose the string within quotes unless it contains spaces or other special characters. DESCRIBE city; +------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+----------+------+-----+---------+----------------+ | Id | int(11) | NO | PRI | NULL | auto_increment | | Name | char(35) | YES | | NULL | | | Country | char(3) | NO | UNI | | | | District | char(20) | YES | MUL | | | | Population | int(11) | YES | | NULL | | +------------+----------+------+-----+---------+----------------+ The description for SHOW COLUMNS provides more information about the output columns. URL: https://mariadb.com/kb/en/describe/https://mariadb.com/kb/en/describe/ ' Ϋ-SELECT WITH ROLLUPSyntax ------ See SELECT for the full syntax. Description ----------- The WITH ROLLUP modifier adds extra rows to the resultset that represent super-aggregate summaries. The super-aggregated column is represented by a NULL value. Multiple aggregates over different columns will be added if there are multiple GROUP BY columns. The LIMIT clause can be used at the same time, and is applied after the WITH ROLLUP rows have been added. WITH ROLLUP cannot be used with ORDER BY. Some sorting is still possible by using ASC or DESC clauses with the GROUP BY column, although the super-aggregate rows will always be added last. Examples -------- These examples use the following sample table CREATE TABLE booksales ( country VARCHAR(35), genre ENUM('fiction','non-fiction'), year YEAR, sales INT); INSERT INTO booksales VALUES ('Senegal','fiction',2014,12234), ('Senegal','fiction',2015,15647), ('Senegal','non-fiction',2014,64980), ('Senegal','non-fiction',2015,78901), ('Paraguay','fiction',2014,87970), ('Paraguay','fiction',2015,76940), ('Paraguay','non-fiction',2014,8760), ('Paraguay','non-fiction',2015,9030); The addition of the WITH ROLLUP modifier in this example adds an extra row that aggregates both years: SELECT year, SUM(sales) FROM booksales GROUP BY year; +------+------------+ | year | SUM(sales) | +------+------------+ | 2014 | 173944 | | 2015 | 180518 | +------+------------+ 2 rows in set (0.08 sec) SELECT year, SUM(sales) FROM booksales GROUP BY year WITH ROLLUP; +------+------------+ | year | SUM(sales) | +------+------------+ | 2014 | 173944 | | 2015 | 180518 | | NULL | 354462 | +------+------------+ In the following example, each time the genre, the year or the country change, another super-aggregate row is added: SELECT country, year, genre, SUM(sales) FROM booksales GROUP BY country, year, genre; +----------+------+-------------+------------+ | country | year | genre | SUM(sales) | +----------+------+-------------+------------+ | Paraguay | 2014 | fiction | 87970 | | Paraguay | 2014 | non-fiction | 8760 | | Paraguay | 2015 | fiction | 76940 | | Paraguay | 2015 | non-fiction | 9030 | | Senegal | 2014 | fiction | 12234 | | Senegal | 2014 | non-fiction | 64980 | | Senegal | 2015 | fiction | 15647 | | Senegal | 2015 | non-fiction | 78901 | +----------+------+-------------+------------+ SELECT country, year, genre, SUM(sales) FROM booksales GROUP BY country, year, genre WITH ROLLUP; +----------+------+-------------+------------+ | country | year | genre | SUM(sales) | +----------+------+-------------+------------+ | Paraguay | 2014 | fiction | 87970 | | Paraguay | 2014 | non-fiction | 8760 | | Paraguay | 2014 | NULL | 96730 | | Paraguay | 2015 | fiction | 76940 | | Paraguay | 2015 | non-fiction | 9030 | | Paraguay | 2015 | NULL | 85970 | | Paraguay | NULL | NULL | 182700 | | Senegal | 2014 | fiction | 12234 | | Senegal | 2014 | non-fiction | 64980 | | Senegal | 2014 | NULL | 77214 | | Senegal | 2015 | fiction | 15647 | | Senegal | 2015 | non-fiction | 78901 | | Senegal | 2015 | NULL | 94548 | | Senegal | NULL | NULL | 171762 | | NULL | NULL | NULL | 354462 | +----------+------+-------------+------------+ The LIMIT clause, applied after WITH ROLLUP: SELECT country, year, genre, SUM(sales) FROM booksales GROUP BY country, year, genre WITH ROLLUP LIMIT 4; +----------+------+-------------+------------+ | country | year | genre | SUM(sales) | +----------+------+-------------+------------+ | Paraguay | 2014 | fiction | 87970 | | Paraguay | 2014 | non-fiction | 8760 | | Paraguay | 2014 | NULL | 96730 | | Paraguay | 2015 | fiction | 76940 | +----------+------+-------------+------------+ Sorting by year descending: SELECT country, year, genre, SUM(sales) FROM booksales GROUP BY country, year DESC, genre WITH ROLLUP; +----------+------+-------------+------------+ | country | year | genre | SUM(sales) | +----------+------+-------------+------------+ | Paraguay | 2015 | fiction | 76940 | | Paraguay | 2015 | non-fiction | 9030 | | Paraguay | 2015 | NULL | 85970 | | Paraguay | 2014 | fiction | 87970 | | Paraguay | 2014 | non-fiction | 8760 | | Paraguay | 2014 | NULL | 96730 | | Paraguay | NULL | NULL | 182700 | | Senegal | 2015 | fiction | 15647 | | Senegal | 2015 | non-fiction | 78901 | | Senegal | 2015 | NULL | 94548 | | Senegal | 2014 | fiction | 12234 | | Senegal | 2014 | non-fiction | 64980 | | Senegal | 2014 | NULL | 77214 | | Senegal | NULL | NULL | 171762 | | NULL | NULL | NULL | 354462 | +----------+------+-------------+------------+ URL: https://mariadb.com/kb/en/select-with-rollup/https://mariadb.com/kb/en/select-with-rollup/.ANALYZE FORMAT=JSONANALYZE FORMAT=JSON is a mix of the EXPLAIN FORMAT=JSON and ANALYZE statement features. ANALYZE FORMAT=JSON $statement will execute $statement, and then print the output of EXPLAIN FORMAT=JSON, amended with the data from query execution. Basic Execution Data You can get the following also from tabular ANALYZE statement form: r_rows is provided for any node that reads rows. It shows how many rows were read, on average r_filtered is provided whenever there is a condition that is checked. It shows the percentage of rows left after checking the condition. Advanced Execution Data The most important data that is not available in tabula ANALYZE statement are: r_loops field. This shows how many times the node was executed. Most query plan elements have this field. r_total_time_ms field. It shows how much time in total was spent executing this node. If the node has subnodes, their execution time is included. r_buffer_size field. Query plan nodes that make use of buffers report the size of buffer that was was used. Data About Individual Query Plan Nodes filesort node reports whether sorting was done with LIMIT n parameter, and how many rows were in the sort result. block-nl-join node has r_loops field, which allows to tell whether Using join buffer was efficient range-checked-for-each-record reports counters that show the result of the check. expression-cache is used for subqueries, and it reports how many times the cache was used, and what cache hit ratio was. union_result node has r_rows so one can see how many rows were produced after UNION operation and so forth Use Cases See Examples of ANALYZE FORMAT=JSON. URL: https://mariadb.com/kb/en/analyze-format-json/https://mariadb.com/kb/en/analyze-format-json/h \߰ , UNIONUNION is used to combine the results from multiple SELECT statements into a single result set. Syntax ------ SELECT ... UNION [ALL | DISTINCT] SELECT ... [UNION [ALL | DISTINCT] SELECT ...] [ORDER BY [column [, column ...]]] [LIMIT {[offset,] row_count | row_count OFFSET offset}] Description ----------- UNION is used to combine the results from multiple SELECT statements into a single result set. The column names from the first SELECT statement are used as the column names for the results returned. Selected columns listed in corresponding positions of each SELECT statement should have the same data type. (For example, the first column selected by the first statement should have the same type as the first column selected by the other statements.) If they don't, the type and length of the columns in the result take into account the values returned by all of the SELECTs, so there is no need for explicit casting. Note that currently this is not the case for recursive CTEs - see MDEV-12325. Table names can be specified as db_name.tbl_name. This permits writing UNIONs which involve multiple databases. See Identifier Qualifiers for syntax details. UNION queries cannot be used with aggregate functions. ALL/DISTINCT The ALL keyword causes duplicate rows to be preserved. The DISTINCT keyword (the default if the keyword is omitted) causes duplicate rows to be removed by the results. UNION ALL and UNION DISTINCT can both be present in a query. In this case, UNION DISTINCT will override any UNION ALLs to its left. Until MariaDB 10.1.1, all UNION ALL statements required the server to create a temporary table. Since MariaDB 10.1.1, the server can in most cases execute UNION ALL without creating a temporary table, improving performance (see MDEV-334). ORDER BY and LIMIT Individual SELECTs can contain their own ORDER BY and LIMIT clauses. In this case, the individual queries need to be wrapped between parentheses. However, this does not affect the order of the UNION, so they only are useful to limit the record read by one SELECT. The UNION can have global ORDER BY and LIMIT clauses, which affect the whole resultset. If the columns retrieved by individual SELECT statements have an alias (AS), the ORDER BY must use that alias, not the real column names. HIGH_PRIORITY Specifying a query as HIGH_PRIORITY will not work inside a UNION. If applied to the first SELECT, it will be ignored. Applying to a later SELECT results in a syntax error: ERROR 1234 (42000): Incorrect usage/placement of 'HIGH_PRIORITY' SELECT ... INTO ... Individual SELECTs cannot be written INTO DUMPFILE or INTO OUTFILE. If the last SELECT statement specifies INTO DUMPFILE or INTO OUTFILE, the entire result of the UNION will be written. Placing the clause after any other SELECT will result in a syntax error. If the result is a single row, SELECT ... INTO @var_name can also be used. Parentheses From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned. Examples -------- UNION between tables having different column names: (SELECT e_name AS name, email FROM employees) UNION (SELECT c_name AS name, email FROM customers); Specifying the UNION's global order and limiting total rows: (SELECT name, email FROM employees) UNION (SELECT name, email FROM customers) ORDER BY name LIMIT 10; Adding a constant row: (SELECT 'John Doe' AS name, 'john.doe@example.net' AS email) UNION (SELECT name, email FROM customers); Differing types: SELECT CAST('x' AS CHAR(1)) UNION SELECT REPEAT('y',4); +----------------------+ | CAST('x' AS CHAR(1)) | +----------------------+ | x | | yyyy | +----------------------+ Returning the results in order of each individual SELECT by use of a sort column: (SELECT 1 AS sort_column, e_name AS name, email FROM employees) UNION (SELECT 2, c_name AS name, email FROM customers) ORDER BY sort_column; Difference between UNION, EXCEPT and INTERSECT: CREATE TABLE seqs (i INT); INSERT INTO seqs VALUES (1),(2),(3),(4),(5),(6); SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 1 | | 2 | | 3 | | 4 | | 5 | | 6 | +------+ SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 1 | | 2 | +------+ SELECT i FROM seqs WHERE i =3; +------+ | i | +------+ | 3 | +------+ Parentheses for specifying precedence, from MariaDB 10.4.0 CREATE OR REPLACE TABLE t1 (a INT); CREATE OR REPLACE TABLE t2 (b INT); CREATE OR REPLACE TABLE t3 (c INT); INSERT INTO t1 VALUES (1),(2),(3),(4); INSERT INTO t2 VALUES (5),(6); INSERT INTO t3 VALUES (1),(6); ((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT (SELECT c FROM t3); +------+ | a | +------+ | 1 | | 6 | +------+ (SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT (SELECT c FROM t3)); +------+ | a | +------+ | 1 | | 2 | | 3 | | 4 | | 6 | +------+ URL: https://mariadb.com/kb/en/union/https://mariadb.com/kb/en/union/ _Hns !UPDATESyntax ------ Single-table syntax: UPDATE [LOW_PRIORITY] [IGNORE] table_reference [PARTITION (partition_list)] SET col1={expr1|DEFAULT} [,col2={expr2|DEFAULT}] ... [WHERE where_condition] [ORDER BY ...] [LIMIT row_count] Multiple-table syntax: UPDATE [LOW_PRIORITY] [IGNORE] table_references SET col1={expr1|DEFAULT} [, col2={expr2|DEFAULT}] ... [WHERE where_condition] Description ----------- For the single-table syntax, the UPDATE statement updates columns of existing rows in the named table with new values. The SET clause indicates which columns to modify and the values they should be given. Each value can be given as an expression, or the keyword DEFAULT to set a column explicitly to its default value. The WHERE clause, if given, specifies the conditions that identify which rows to update. With no WHERE clause, all rows are updated. If the ORDER BY clause is specified, the rows are updated in the order that is specified. The LIMIT clause places a limit on the number of rows that can be updated. The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details. Until MariaDB 10.3.2, for the multiple-table syntax, UPDATE updates rows in each table named in table_references that satisfy the conditions. In this case, ORDER BY and LIMIT cannot be used. This restriction was lifted in MariaDB 10.3.2 and both clauses can be used with multiple-table updates. An UPDATE can also reference tables which are located in different databases; see Identifier Qualifiers for the syntax. where_condition is an expression that evaluates to true for each row to be updated. table_references and where_condition are as specified as described in SELECT. Assignments are evaluated in left-to-right order, unless the SIMULTANEOUS_ASSIGNMENT sql_mode (available from MariaDB 10.3.5) is set, in which case the UPDATE statement evaluates all assignments simultaneously. You need the UPDATE privilege only for columns referenced in an UPDATE that are actually updated. You need only the SELECT privilege for any columns that are read but not modified. See GRANT. The UPDATE statement supports the following modifiers: If you use the LOW_PRIORITY keyword, execution of the UPDATE is delayed until no other clients are reading from the table. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). See HIGH_PRIORITY and LOW_PRIORITY clauses for details. If you use the IGNORE keyword, the update statement does not abort even if errors occur during the update. Rows for which duplicate-key conflicts occur are not updated. Rows for which columns are updated to values that would cause data conversion errors are updated to the closest valid values instead. UPDATE Statements With the Same Source and Target From MariaDB 10.3.2, UPDATE statements may have the same source and target. For example, given the following table: DROP TABLE t1; CREATE TABLE t1 (c1 INT, c2 INT); INSERT INTO t1 VALUES (10,10), (20,20); Until MariaDB 10.3.1, the following UPDATE statement would not work: UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1); ERROR 1093 (HY000): Table 't1' is specified twice, both as a target for 'UPDATE' and as a separate source for data From MariaDB 10.3.2, the statement executes successfully: UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1); SELECT * FROM t1; +------+------+ | c1 | c2 | +------+------+ | 10 | 10 | | 21 | 20 | +------+------+ Example Single-table syntax: UPDATE table_name SET column1 = value1, column2 = value2 WHERE id=100; Multiple-table syntax: UPDATE tab1, tab2 SET tab1.column1 = value1, tab1.column2 = value2 WHERE tab1.id = tab2.id; URL: https://mariadb.com/kb/en/update/https://mariadb.com/kb/en/update/(6ANALYZE FORMAT=JSON ExamplesExample #1 Customers who have ordered more than 1M goods. ANALYZE FORMAT=JSON SELECT CONT(*) FROM customer WHERE (SELECT SUM(o_totalprice) FROM orders WHERE o_custkey=c_custkey) > 1000*1000; The query takes 40 seconds over cold cache EXPLAIN: { "query_block": { "select_id": 1, "r_loops": 1, "r_total_time_ms": 39872, "table": { "table_name": "customer", "access_type": "index", "key": "i_c_nationkey", "key_length": "5", "used_key_parts": ["c_nationkey"], "r_loops": 1, "rows": 150303, "r_rows": 150000, "r_total_time_ms": 270.3, "filtered": 100, "r_filtered": 60.691, "attached_condition": "((subquery#2) > ((1000 * 1000)))", "using_index": true }, "subqueries": [ { "query_block": { "select_id": 2, "r_loops": 150000, "r_total_time_ms": 39531, "table": { "table_name": "orders", "access_type": "ref", "possible_keys": ["i_o_custkey"], "key": "i_o_custkey", "key_length": "5", "used_key_parts": ["o_custkey"], "ref": ["dbt3sf1.customer.c_custkey"], "r_loops": 150000, "rows": 7, "r_rows": 10, "r_total_time_ms": 39208, "filtered": 100, "r_filtered": 100 } } } ] } } ANALYZE shows that 39.2 seconds were spent in the subquery, which was executed 150K times (for every row of outer table). URL: https://mariadb.com/kb/en/analyze-formatjson-examples/https://mariadb.com/kb/en/analyze-formatjson-examples/ ` !,ANALYZE StatementThe ANALYZE statement was introduced in MariaDB 10.1.0. Description ----------- The ANALYZE statement is similar to the EXPLAIN statement. ANALYZE statement will invoke the optimizer, execute the statement, and then produce EXPLAIN output instead of the result set. The EXPLAIN output will be annotated with statistics from statement execution. This lets one check how close the optimizer's estimates about the query plan are to the reality. ANALYZE produces an overview, while the ANALYZE FORMAT=JSON command provides a more detailed view of the query plan and the query execution. The syntax is ANALYZE explainable_statement; where the statement is any statement for which one can run EXPLAIN. Command Output Consider an example: ANALYZE SELECT * FROM tbl1 WHERE key1 BETWEEN 10 AND 200 AND col1 LIKE 'foo%'\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: tbl1 type: range possible_keys: key1 key: key1 key_len: 5 ref: NULL rows: 181 r_rows: 181 filtered: 100.00 r_filtered: 10.50 Extra: Using index condition; Using where Compared to EXPLAIN, ANALYZE produces two extra columns: r_rows is an observation-based counterpart of the rows column. It shows how many rows were actually read from the table. r_filtered is an observation-based counterpart of the filtered column. It shows which fraction of rows was left after applying the WHERE condition. Interpreting the Output Joins Let's consider a more complicated example. ANALYZE SELECT * FROM orders, customer WHERE customer.c_custkey=orders.o_custkey AND customer.c_acctbal 200*1000 +----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | r_rows | filtered | r_filtered | Extra | +----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+ | 1 | SIMPLE | customer | ALL | PRIMARY,... | NULL | NULL | NULL | 149095 | 150000 | 18.08 | 9.13 | Using where | | 1 | SIMPLE | orders | ref | i_o_custkey | i_o_custkey | 5 | customer.c_custkey | 7 | 10 | 100.00 | 30.03 | Using where | +----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+ Here, one can see that For table customer, customer.rows=149095, customer.r_rows=150000. The estimate for number of rows we will read was fairly precise customer.filtered=18.08, customer.r_filtered=9.13. The optimizer somewhat overestimated the number of records that will match selectivity of condition attached to `customer` table (in general, when you have a full scan and r_filtered is less than 15%, it's time to consider adding an appropriate index). For table orders, orders.rows=7, orders.r_rows=10. This means that on average, there are 7 orders for a given c_custkey, but in our case there were 10, which is close to the expectation (when this number is consistently far from the expectation, it may be time to run ANALYZE TABLE, or even edit the table statistics manually to get better query plans). orders.filtered=100, orders.r_filtered=30.03. The optimizer didn't have any way to estimate which fraction of records will be left after it checks the condition that is attached to table orders (it's orders.o_totalprice > 200*1000). So, it used 100%. In reality, it is 30%. 30% is typically not selective enough to warrant adding new indexes. For joins with many tables, it might be worth to collect and use column statistics for columns in question, this may help the optimizer to pick a better query plan. Meaning of NULL in r_rows and r_filtered Let's modify the previous example slightly ANALYZE SELECT * FROM orders, customer WHERE customer.c_custkey=orders.o_custkey AND customer.c_acctbal 200*1000; +----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | r_rows | filtered | r_filtered | Extra | +----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+ | 1 | SIMPLE | customer | ALL | PRIMARY,... | NULL | NULL | NULL | 149095 | 150000 | 18.08 | 0.00 | Using where | | 1 | SIMPLE | orders | ref | i_o_custkey | i_o_custkey | 5 | customer.c_custkey | 7 | NULL | 100.00 | NULL | Using where | +----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+ Here, one can see that orders.r_rows=NULL and orders.r_filtered=NULL. This means that table orders was not scanned even once. Indeed, we can also see customer.r_filtered=0.00. This shows that a part of WHERE attached to table `customer` was never satisfied (or, satisfied in less than 0.01% of cases). ANALYZE FORMAT=JSON ANALYZE FORMAT=JSON produces JSON output. It produces much more information than tabular ANALYZE. Notes ANALYZE UPDATE or ANALYZE DELETE will actually make updates/deletes (ANALYZE SELECT will perform the select operation and then discard the resultset). PostgreSQL has a similar command, EXPLAIN ANALYZE. The EXPLAIN in the slow query log feature allows MariaDB to have ANALYZE output of slow queries printed into the slow query log (see MDEV-6388). URL: https://mariadb.com/kb/en/analyze-statement/https://mariadb.com/kb/en/analyze-statement/ l-Syntax ------ EXPLAIN tbl_name Or EXPLAIN [EXTENDED | PARTITIONS] {SELECT select_options | UPDATE update_options | DELETE delete_options} Description ----------- The EXPLAIN statement can be used either as a synonym for DESCRIBE or as a way to obtain information about how MariaDB executes a SELECT (as well as UPDATE and DELETE since MariaDB 10.0.5) statement: 'EXPLAIN tbl_name' is synonymous with 'DESCRIBE tbl_name' or 'SHOW COLUMNS FROM tbl_name'. When you precede a SELECT statement (or, since MariaDB 10.0.5, an UPDATE or a DELETE as well) with the keyword EXPLAIN, MariaDB displays information from the optimizer about the query execution plan. That is, MariaDB explains how it would process the SELECT, UPDATE or DELETE, including information about how tables are joined and in which order. EXPLAIN EXTENDED can be used to provide additional information. EXPLAIN PARTITIONS has been available since MySQL 5.1.5. It is useful only when examining queries involving partitioned tables. For details, see Partition pruning and selection. ANALYZE statement, which performs the query as well as producing EXPLAIN output, and provides actual as well as estimated statistics, has been available from MariaDB 10.1.0. Since MariaDB 10.0.5, it has been possible to have EXPLAIN output printed in the slow query log. See EXPLAIN in the Slow Query Log for details. Since MariaDB 10.0, SHOW EXPLAIN shows the output of a running statement. In some cases, its output can be closer to reality than EXPLAIN. Since MariaDB 10.1, the ANALYZE statement runs a statement and returns information about its execution plan. It also shows additional columns, to check how much the optimizer's estimation about filtering and found rows are close to reality. There is an online EXPLAIN Analyzer that you can use to share EXPLAIN and EXPLAIN EXTENDED output with others. EXPLAIN can acquire metadata locks in the same way that SELECT does, as it needs to know table metadata and, sometimes, data as well. The columns in EXPLAIN ... SELECT Column name | Description | id | Sequence number that shows in which order tables are joined. | select_type | What kind of SELECT the table comes from. | table | Alias name of table. Materialized temporary tables for sub queries are named | type | How rows are found from the table (join type). | possible_keys | keys in table that could be used to find rows in the table | key | The name of the key that is used to retrieve rows. NULL is no key was used. | key_len | How many bytes of the key that was used (shows if we are using only parts of the multi-column key). | ref | The reference that is used to as the key value. | rows | An estimate of how many rows we will find in the table for each key lookup. | Extra | Extra information about this join. | Here are descriptions of the values for some of the more complex columns in EXPLAIN ... SELECT: "select_type" column The select_type column can have the following values: Value | Description | DEPENDENT SUBQUERY | The SUBQUERY is DEPENDENT. | DEPENDENT UNION | The UNION is DEPENDENT. | DERIVED | The SELECT is DERIVED from the PRIMARY. | MATERIALIZED | The SUBQUERY is MATERIALIZED. | PRIMARY | The SELECT is a PRIMARY one. | SIMPLE | The SELECT is a SIMPLE one. | SUBQUERY | The SELECT is a SUBQUERY of the PRIMARY. | UNCACHEABLE SUBQUERY | The SUBQUERY is UNCACHEABLE. | UNCACHEABLE UNION | The UNION is UNCACHEABLE. | UNION | The SELECT is a UNION of the PRIMARY. | UNION RESULT | The result of the UNION. | "Type" column This column contains information on how the table is accessed. Value | Description | ALL | A full table scan is done for the table (all rows are read). This is bad if the table is large and the table is joined against a previous table! This happens when the optimizer could not find any usable index to access rows. | const | There is only one possibly matching row in the table. The row is read before the optimization phase and all columns in the table are treated as constants. | eq_ref | A unique index is used to find the rows. This is the best possible plan to find the row. | fulltext | A fulltext index is used to access the rows. | index_merge | A 'range' access is done for for several index and the found rows are merged. The key column shows which keys are used. | index_subquery | This is similar as ref, but used for sub queries that are transformed to key lookups. | index | A full scan over the used index. Better than ALL but still bad if index is large and the table is joined against a previous table. | range | The table will be accessed with a key over one or more value ranges. | ref_or_null | Like 'ref' but in addition another search for the 'null' value is done if the first value was not found. This happens usually with sub queries. | ref | A non unique index or prefix of an unique index is used to find the rows. Good if the prefix doesn't match many rows. | system | The table has 0 or 1 rows. | unique_subquery | This is similar as eq_ref, but used for sub queries that are transformed to key lookups | "Extra" column This column consists of one or more of the following values, separated by ';' Note that some of these values are detected after the optimization phase. The optimization phase can do the following changes to the WHERE clause: Add the expressions from the ON and USING clauses to the WHERE clause. Constant propagation: If there is column=constant, replace all column instances with this constant. Replace all columns from 'const' tables with their values. Remove the used key columns from the WHERE (as this will be tested as part of the key lookup). Remove impossible constant sub expressions. For example WHERE '(a=1 and a=2) OR b=1' becomes 'b=1'. Replace columns with other columns that has identical values: Example: WHERE a=b and a=c may be treated as 'WHERE a=b and a=c and b=c'. Add extra conditions to detect impossible row conditions earlier. This happens mainly with OUTER JOIN where we in some cases add detection of NULL values in the WHERE (Part of 'Not exists' optimization). This can cause an unexpected 'Using where' in the Extra column. For each table level we remove expressions that have already been tested when we read the previous row. Example: When joining tables t1 with t2 using the following WHERE 't1.a=1 and t1.a=t2.b', we don't have to test 't1.a=1' when checking rows in t2 as we already know that this expression is true. Value | Description | const row not found | The table was a system table (a table with should exactly one row), but no row was found. | Distinct | If distinct optimization (remove duplicates) was used. This is marked only for the last table in the SELECT. | Full scan on NULL key | The table is a part of the sub query and if the value that is used to match the sub query will be NULL, we will do a full table scan. | Impossible HAVING | The used HAVING clause is always false so the SELECT will return no rows. | Impossible WHERE noticed after reading const tables. | The used WHERE clause is always false so the SELECT will return no rows. This case was detected after we had read all 'const' tables and used the column values as constant in the WHERE clause. For example: WHERE const_column=5 and const_column had a value of 4. | Impossible WHERE | The used WHERE clause is always false so the SELECT will return no rows. For example: WHERE 1=2 | No matching min/max row | During early optimization of MIN()/MAX() values it was detected that no row could match the WHERE clause. The MIN()/MAX() function will return NULL. | no matching row in const table | The table was a const table (a table with only one possible matching row), but no row was found. | No tables used | The SELECT was a sub query that did not use any tables. For example a there was no FROM clause or a FROM DUAL clause. | Not exists | Stop searching after more row if we find one single matching row. This optimization is used with LEFT JOIN where one is explicitly searching for rows that doesn't eŀxists in the LEFT JOIN TABLE. Example: SELECT * FROM t1 LEFT JOIN t2 on (...) WHERE t2.not_null_column IS NULL. As t2.not_null_column can only be NULL if there was no matching row for on condition, we can stop searching if we find a single matching row. | Open_frm_only | For information_schema tables. Only the frm (table definition file was opened) was opened for each matching row. | Open_full_table | For information_schema tables. A full table open for each matching row is done to retrieve the requested information. (Slow) | Open_trigger_only | For information_schema tables. Only the trigger file definition was opened for each matching row. | Range checked for each record (index map: ...) | This only happens when there was no good default index to use but there may some index that could be used when we can treat all columns from previous table as constants. For each row combination the optimizer will decide which index to use (if any) to fetch a row from this table. This is not fast, but faster than a full table scan that is the only other choice. The index map is a bitmask that shows which index are considered for each row condition. | Scanned 0/1/all databases | For information_schema tables. Shows how many times we had to do a directory scan. | Select tables optimized away | All tables in the join was optimized away. This happens when we are only using COUNT(*), MIN() and MAX() functions in the SELECT and we where able to replace all of these with constants. | Skip_open_table | For information_schema tables. The queried table didn't need to be opened. | unique row not found | The table was detected to be a const table (a table with only one possible matching row) during the early optimization phase, but no row was found. | Using filesort | Filesort is needed to resolve the query. This means an extra phase where we first collect all columns to sort, sort them with a disk based merge sort and then use the sorted set to retrieve the rows in sorted order. If the column set is small, we store all the columns in the sort file to not have to go to the database to retrieve them again. | Using index | Only the index is used to retrieve the needed information from the table. There is no need to perform an extra seek to retrieve the actual record. | Using index condition | Like 'Using where' but the where condition is pushed down to the table engine for internal optimization at the index level. | Using index condition(BKA) | Like 'Using index condition' but in addition we use batch key access to retrieve rows. | Using index for group-by | The index is being used to resolve a GROUP BY or DISTINCT query. The rows are not read. This is very efficient if the table has a lot of identical index entries as duplicates are quickly jumped over. | Using intersect(...) | For index_merge joins. Shows which index are part of the intersect. | Using join buffer | We store previous row combinations in a row buffer to be able to match each row against all of the rows combinations in the join buffer at one go. | Using sort_union(...) | For index_merge joins. Shows which index are part of the union. | Using temporary | A temporary table is created to hold the result. This typically happens if you are using GROUP BY, DISTINCT or ORDER BY. | Using where | A WHERE expression (in additional to the possible key lookup) is used to check if the row should be accepted. If you don't have 'Using where' together with a join type of ALL, you are probably doing something wrong! | Using where with pushed condition | Like 'Using where' but the where condition is pushed down to the table engine for internal optimization at the row level. | Using buffer | The UPDATE statement will first buffer the rows, and then run the updates, rather than do updates on the fly. See Using Buffer UPDATE Algorithm for a detailed explanation. | EXPLAIN EXTENDED The EXTENDED keyword adds another column, filtered, to the output. This is a percentage estimate of the table rows that will be filtered by the condition. An EXPLAIN EXTENDED will always throw a warning, as it adds extra Message information to a subsequent SHOW WARNINGS statement. This includes what the SELECT query would look like after optimizing and rewriting rules are applied and how the optimizer qualifies columns and tables. Examples -------- As synonym for DESCRIBE or SHOW COLUMNS FROM: DESCRIBE city; +------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+----------+------+-----+---------+----------------+ | Id | int(11) | NO | PRI | NULL | auto_increment | | Name | char(35) | YES | | NULL | | | Country | char(3) | NO | UNI | | | | District | char(20) | YES | MUL | | | | Population | int(11) | YES | | NULL | | +------------+----------+------+-----+---------+----------------+ A simple set of examples to see how EXPLAIN can identify poor index usage: CREATE TABLE IF NOT EXISTS `employees_example` ( `id` int(11) NOT NULL AUTO_INCREMENT, `first_name` varchar(30) NOT NULL, `last_name` varchar(40) NOT NULL, `position` varchar(25) NOT NULL, `home_address` varchar(50) NOT NULL, `home_phone` varchar(12) NOT NULL, `employee_code` varchar(25) NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `employee_code` (`employee_code`), KEY `first_name` (`first_name`,`last_name`) ) ENGINE=Aria; INSERT INTO `employees_example` (`first_name`, `last_name`, `position`, `home_address`, `home_phone`, `employee_code`) VALUES ('Mustapha', 'Mond', 'Chief Executive Officer', '692 Promiscuous Plaza', '326-555-3492', 'MM1'), ('Henry', 'Foster', 'Store Manager', '314 Savage Circle', '326-555-3847', 'HF1'), ('Bernard', 'Marx', 'Cashier', '1240 Ambient Avenue', '326-555-8456', 'BM1'), ('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy Boulevard', '328-555-2349', 'LC1'), ('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky Lane', '326-555-6329', 'FC1'), ('Helmholtz', 'Watson', 'Janitor', '944 Soma Court', '329-555-2478', 'HW1'); SHOW INDEXES FROM employees_example; +-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | employees_example | 0 | PRIMARY | 1 | id | A | 7 | NULL | NULL | | BTREE | | | | employees_example | 0 | employee_code | 1 | employee_code | A | 7 | NULL | NULL | | BTREE | | | | employees_example | 1 | first_name | 1 | first_name | A | NULL | NULL | NULL | | BTREE | | | | employees_example | 1 | first_name | 2 | last_name | A | NULL | NULL | NULL | | BTREE | | | +-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ SELECT on a primary key: EXPLAIN SELECT * FROM employees_example WHERE id=1; +------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+ | 1 | SIMPLE | employees_example | const | PRIMARY | PRIMARY | 4 | const | 1 | | +------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+ The type is const, which means that only one possible result could be returned. Now, returning the same record but searching by their phone number: EXPLAIN SELECT * FROM employees_example WHERE home_phone='326-555-3492'; +------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +------+-------------+ KU b.EXPLAIN FORMAT=JSONStarting from version 10.1.2, MariaDB supports the EXPLAIN FORMAT=JSON syntax. Synopsis EXPLAIN FORMAT=JSON is a variant of EXPLAIN command that produces output in JSON form. The output always has one row which has only one column titled "JSON". The contents are a JSON representation of the query plan, formatted for readability: EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE col1=1\G *************************** 1. row *************************** EXPLAIN: { "query_block": { "select_id": 1, "table": { "table_name": "t1", "access_type": "ALL", "rows": 1000, "filtered": 100, "attached_condition": "(t1.col1 = 1)" } } } Output is different from MySQL The output of MariaDB's EXPLAIN FORMAT=JSON is different from EXPLAIN FORMAT=JSON in MySQL.The reasons for that are: MySQL's output has deficiencies. Some are listed here: EXPLAIN FORMAT=JSON in MySQL) The output of MySQL's EXPLAIN FORMAT=JSON is not defined. Even MySQL Workbench has trouble parsing it (see this blog post). MariaDB has query optimizations that MySQL does not have. Ergo, MariaDB generates query plans that MySQL does not generate. A (as yet incomplete) list of how MariaDB's output is different from MySQL can be found here: EXPLAIN FORMAT=JSON differences from MySQL. Output format TODO: MariaDB's output format description. URL: https://mariadb.com/kb/en/explain-format-json/https://mariadb.com/kb/en/explain-format-json/ c&ST_CONTAINSSyntax ------ ST_CONTAINS(g1,g2) Description ----------- Returns 1 or 0 to indicate whether a geometry g1 completely contains geometry g2. ST_CONTAINS() uses object shapes, while CONTAINS(), based on the original MySQL implementation, uses object bounding rectangles. ST_CONTAINS tests the opposite relationship to ST_WITHIN(). Examples -------- SET @g1 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'); SET @g2 = ST_GEOMFROMTEXT('POINT(174 149)'); SELECT ST_CONTAINS(@g1,@g2); +----------------------+ | ST_CONTAINS(@g1,@g2) | +----------------------+ | 1 | +----------------------+ SET @g2 = ST_GEOMFROMTEXT('POINT(175 151)'); SELECT ST_CONTAINS(@g1,@g2); +----------------------+ | ST_CONTAINS(@g1,@g2) | +----------------------+ | 0 | +----------------------+ URL: https://mariadb.com/kb/en/st-contains/https://mariadb.com/kb/en/st-contains/ %ST_CROSSESSyntax ------ ST_CROSSES(g1,g2) Description ----------- Returns 1 if geometry g1 spatially crosses geometry g2. Returns NULL if g1 is a Polygon or a MultiPolygon, or if g2 is a Point or a MultiPoint. Otherwise, returns 0. The term spatially crosses denotes a spatial relation between two given geometries that has the following properties: The two geometries intersect Their intersection results in a geometry that has a dimension that is one less than the maximum dimension of the two given geometries Their intersection is not equal to either of the two given geometries ST_CROSSES() uses object shapes, while CROSSES(), based on the original MySQL implementation, uses object bounding rectangles. Examples -------- SET @g1 = ST_GEOMFROMTEXT('LINESTRING(174 149, 176 151)'); SET @g2 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'); SELECT ST_CROSSES(@g1,@g2); +---------------------+ | ST_CROSSES(@g1,@g2) | +---------------------+ | 1 | +---------------------+ SET @g1 = ST_GEOMFROMTEXT('LINESTRING(176 149, 176 151)'); SELECT ST_CROSSES(@g1,@g2); +---------------------+ | ST_CROSSES(@g1,@g2) | +---------------------+ | 0 | +---------------------+ URL: https://mariadb.com/kb/en/st-crosses/https://mariadb.com/kb/en/st-crosses/ l&ST_DISJOINTSyntax ------ ST_DISJOINT(g1,g2) Description ----------- Returns 1 or 0 to indicate whether geometry g1 is spatially disjoint from (does not intersect with) geometry g2. ST_DISJOINT() uses object shapes, while DISJOINT(), based on the original MySQL implementation, uses object bounding rectangles. ST_DISJOINT() tests the opposite relationship to ST_INTERSECTS(). Examples -------- SET @g1 = ST_GEOMFROMTEXT('POINT(0 0)'); SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)'); SELECT ST_DISJOINT(@g1,@g2); +----------------------+ | ST_DISJOINT(@g1,@g2) | +----------------------+ | 1 | +----------------------+ SET @g2 = ST_GEOMFROMTEXT('LINESTRING(0 0, 0 2)'); SELECT ST_DISJOINT(@g1,@g2); +----------------------+ | ST_DISJOINT(@g1,@g2) | +----------------------+ | 0 | +----------------------+ URL: https://mariadb.com/kb/en/st_disjoint/https://mariadb.com/kb/en/st_disjoint/ ($ST_EQUALSSyntax ------ ST_EQUALS(g1,g2) Description ----------- Returns 1 or 0 to indicate whether geometry g1 is spatially equal to geometry g2. ST_EQUALS() uses object shapes, while EQUALS(), based on the original MySQL implementation, uses object bounding rectangles. Examples -------- SET @g1 = ST_GEOMFROMTEXT('LINESTRING(174 149, 176 151)'); SET @g2 = ST_GEOMFROMTEXT('LINESTRING(176 151, 174 149)'); SELECT ST_EQUALS(@g1,@g2); +--------------------+ | ST_EQUALS(@g1,@g2) | +--------------------+ | 1 | +--------------------+ SET @g1 = ST_GEOMFROMTEXT('POINT(0 2)'); SET @g1 = ST_GEOMFROMTEXT('POINT(2 0)'); SELECT ST_EQUALS(@g1,@g2); +--------------------+ | ST_EQUALS(@g1,@g2) | +--------------------+ | 0 | +--------------------+ URL: https://mariadb.com/kb/en/st-equals/https://mariadb.com/kb/en/st-equals/0c_ & S* h(ST_INTERSECTSSyntax ------ ST_INTERSECTS(g1,g2) Description ----------- Returns 1 or 0 to indicate whether geometry g1 spatially intersects geometry g2. ST_INTERSECTS() uses object shapes, while INTERSECTS(), based on the original MySQL implementation, uses object bounding rectangles. ST_INTERSECTS() tests the opposite relationship to ST_DISJOINT(). Examples -------- SET @g1 = ST_GEOMFROMTEXT('POINT(0 0)'); SET @g2 = ST_GEOMFROMTEXT('LINESTRING(0 0, 0 2)'); SELECT ST_INTERSECTS(@g1,@g2); +------------------------+ | ST_INTERSECTS(@g1,@g2) | +------------------------+ | 1 | +------------------------+ SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)'); SELECT ST_INTERSECTS(@g1,@g2); +------------------------+ | ST_INTERSECTS(@g1,@g2) | +------------------------+ | 0 | +------------------------+ URL: https://mariadb.com/kb/en/st-intersects/https://mariadb.com/kb/en/st-intersects/ %ST_TOUCHESSyntax ------ ST_TOUCHES(g1,g2) Description ----------- Returns 1 or 0 to indicate whether geometry g1 spatially touches geometry g2. Two geometries spatially touch if the interiors of the geometries do not intersect, but the boundary of one of the geometries intersects either the boundary or the interior of the other. ST_TOUCHES() uses object shapes, while TOUCHES(), based on the original MySQL implementation, uses object bounding rectangles. Examples -------- SET @g1 = ST_GEOMFROMTEXT('POINT(2 0)'); SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)'); SELECT ST_TOUCHES(@g1,@g2); +---------------------+ | ST_TOUCHES(@g1,@g2) | +---------------------+ | 1 | +---------------------+ SET @g1 = ST_GEOMFROMTEXT('POINT(2 1)'); SELECT ST_TOUCHES(@g1,@g2); +---------------------+ | ST_TOUCHES(@g1,@g2) | +---------------------+ | 0 | +---------------------+ URL: https://mariadb.com/kb/en/st-touches/https://mariadb.com/kb/en/st-touches/ @$ST_WITHINSyntax ------ ST_WITHIN(g1,g2) Description ----------- Returns 1 or 0 to indicate whether geometry g1 is spatially within geometry g2. This tests the opposite relationship as ST_CONTAINS(). ST_WITHIN() uses object shapes, while WITHIN(), based on the original MySQL implementation, uses object bounding rectangles. Examples -------- SET @g1 = ST_GEOMFROMTEXT('POINT(174 149)'); SET @g2 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'); SELECT ST_WITHIN(@g1,@g2); +--------------------+ | ST_WITHIN(@g1,@g2) | +--------------------+ | 1 | +--------------------+ SET @g1 = ST_GEOMFROMTEXT('POINT(176 151)'); SELECT ST_WITHIN(@g1,@g2); +--------------------+ | ST_WITHIN(@g1,@g2) | +--------------------+ | 0 | +--------------------+ URL: https://mariadb.com/kb/en/st-within/https://mariadb.com/kb/en/st-within/!WITHINSyntax ------ Within(g1,g2) Description ----------- Returns 1 or 0 to indicate whether g1 is spatially within g2. This tests the opposite relationship as Contains(). WITHIN() is based on the original MySQL implementation, and uses object bounding rectangles, while ST_WITHIN() uses object shapes. Examples -------- SET @g1 = GEOMFROMTEXT('POINT(174 149)'); SET @g2 = GEOMFROMTEXT('POINT(176 151)'); SET @g3 = GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'); SELECT within(@g1,@g3); +-----------------+ | within(@g1,@g3) | +-----------------+ | 1 | +-----------------+ SELECT within(@g2,@g3); +-----------------+ | within(@g2,@g3) | +-----------------+ | 0 | +-----------------+ URL: https://mariadb.com/kb/en/within/https://mariadb.com/kb/en/within/a "ADDDATESyntax ------ ADDDATE(date,INTERVAL expr unit), ADDDATE(expr,days) Description ----------- When invoked with the INTERVAL form of the second argument, ADDDATE() is a synonym for DATE_ADD(). The related function SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVAL unit argument, see the discussion for DATE_ADD(). When invoked with the days form of the second argument, MariaDB treats it as an integer number of days to be added to expr. Examples -------- SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY); +-----------------------------------------+ | DATE_ADD('2008-01-02', INTERVAL 31 DAY) | +-----------------------------------------+ | 2008-02-02 | +-----------------------------------------+ SELECT ADDDATE('2008-01-02', INTERVAL 31 DAY); +----------------------------------------+ | ADDDATE('2008-01-02', INTERVAL 31 DAY) | +----------------------------------------+ | 2008-02-02 | +----------------------------------------+ SELECT ADDDATE('2008-01-02', 31); +---------------------------+ | ADDDATE('2008-01-02', 31) | +---------------------------+ | 2008-02-02 | +---------------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT d, ADDDATE(d, 10) from t1; +---------------------+---------------------+ | d | ADDDATE(d, 10) | +---------------------+---------------------+ | 2007-01-30 21:31:07 | 2007-02-09 21:31:07 | | 1983-10-15 06:42:51 | 1983-10-25 06:42:51 | | 2011-04-21 12:34:56 | 2011-05-01 12:34:56 | | 2011-10-30 06:31:41 | 2011-11-09 06:31:41 | | 2011-01-30 14:03:25 | 2011-02-09 14:03:25 | | 2004-10-07 11:19:34 | 2004-10-17 11:19:34 | +---------------------+---------------------+ SELECT d, ADDDATE(d, INTERVAL 10 HOUR) from t1; +---------------------+------------------------------+ | d | ADDDATE(d, INTERVAL 10 HOUR) | +---------------------+------------------------------+ | 2007-01-30 21:31:07 | 2007-01-31 07:31:07 | | 1983-10-15 06:42:51 | 1983-10-15 16:42:51 | | 2011-04-21 12:34:56 | 2011-04-21 22:34:56 | | 2011-10-30 06:31:41 | 2011-10-30 16:31:41 | | 2011-01-30 14:03:25 | 2011-01-31 00:03:25 | | 2004-10-07 11:19:34 | 2004-10-07 21:19:34 | +---------------------+------------------------------+ URL: https://mariadb.com/kb/en/adddate/https://mariadb.com/kb/en/adddate/J  3{ ~Mn"ADDTIMESyntax ------ ADDTIME(expr1,expr2) Description ----------- ADDTIME() adds expr2 to expr1 and returns the result. expr1 is a time or datetime expression, and expr2 is a time expression. Examples -------- SELECT ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002'); +---------------------------------------------------------+ | ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002') | +---------------------------------------------------------+ | 2008-01-02 01:01:01.000001 | +---------------------------------------------------------+ SELECT ADDTIME('01:00:00.999999', '02:00:00.999998'); +-----------------------------------------------+ | ADDTIME('01:00:00.999999', '02:00:00.999998') | +-----------------------------------------------+ | 03:00:01.999997 | +-----------------------------------------------+ URL: https://mariadb.com/kb/en/addtime/https://mariadb.com/kb/en/addtime/ M%CONVERT_TZSyntax ------ CONVERT_TZ(dt,from_tz,to_tz) Description ----------- CONVERT_TZ() converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value. In order to use named time zones, such as GMT, MET or Africa/Johannesburg, the time_zone tables must be loaded (see mysql_tzinfo_to_sql). No conversion will take place if the value falls outside of the supported TIMESTAMP range ('1970-01-01 00:00:01' to '2038-01-19 05:14:07' UTC) when converted from from_tz to UTC. This function returns NULL if the arguments are invalid (or named time zones have not been loaded). See time zones for more information. Examples -------- SELECT CONVERT_TZ('2016-01-01 12:00:00','+00:00','+10:00'); +-----------------------------------------------------+ | CONVERT_TZ('2016-01-01 12:00:00','+00:00','+10:00') | +-----------------------------------------------------+ | 2016-01-01 22:00:00 | +-----------------------------------------------------+ Using named time zones (with the time zone tables loaded): SELECT CONVERT_TZ('2016-01-01 12:00:00','GMT','Africa/Johannesburg'); +---------------------------------------------------------------+ | CONVERT_TZ('2016-01-01 12:00:00','GMT','Africa/Johannesburg') | +---------------------------------------------------------------+ | 2016-01-01 14:00:00 | +---------------------------------------------------------------+ The value is out of the TIMESTAMP range, so no conversion takes place: SELECT CONVERT_TZ('1969-12-31 22:00:00','+00:00','+10:00'); +-----------------------------------------------------+ | CONVERT_TZ('1969-12-31 22:00:00','+00:00','+10:00') | +-----------------------------------------------------+ | 1969-12-31 22:00:00 | +-----------------------------------------------------+ URL: https://mariadb.com/kb/en/convert_tz/https://mariadb.com/kb/en/convert_tz/0#DATEDIFFSyntax ------ DATEDIFF(expr1,expr2) Description ----------- DATEDIFF() returns (expr1 – expr2) expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation. Examples -------- SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30'); +----------------------------------------------+ | DATEDIFF('2007-12-31 23:59:59','2007-12-30') | +----------------------------------------------+ | 1 | +----------------------------------------------+ SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31'); +----------------------------------------------+ | DATEDIFF('2010-11-30 23:59:59','2010-12-31') | +----------------------------------------------+ | -31 | +----------------------------------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT NOW(); +---------------------+ | NOW() | +---------------------+ | 2011-05-23 10:56:05 | +---------------------+ SELECT d, DATEDIFF(NOW(),d) FROM t1; +---------------------+-------------------+ | d | DATEDIFF(NOW(),d) | +---------------------+-------------------+ | 2007-01-30 21:31:07 | 1574 | | 1983-10-15 06:42:51 | 10082 | | 2011-04-21 12:34:56 | 32 | | 2011-10-30 06:31:41 | -160 | | 2011-01-30 14:03:25 | 113 | | 2004-10-07 11:19:34 | 2419 | +---------------------+-------------------+ URL: https://mariadb.com/kb/en/datediff/https://mariadb.com/kb/en/datediff/ #DATE_ADDSyntax ------ DATE_ADD(date,INTERVAL expr unit) Description ----------- Performs date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a "-" for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted. See Date and Time Units for a complete list of permitted units. See also DATE_SUB(). Examples -------- SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND; +-------------------------------------------+ | '2008-12-31 23:59:59' + INTERVAL 1 SECOND | +-------------------------------------------+ | 2009-01-01 00:00:00 | +-------------------------------------------+ SELECT INTERVAL 1 DAY + '2008-12-31'; +-------------------------------+ | INTERVAL 1 DAY + '2008-12-31' | +-------------------------------+ | 2009-01-01 | +-------------------------------+ SELECT '2005-01-01' - INTERVAL 1 SECOND; +----------------------------------+ | '2005-01-01' - INTERVAL 1 SECOND | +----------------------------------+ | 2004-12-31 23:59:59 | +----------------------------------+ SELECT DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND); +----------------------------------------------------+ | DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND) | +----------------------------------------------------+ | 2001-01-01 00:00:00 | +----------------------------------------------------+ SELECT DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY); +-------------------------------------------------+ | DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY) | +-------------------------------------------------+ | 2011-01-01 23:59:59 | +-------------------------------------------------+ SELECT DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND); +---------------------------------------------------------------+ | DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND) | +---------------------------------------------------------------+ | 2101-01-01 00:01:00 | +---------------------------------------------------------------+ SELECT DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10' DAY_HOUR); +------------------------------------------------------------+ | DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10' DAY_HOUR) | +------------------------------------------------------------+ | 1899-12-30 14:00:00 | +------------------------------------------------------------+ SELECT DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL '1.999999' SECOND_MICROSECOND); +--------------------------------------------------------------------------------+ | DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL '1.999999' SECOND_MICROSECOND) | +--------------------------------------------------------------------------------+ | 1993-01-01 00:00:01.000001 | +--------------------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/date_add/https://mariadb.com/kb/en/date_add/ ; i kn Z&DATE_FORMATSyntax ------ DATE_FORMAT(date, format[, locale]) Description ----------- Formats the date value according to the format string. The language used for the names is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales. The options that can be used by DATE_FORMAT(), as well as its inverse STR_TO_DATE() and the FROM_UNIXTIME() function, are: Option | Description | %a | Short weekday name in current locale (Variable lc_time_names). | %b | Short form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec. | %c | Month with 1 or 2 digits. | %D | Day with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...). | %d | Day with 2 digits. | %e | Day with 1 or 2 digits. | %f | Sub seconds 6 digits. | %H | Hour with 2 digits between 00-23. | %h | Hour with 2 digits between 01-12. | %I | Hour with 2 digits between 01-12. | %i | Minute with 2 digits. | %j | Day of the year (001-366) | %k | Hour with 1 digits between 0-23. | %l | Hour with 1 digits between 1-12. | %M | Full month name in current locale (Variable lc_time_names). | %m | Month with 2 digits. | %p | AM/PM according to current locale (Variable lc_time_names). | %r | Time in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'. | %S | Seconds with 2 digits. | %s | Seconds with 2 digits. | %T | Time in 24 hour format. Short for '%H:%i:%S'. | %U | Week number (00-53), when first day of the week is Sunday. | %u | Week number (00-53), when first day of the week is Monday. | %V | Week number (01-53), when first day of the week is Sunday. Used with %X. | %v | Week number (01-53), when first day of the week is Monday. Used with %x. | %W | Full weekday name in current locale (Variable lc_time_names). | %w | Day of the week. 0 = Sunday, 6 = Saturday. | %X | Year with 4 digits when first day of the week is Sunday. Used with %V. | %x | Year with 4 digits when first day of the week is Monday. Used with %v. | %Y | Year with 4 digits. | %y | Year with 2 digits. | %# | For str_to_date(), skip all numbers. | %. | For str_to_date(), skip all punctation characters. | %@ | For str_to_date(), skip all alpha characters. | %% | A literal % character. | To get a date in one of the standard formats, GET_FORMAT() can be used. Examples -------- SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y'); +------------------------------------------------+ | DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y') | +------------------------------------------------+ | Sunday October 2009 | +------------------------------------------------+ SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s'); +------------------------------------------------+ | DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s') | +------------------------------------------------+ | 22:23:00 | +------------------------------------------------+ SELECT DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m %b %j'); +------------------------------------------------------------+ | DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m %b %j') | +------------------------------------------------------------+ | 4th 00 Thu 04 10 Oct 277 | +------------------------------------------------------------+ SELECT DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T %S %w'); +------------------------------------------------------------+ | DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T %S %w') | +------------------------------------------------------------+ | 22 22 10 10:23:00 PM 22:23:00 00 6 | +------------------------------------------------------------+ SELECT DATE_FORMAT('1999-01-01', '%X %V'); +------------------------------------+ | DATE_FORMAT('1999-01-01', '%X %V') | +------------------------------------+ | 1998 52 | +------------------------------------+ SELECT DATE_FORMAT('2006-06-00', '%d'); +---------------------------------+ | DATE_FORMAT('2006-06-00', '%d') | +---------------------------------+ | 00 | +---------------------------------+ Optionally, the locale can be explicitly specified as the third DATE_FORMAT() argument. Doing so makes the function independent from the session settings, and the three argument version of DATE_FORMAT() can be used in virtual indexed and persistent generated-columns: SELECT DATE_FORMAT('2006-01-01', '%W', 'el_GR'); +------------------------------------------+ | DATE_FORMAT('2006-01-01', '%W', 'el_GR') | +------------------------------------------+ | Κυριακή | +------------------------------------------+ URL: https://mariadb.com/kb/en/date_format/https://mariadb.com/kb/en/date_format/#DATE_SUBSyntax ------ DATE_SUB(date,INTERVAL expr unit) Description ----------- Performs date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a "-" for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted. See Date and Time Units for a complete list of permitted units. See also DATE_ADD(). Examples -------- SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY); +-----------------------------------------+ | DATE_SUB('1998-01-02', INTERVAL 31 DAY) | +-----------------------------------------+ | 1997-12-02 | +-----------------------------------------+ SELECT DATE_SUB('2005-01-01 00:00:00', INTERVAL '1 1:1:1' DAY_SECOND); +----------------------------------------------------------------+ | DATE_SUB('2005-01-01 00:00:00', INTERVAL '1 1:1:1' DAY_SECOND) | +----------------------------------------------------------------+ | 2004-12-30 22:58:59 | +----------------------------------------------------------------+ URL: https://mariadb.com/kb/en/date_sub/https://mariadb.com/kb/en/date_sub/ xE "DAYNAMESyntax ------ DAYNAME(date) Description ----------- Returns the name of the weekday for date. The language used for the name is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales. Examples -------- SELECT DAYNAME('2007-02-03'); +-----------------------+ | DAYNAME('2007-02-03') | +-----------------------+ | Saturday | +-----------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT d, DAYNAME(d) FROM t1; +---------------------+------------+ | d | DAYNAME(d) | +---------------------+------------+ | 2007-01-30 21:31:07 | Tuesday | | 1983-10-15 06:42:51 | Saturday | | 2011-04-21 12:34:56 | Thursday | | 2011-10-30 06:31:41 | Sunday | | 2011-01-30 14:03:25 | Sunday | | 2004-10-07 11:19:34 | Thursday | +---------------------+------------+ Changing the locale: SET lc_time_names = 'fr_CA'; SELECT DAYNAME('2013-04-01'); +-----------------------+ | DAYNAME('2013-04-01') | +-----------------------+ | lundi | +-----------------------+ URL: https://mariadb.com/kb/en/dayname/https://mariadb.com/kb/en/dayname/ a%DAYOFMONTHSyntax ------ DAYOFMONTH(date) Description ----------- Returns the day of the month for date, in the range 1 to 31, or 0 for dates such as '0000-00-00' or '2008-00-00' which have a zero day part. DAY() is a synonym. Examples -------- SELECT DAYOFMONTH('2007-02-03'); +--------------------------+ | DAYOFMONTH('2007-02-03') | +--------------------------+ | 3 | +--------------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT d FROM t1 where DAYOFMONTH(d) = 30; +---------------------+ | d | +---------------------+ | 2007-01-30 21:31:07 | | 2011-10-30 06:31:41 | | 2011-01-30 14:03:25 | +---------------------+ URL: https://mariadb.com/kb/en/dayofmonth/https://mariadb.com/kb/en/dayofmonth/ "$DAYOFWEEKSyntax ------ DAYOFWEEK(date) Description ----------- Returns the day of the week index for the date (1 = Sunday, 2 = Monday, ..., 7 = Saturday). These index values correspond to the ODBC standard. This contrasts with WEEKDAY() which follows a different index numbering (0 = Monday, 1 = Tuesday, ... 6 = Sunday). Examples -------- SELECT DAYOFWEEK('2007-02-03'); +-------------------------+ | DAYOFWEEK('2007-02-03') | +-------------------------+ | 7 | +-------------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT d, DAYNAME(d), DAYOFWEEK(d), WEEKDAY(d) from t1; +---------------------+------------+--------------+------------+ | d | DAYNAME(d) | DAYOFWEEK(d) | WEEKDAY(d) | +---------------------+------------+--------------+------------+ | 2007-01-30 21:31:07 | Tuesday | 3 | 1 | | 1983-10-15 06:42:51 | Saturday | 7 | 5 | | 2011-04-21 12:34:56 | Thursday | 5 | 3 | | 2011-10-30 06:31:41 | Sunday | 1 | 6 | | 2011-01-30 14:03:25 | Sunday | 1 | 6 | | 2004-10-07 11:19:34 | Thursday | 5 | 3 | +---------------------+------------+--------------+------------+ URL: https://mariadb.com/kb/en/dayofweek/https://mariadb.com/kb/en/dayofweek/y"EXTRACTSyntax ------ EXTRACT(unit FROM date) Description ----------- The EXTRACT() function extracts the required unit from the date. See Date and Time Units for a complete list of permitted units. In MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR FROM ...) was changed to return a value from 0 to 23, adhering to the SQL standard. Until MariaDB 10.0.6 and MariaDB 5.5.34, and in all versions of MySQL at least as of MySQL 5.7, it could return a value > 23. HOUR() is not a standard function, so continues to adhere to the old behaviour inherited from MySQL. Examples -------- SELECT EXTRACT(YEAR FROM '2009-07-02'); +---------------------------------+ | EXTRACT(YEAR FROM '2009-07-02') | +---------------------------------+ | 2009 | +---------------------------------+ SELECT EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03'); +------------------------------------------------+ | EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03') | +------------------------------------------------+ | 200907 | +------------------------------------------------+ SELECT EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03'); +------------------------------------------------+ | EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03') | +------------------------------------------------+ | 20102 | +------------------------------------------------+ SELECT EXTRACT(MICROSECOND FROM '2003-01-02 10:30:00.000123'); +--------------------------------------------------------+ | EXTRACT(MICROSECOND FROM '2003-01-02 10:30:00.000123') | +--------------------------------------------------------+ | 123 | +--------------------------------------------------------+ From MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR FROM...) returns a value from 0 to 23, as per the SQL standard. HOUR is not a standard function, so continues to adhere to the old behaviour inherited from MySQL. SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00'); +-------------------------------+------------------+ | EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') | +-------------------------------+------------------+ | 2 | 26 | +-------------------------------+------------------+ URL: https://mariadb.com/kb/en/extract/https://mariadb.com/kb/en/extract/!]&  J h(FROM_UNIXTIMESyntax ------ FROM_UNIXTIME(unix_timestamp), FROM_UNIXTIME(unix_timestamp,format) Description ----------- Returns a representation of the unix_timestamp argument as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone. unix_timestamp is an internal timestamp value such as is produced by the UNIX_TIMESTAMP() function. If format is given, the result is formatted according to the format string, which is used the same way as listed in the entry for the DATE_FORMAT() function. Timestamps in MariaDB have a maximum value of 2147483647, equivalent to 2038-01-19 05:14:07. This is due to the underlying 32-bit limitation. Using the function on a timestamp beyond this will result in NULL being returned. Use DATETIME as a storage type if you require dates beyond this. The options that can be used by FROM_UNIXTIME(), as well as DATE_FORMAT() and STR_TO_DATE(), are: Option | Description | %a | Short weekday name in current locale (Variable lc_time_names). | %b | Short form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec. | %c | Month with 1 or 2 digits. | %D | Day with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...). | %d | Day with 2 digits. | %e | Day with 1 or 2 digits. | %f | Sub seconds 6 digits. | %H | Hour with 2 digits between 00-23. | %h | Hour with 2 digits between 01-12. | %I | Hour with 2 digits between 01-12. | %i | Minute with 2 digits. | %j | Day of the year (001-366) | %k | Hour with 1 digits between 0-23. | %l | Hour with 1 digits between 1-12. | %M | Full month name in current locale (Variable lc_time_names). | %m | Month with 2 digits. | %p | AM/PM according to current locale (Variable lc_time_names). | %r | Time in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'. | %S | Seconds with 2 digits. | %s | Seconds with 2 digits. | %T | Time in 24 hour format. Short for '%H:%i:%S'. | %U | Week number (00-53), when first day of the week is Sunday. | %u | Week number (00-53), when first day of the week is Monday. | %V | Week number (01-53), when first day of the week is Sunday. Used with %X. | %v | Week number (01-53), when first day of the week is Monday. Used with %x. | %W | Full weekday name in current locale (Variable lc_time_names). | %w | Day of the week. 0 = Sunday, 1 = Saturday. | %X | Year with 4 digits when first day of the week is Sunday. Used with %V. | %x | Year with 4 digits when first day of the week is Sunday. Used with %v. | %Y | Year with 4 digits. | %y | Year with 2 digits. | %# | For str_to_date(), skip all numbers. | %. | For str_to_date(), skip all punctation characters. | %@ | For str_to_date(), skip all alpha characters. | %% | A literal % character. | Performance Considerations If your session time zone is set to SYSTEM (the default), FROM_UNIXTIME() will call the OS function to convert the data using the system time zone. At least on Linux, the corresponding function (localtime_r) uses a global mutex inside glibc that can cause contention under high concurrent load. Set your time zone to a named time zone to avoid this issue. See mysql time zone tables for details on how to do this. Examples -------- SELECT FROM_UNIXTIME(1196440219); +---------------------------+ | FROM_UNIXTIME(1196440219) | +---------------------------+ | 2007-11-30 11:30:19 | +---------------------------+ SELECT FROM_UNIXTIME(1196440219) + 0; +-------------------------------+ | FROM_UNIXTIME(1196440219) + 0 | +-------------------------------+ | 20071130113019.000000 | +-------------------------------+ SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s %x'); +---------------------------------------------------------+ | FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s %x') | +---------------------------------------------------------+ | 2010 27th March 01:03:47 2010 | +---------------------------------------------------------+ URL: https://mariadb.com/kb/en/from_unixtime/https://mariadb.com/kb/en/from_unixtime/ v%GET_FORMATSyntax ------ GET_FORMAT({DATE|DATETIME|TIME}, {'EUR'|'USA'|'JIS'|'ISO'|'INTERNAL'}) Description ----------- Returns a format string. This function is useful in combination with the DATE_FORMAT() and the STR_TO_DATE() functions. Possible result formats are: Function Call | Result Format | GET_FORMAT(DATE,'EUR') | '%d.%m.%Y' | GET_FORMAT(DATE,'USA') | '%m.%d.%Y' | GET_FORMAT(DATE,'JIS') | '%Y-%m-%d' | GET_FORMAT(DATE,'ISO') | '%Y-%m-%d' | GET_FORMAT(DATE,'INTERNAL') | '%Y%m%d' | GET_FORMAT(DATETIME,'EUR') | '%Y-%m-%d %H.%i.%s' | GET_FORMAT(DATETIME,'USA') | '%Y-%m-%d %H.%i.%s' | GET_FORMAT(DATETIME,'JIS') | '%Y-%m-%d %H:%i:%s' | GET_FORMAT(DATETIME,'ISO') | '%Y-%m-%d %H:%i:%s' | GET_FORMAT(DATETIME,'INTERNAL') | '%Y%m%d%H%i%s' | GET_FORMAT(TIME,'EUR') | '%H.%i.%s' | GET_FORMAT(TIME,'USA') | '%h:%i:%s %p' | GET_FORMAT(TIME,'JIS') | '%H:%i:%s' | GET_FORMAT(TIME,'ISO') | '%H:%i:%s' | GET_FORMAT(TIME,'INTERNAL') | '%H%i%s' | Examples -------- Obtaining the string matching to the standard European date format: SELECT GET_FORMAT(DATE, 'EUR'); +-------------------------+ | GET_FORMAT(DATE, 'EUR') | +-------------------------+ | %d.%m.%Y | +-------------------------+ Using the same string to format a date: SELECT DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR')); +--------------------------------------------------+ | DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR')) | +--------------------------------------------------+ | 03.10.2003 | +--------------------------------------------------+ SELECT STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA')); +--------------------------------------------------+ | STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA')) | +--------------------------------------------------+ | 2003-10-31 | +--------------------------------------------------+ URL: https://mariadb.com/kb/en/get_format/https://mariadb.com/kb/en/get_format/ -kHOURSyntax ------ HOUR(time) Description ----------- Returns the hour for time. The range of the return value is 0 to 23 for time-of-day values. However, the range of TIME values actually is much larger, so HOUR can return values greater than 23. The return value is always positive, even if a negative TIME value is provided. Examples -------- SELECT HOUR('10:05:03'); +------------------+ | HOUR('10:05:03') | +------------------+ | 10 | +------------------+ SELECT HOUR('272:59:59'); +-------------------+ | HOUR('272:59:59') | +-------------------+ | 272 | +-------------------+ Difference between EXTRACT (HOUR FROM ...) (>= MariaDB 10.0.7 and MariaDB 5.5.35) and HOUR: SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00'); +-------------------------------+------------------+ | EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') | +-------------------------------+------------------+ | 2 | 26 | +-------------------------------+------------------+ URL: https://mariadb.com/kb/en/hour/https://mariadb.com/kb/en/hour/ #LAST_DAYSyntax ------ LAST_DAY(date) Description ----------- Takes a date or datetime value and returns the corresponding value for the last day of the month. Returns NULL if the argument is invalid. Examples -------- SELECT LAST_DAY('2003-02-05'); +------------------------+ | LAST_DAY('2003-02-05') | +------------------------+ | 2003-02-28 | +------------------------+ SELECT LAST_DAY('2004-02-05'); +------------------------+ | LAST_DAY('2004-02-05') | +------------------------+ | 2004-02-29 | +------------------------+ SELECT LAST_DAY('2004-01-01 01:01:01'); +---------------------------------+ | LAST_DAY('2004-01-01 01:01:01') | +---------------------------------+ | 2004-01-31 | +---------------------------------+ SELECT LAST_DAY('2003-03-32'); +------------------------+ | LAST_DAY('2003-03-32') | +------------------------+ | NULL | +------------------------+ 1 row in set, 1 warning (0.00 sec) Warning (Code 1292): Incorrect datetime value: '2003-03-32' URL: https://mariadb.com/kb/en/last_day/https://mariadb.com/kb/en/last_day/c#MAKEDATESyntax ------ MAKEDATE(year,dayofyear) Description ----------- Returns a date, given year and day-of-year values. dayofyear must be greater than 0 or the result is NULL. Examples -------- SELECT MAKEDATE(2011,31), MAKEDATE(2011,32); +-------------------+-------------------+ | MAKEDATE(2011,31) | MAKEDATE(2011,32) | +-------------------+-------------------+ | 2011-01-31 | 2011-02-01 | +-------------------+-------------------+ SELECT MAKEDATE(2011,365), MAKEDATE(2014,365); +--------------------+--------------------+ | MAKEDATE(2011,365) | MAKEDATE(2014,365) | +--------------------+--------------------+ | 2011-12-31 | 2014-12-31 | +--------------------+--------------------+ SELECT MAKEDATE(2011,0); +------------------+ | MAKEDATE(2011,0) | +------------------+ | NULL | +------------------+ URL: https://mariadb.com/kb/en/makedate/https://mariadb.com/kb/en/makedate/#MAKETIMESyntax ------ MAKETIME(hour,minute,second) Description ----------- Returns a time value calculated from the hour, minute, and second arguments. If minute or second are out of the range 0 to 60, NULL is returned. The hour can be in the range -838 to 838, outside of which the value is truncated with a warning. Examples -------- SELECT MAKETIME(13,57,33); +--------------------+ | MAKETIME(13,57,33) | +--------------------+ | 13:57:33 | +--------------------+ SELECT MAKETIME(-13,57,33); +---------------------+ | MAKETIME(-13,57,33) | +---------------------+ | -13:57:33 | +---------------------+ SELECT MAKETIME(13,67,33); +--------------------+ | MAKETIME(13,67,33) | +--------------------+ | NULL | +--------------------+ SELECT MAKETIME(-1000,57,33); +-----------------------+ | MAKETIME(-1000,57,33) | +-----------------------+ | -838:59:59 | +-----------------------+ 1 row in set, 1 warning (0.00 sec) SHOW WARNINGS; +---------+------+-----------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------+ | Warning | 1292 | Truncated incorrect time value: '-1000:57:33' | +---------+------+-----------------------------------------------+ URL: https://mariadb.com/kb/en/maketime/https://mariadb.com/kb/en/maketime/ &MICROSECONDSyntax ------ MICROSECOND(expr) Description ----------- Returns the microseconds from the time or datetime expression expr as a number in the range from 0 to 999999. If expr is a time with no microseconds, zero is returned, while if expr is a date with no time, zero with a warning is returned. Examples -------- SELECT MICROSECOND('12:00:00.123456'); +--------------------------------+ | MICROSECOND('12:00:00.123456') | +--------------------------------+ | 123456 | +--------------------------------+ SELECT MICROSECOND('2009-12-31 23:59:59.000010'); +-------------------------------------------+ | MICROSECOND('2009-12-31 23:59:59.000010') | +-------------------------------------------+ | 10 | +-------------------------------------------+ SELECT MICROSECOND('2013-08-07 12:13:14'); +------------------------------------+ | MICROSECOND('2013-08-07 12:13:14') | +------------------------------------+ | 0 | +------------------------------------+ SELECT MICROSECOND('2013-08-07'); +---------------------------+ | MICROSECOND('2013-08-07') | +---------------------------+ | 0 | +---------------------------+ 1 row in set, 1 warning (0.00 sec) SHOW WARNINGS; +---------+------+----------------------------------------------+ | Level | Code | Message | +---------+------+----------------------------------------------+ | Warning | 1292 | Truncated incorrect time value: '2013-08-07' | +---------+------+----------------------------------------------+ URL: https://mariadb.com/kb/en/microsecond/https://mariadb.com/kb/en/microsecond/R+ Jl*B h NOWSyntax ------ NOW([precision]) CURRENT_TIMESTAMP CURRENT_TIMESTAMP([precision]) LOCALTIME, LOCALTIME([precision]) LOCALTIMESTAMP LOCALTIMESTAMP([precision]) Description ----------- Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone. The optional precision determines the microsecond precision. See Microseconds in MariaDB. NOW() (or its synonyms) can be used as the default value for TIMESTAMP columns as well as, since MariaDB 10.0.1, DATETIME columns. Before MariaDB 10.0.1, it was only possible for a single TIMESTAMP column per table to contain the CURRENT_TIMESTAMP as its default. When displayed in the INFORMATION_SCHEMA.COLUMNS table, a default CURRENT TIMESTAMP is displayed as CURRENT_TIMESTAMP up until MariaDB 10.2.2, and as current_timestamp() from MariaDB 10.2.3, due to to MariaDB 10.2 accepting expressions in the DEFAULT clause. Examples -------- SELECT NOW(); +---------------------+ | NOW() | +---------------------+ | 2010-03-27 13:13:25 | +---------------------+ SELECT NOW() + 0; +-----------------------+ | NOW() + 0 | +-----------------------+ | 20100327131329.000000 | +-----------------------+ With precision: SELECT CURRENT_TIMESTAMP(2); +------------------------+ | CURRENT_TIMESTAMP(2) | +------------------------+ | 2018-07-10 09:47:26.24 | +------------------------+ Used as a default TIMESTAMP: CREATE TABLE t (createdTS TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP); From MariaDB 10.2.2: SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='test' AND COLUMN_NAME LIKE '%ts%'\G *************************** 1. row *************************** TABLE_CATALOG: def TABLE_SCHEMA: test TABLE_NAME: t COLUMN_NAME: ts ORDINAL_POSITION: 1 COLUMN_DEFAULT: current_timestamp() ... URL: https://mariadb.com/kb/en/now/https://mariadb.com/kb/en/now/ +%PERIOD_ADDSyntax ------ PERIOD_ADD(P,N) Description ----------- Adds N months to period P. P is in the format YYMM or YYYYMM, and is not a date value. If P contains a two-digit year, values from 00 to 69 are converted to from 2000 to 2069, while values from 70 are converted to 1970 upwards. Returns a value in the format YYYYMM. Examples -------- SELECT PERIOD_ADD(200801,2); +----------------------+ | PERIOD_ADD(200801,2) | +----------------------+ | 200803 | +----------------------+ SELECT PERIOD_ADD(6910,2); +--------------------+ | PERIOD_ADD(6910,2) | +--------------------+ | 206912 | +--------------------+ SELECT PERIOD_ADD(7010,2); +--------------------+ | PERIOD_ADD(7010,2) | +--------------------+ | 197012 | +--------------------+ URL: https://mariadb.com/kb/en/period_add/https://mariadb.com/kb/en/period_add/ w&PERIOD_DIFFSyntax ------ PERIOD_DIFF(P1,P2) Description ----------- Returns the number of months between periods P1 and P2. P1 and P2 can be in the format YYMM or YYYYMM, and are not date values. If P1 or P2 contains a two-digit year, values from 00 to 69 are converted to from 2000 to 2069, while values from 70 are converted to 1970 upwards. Examples -------- SELECT PERIOD_DIFF(200802,200703); +----------------------------+ | PERIOD_DIFF(200802,200703) | +----------------------------+ | 11 | +----------------------------+ SELECT PERIOD_DIFF(6902,6803); +------------------------+ | PERIOD_DIFF(6902,6803) | +------------------------+ | 11 | +------------------------+ SELECT PERIOD_DIFF(7002,6803); +------------------------+ | PERIOD_DIFF(7002,6803) | +------------------------+ | -1177 | +------------------------+ URL: https://mariadb.com/kb/en/period_diff/https://mariadb.com/kb/en/period_diff/ &SEC_TO_TIMESyntax ------ SEC_TO_TIME(seconds) Description ----------- Returns the seconds argument, converted to hours, minutes, and seconds, as a TIME value. The range of the result is constrained to that of the TIME data type. A warning occurs if the argument corresponds to a value outside that range. The time will be returned in the format hh:mm:ss, or hhmmss if used in a numeric calculation. Examples -------- SELECT SEC_TO_TIME(12414); +--------------------+ | SEC_TO_TIME(12414) | +--------------------+ | 03:26:54 | +--------------------+ SELECT SEC_TO_TIME(12414)+0; +----------------------+ | SEC_TO_TIME(12414)+0 | +----------------------+ | 32654 | +----------------------+ SELECT SEC_TO_TIME(9999999); +----------------------+ | SEC_TO_TIME(9999999) | +----------------------+ | 838:59:59 | +----------------------+ 1 row in set, 1 warning (0.00 sec) SHOW WARNINGS; +---------+------+-------------------------------------------+ | Level | Code | Message | +---------+------+-------------------------------------------+ | Warning | 1292 | Truncated incorrect time value: '9999999' | +---------+------+-------------------------------------------+ URL: https://mariadb.com/kb/en/sec_to_time/https://mariadb.com/kb/en/sec_to_time/ I h Nsn |&STR_TO_DATESyntax ------ STR_TO_DATE(str,format) Description ----------- This is the inverse of the DATE_FORMAT() function. It takes a string str and a format string format. STR_TO_DATE() returns a DATETIME value if the format string contains both date and time parts, or a DATE or TIME value if the string contains only date or time parts. The date, time, or datetime values contained in str should be given in the format indicated by format. If str contains an illegal date, time, or datetime value, STR_TO_DATE() returns NULL. An illegal value also produces a warning. The options that can be used by STR_TO_DATE(), as well as its inverse DATE_FORMAT() and the FROM_UNIXTIME() function, are: Option | Description | %a | Short weekday name in current locale (Variable lc_time_names). | %b | Short form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec. | %c | Month with 1 or 2 digits. | %D | Day with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...). | %d | Day with 2 digits. | %e | Day with 1 or 2 digits. | %f | Sub seconds 6 digits. | %H | Hour with 2 digits between 00-23. | %h | Hour with 2 digits between 01-12. | %I | Hour with 2 digits between 01-12. | %i | Minute with 2 digits. | %j | Day of the year (001-366) | %k | Hour with 1 digits between 0-23. | %l | Hour with 1 digits between 1-12. | %M | Full month name in current locale (Variable lc_time_names). | %m | Month with 2 digits. | %p | AM/PM according to current locale (Variable lc_time_names). | %r | Time in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'. | %S | Seconds with 2 digits. | %s | Seconds with 2 digits. | %T | Time in 24 hour format. Short for '%H:%i:%S'. | %U | Week number (00-53), when first day of the week is Sunday. | %u | Week number (00-53), when first day of the week is Monday. | %V | Week number (01-53), when first day of the week is Sunday. Used with %X. | %v | Week number (01-53), when first day of the week is Monday. Used with %x. | %W | Full weekday name in current locale (Variable lc_time_names). | %w | Day of the week. 0 = Sunday, 6 = Saturday. | %X | Year with 4 digits when first day of the week is Sunday. Used with %V. | %x | Year with 4 digits when first day of the week is Monday. Used with %v. | %Y | Year with 4 digits. | %y | Year with 2 digits. | %# | For str_to_date(), skip all numbers. | %. | For str_to_date(), skip all punctation characters. | %@ | For str_to_date(), skip all alpha characters. | %% | A literal % character. | Examples -------- SELECT STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e, %Y'); +---------------------------------------------------------+ | STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e, %Y') | +---------------------------------------------------------+ | 2014-06-02 | +---------------------------------------------------------+ SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W, %M %e, %Y'); +--------------------------------------------------------------+ | STR_TO_DATE('Wednesday23423, June 2, 2014', '%W, %M %e, %Y') | +--------------------------------------------------------------+ | NULL | +--------------------------------------------------------------+ 1 row in set, 1 warning (0.00 sec) SHOW WARNINGS; +---------+------+-----------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------+ | Warning | 1411 | Incorrect datetime value: 'Wednesday23423, June 2, 2014' for function str_to_date | +---------+------+-----------------------------------------------------------------------------------+ SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#, %M %e, %Y'); +----------------------------------------------------------------+ | STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#, %M %e, %Y') | +----------------------------------------------------------------+ | 2014-06-02 | +----------------------------------------------------------------+ URL: https://mariadb.com/kb/en/str_to_date/https://mariadb.com/kb/en/str_to_date/ "SUBDATESyntax ------ SUBDATE(date,INTERVAL expr unit), SUBDATE(expr,days) Description ----------- When invoked with the INTERVAL form of the second argument, SUBDATE() is a synonym for DATE_SUB(). See Date and Time Units for a complete list of permitted units. The second form allows the use of an integer value for days. In such cases, it is interpreted as the number of days to be subtracted from the date or datetime expression expr. Examples -------- SELECT DATE_SUB('2008-01-02', INTERVAL 31 DAY); +-----------------------------------------+ | DATE_SUB('2008-01-02', INTERVAL 31 DAY) | +-----------------------------------------+ | 2007-12-02 | +-----------------------------------------+ SELECT SUBDATE('2008-01-02', INTERVAL 31 DAY); +----------------------------------------+ | SUBDATE('2008-01-02', INTERVAL 31 DAY) | +----------------------------------------+ | 2007-12-02 | +----------------------------------------+ SELECT SUBDATE('2008-01-02 12:00:00', 31); +------------------------------------+ | SUBDATE('2008-01-02 12:00:00', 31) | +------------------------------------+ | 2007-12-02 12:00:00 | +------------------------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT d, SUBDATE(d, 10) from t1; +---------------------+---------------------+ | d | SUBDATE(d, 10) | +---------------------+---------------------+ | 2007-01-30 21:31:07 | 2007-01-20 21:31:07 | | 1983-10-15 06:42:51 | 1983-10-05 06:42:51 | | 2011-04-21 12:34:56 | 2011-04-11 12:34:56 | | 2011-10-30 06:31:41 | 2011-10-20 06:31:41 | | 2011-01-30 14:03:25 | 2011-01-20 14:03:25 | | 2004-10-07 11:19:34 | 2004-09-27 11:19:34 | +---------------------+---------------------+ SELECT d, SUBDATE(d, INTERVAL 10 MINUTE) from t1; +---------------------+--------------------------------+ | d | SUBDATE(d, INTERVAL 10 MINUTE) | +---------------------+--------------------------------+ | 2007-01-30 21:31:07 | 2007-01-30 21:21:07 | | 1983-10-15 06:42:51 | 1983-10-15 06:32:51 | | 2011-04-21 12:34:56 | 2011-04-21 12:24:56 | | 2011-10-30 06:31:41 | 2011-10-30 06:21:41 | | 2011-01-30 14:03:25 | 2011-01-30 13:53:25 | | 2004-10-07 11:19:34 | 2004-10-07 11:09:34 | +---------------------+--------------------------------+ URL: https://mariadb.com/kb/en/subdate/https://mariadb.com/kb/en/subdate/ FA# "SUBTIMESyntax ------ SUBTIME(expr1,expr2) Description ----------- SUBTIME() returns expr1 - expr2 expressed as a value in the same format as expr1. expr1 is a time or datetime expression, and expr2 is a time expression. Examples -------- SELECT SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002'); +--------------------------------------------------------+ | SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002') | +--------------------------------------------------------+ | 2007-12-30 22:58:58.999997 | +--------------------------------------------------------+ SELECT SUBTIME('01:00:00.999999', '02:00:00.999998'); +-----------------------------------------------+ | SUBTIME('01:00:00.999999', '02:00:00.999998') | +-----------------------------------------------+ | -00:59:59.999999 | +-----------------------------------------------+ URL: https://mariadb.com/kb/en/subtime/https://mariadb.com/kb/en/subtime/# "SYSDATESyntax ------ SYSDATE([precision]) Description ----------- Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The optional precision determines the microsecond precision. See Microseconds in MariaDB. SYSDATE() returns the time at which it executes. This differs from the behavior for NOW(), which returns a constant time that indicates the time at which the statement began to execute. (Within a stored routine or trigger, NOW() returns the time at which the routine or triggering statement began to execute.) In addition, changing the timestamp system variable with a SET timestamp statement affects the value returned by NOW() but not by SYSDATE(). This means that timestamp settings in the binary log have no effect on invocations of SYSDATE(). Because SYSDATE() can return different values even within the same statement, and is not affected by SET TIMESTAMP, it is non-deterministic and therefore unsafe for replication if statement-based binary logging is used. If that is a problem, you can use row-based logging, or start the server with the mysqld option --sysdate-is-now to cause SYSDATE() to be an alias for NOW(). The non-deterministic nature of SYSDATE() also means that indexes cannot be used for evaluating expressions that refer to it, and that statements using the SYSDATE() function are unsafe for statement-based replication. Examples -------- Difference between NOW() and SYSDATE(): SELECT NOW(), SLEEP(2), NOW(); +---------------------+----------+---------------------+ | NOW() | SLEEP(2) | NOW() | +---------------------+----------+---------------------+ | 2010-03-27 13:23:40 | 0 | 2010-03-27 13:23:40 | +---------------------+----------+---------------------+ SELECT SYSDATE(), SLEEP(2), SYSDATE(); +---------------------+----------+---------------------+ | SYSDATE() | SLEEP(2) | SYSDATE() | +---------------------+----------+---------------------+ | 2010-03-27 13:23:52 | 0 | 2010-03-27 13:23:54 | +---------------------+----------+---------------------+ With precision: SELECT SYSDATE(4); +--------------------------+ | SYSDATE(4) | +--------------------------+ | 2018-07-10 10:17:13.1689 | +--------------------------+ URL: https://mariadb.com/kb/en/sysdate/https://mariadb.com/kb/en/sysdate/#TIMEDIFFSyntax ------ TIMEDIFF(expr1,expr2) Description ----------- TIMEDIFF() returns expr1 - expr2 expressed as a time value. expr1 and expr2 are time or date-and-time expressions, but both must be of the same type. Examples -------- SELECT TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001'); +---------------------------------------------------------------+ | TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001') | +---------------------------------------------------------------+ | -00:00:00.000001 | +---------------------------------------------------------------+ SELECT TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30 01:01:01.000002'); +----------------------------------------------------------------------+ | TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30 01:01:01.000002') | +----------------------------------------------------------------------+ | 46:58:57.999999 | +----------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/timediff/https://mariadb.com/kb/en/timediff/O-TIMESTAMP FUNCTIONSyntax ------ TIMESTAMP(expr), TIMESTAMP(expr1,expr2) Description ----------- With a single argument, this function returns the date or datetime expression expr as a datetime value. With two arguments, it adds the time expression expr2 to the date or datetime expression expr1 and returns the result as a datetime value. Examples -------- SELECT TIMESTAMP('2003-12-31'); +-------------------------+ | TIMESTAMP('2003-12-31') | +-------------------------+ | 2003-12-31 00:00:00 | +-------------------------+ SELECT TIMESTAMP('2003-12-31 12:00:00','6:30:00'); +--------------------------------------------+ | TIMESTAMP('2003-12-31 12:00:00','6:30:00') | +--------------------------------------------+ | 2003-12-31 18:30:00 | +--------------------------------------------+ URL: https://mariadb.com/kb/en/timestamp-function/https://mariadb.com/kb/en/timestamp-function/k# HZ ~r  ='TIMESTAMPADDSyntax ------ TIMESTAMPADD(unit,interval,datetime_expr) Description ----------- Adds the integer expression interval to the date or datetime expression datetime_expr. The unit for interval is given by the unit argument, which should be one of the following values: MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR. The unit value may be specified using one of keywords as shown, or with a prefix of SQL_TSI_. For example, DAY and SQL_TSI_DAY both are legal. Before MariaDB 5.5, FRAC_SECOND was permitted as a synonym for MICROSECOND. Examples -------- SELECT TIMESTAMPADD(MINUTE,1,'2003-01-02'); +-------------------------------------+ | TIMESTAMPADD(MINUTE,1,'2003-01-02') | +-------------------------------------+ | 2003-01-02 00:01:00 | +-------------------------------------+ SELECT TIMESTAMPADD(WEEK,1,'2003-01-02'); +-----------------------------------+ | TIMESTAMPADD(WEEK,1,'2003-01-02') | +-----------------------------------+ | 2003-01-09 | +-----------------------------------+ URL: https://mariadb.com/kb/en/timestampadd/https://mariadb.com/kb/en/timestampadd/ (TIMESTAMPDIFFSyntax ------ TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2) Description ----------- Returns datetime_expr2 - datetime_expr1, where datetime_expr1 and datetime_expr2 are date or datetime expressions. One expression may be a date and the other a datetime; a date value is treated as a datetime having the time part '00:00:00' where necessary. The unit for the result (an integer) is given by the unit argument. The legal values for unit are the same as those listed in the description of the TIMESTAMPADD() function, i.e MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR. TIMESTAMPDIFF can also be used to calculate age. Examples -------- SELECT TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01'); +------------------------------------------------+ | TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01') | +------------------------------------------------+ | 3 | +------------------------------------------------+ SELECT TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01'); +-----------------------------------------------+ | TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01') | +-----------------------------------------------+ | -1 | +-----------------------------------------------+ SELECT TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55'); +----------------------------------------------------------+ | TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55') | +----------------------------------------------------------+ | 128885 | +----------------------------------------------------------+ Calculating age: SELECT CURDATE(); +------------+ | CURDATE() | +------------+ | 2019-05-27 | +------------+ SELECT TIMESTAMPDIFF(YEAR, '1971-06-06', CURDATE()) AS age; +------+ | age | +------+ | 47 | +------+ SELECT TIMESTAMPDIFF(YEAR, '1971-05-06', CURDATE()) AS age; +------+ | age | +------+ | 48 | +------+ Age as of 2014-08-02: SELECT name, date_of_birth, TIMESTAMPDIFF(YEAR,date_of_birth,'2014-08-02') AS age FROM student_details; +---------+---------------+------+ | name | date_of_birth | age | +---------+---------------+------+ | Chun | 1993-12-31 | 20 | | Esben | 1946-01-01 | 68 | | Kaolin | 1996-07-16 | 18 | | Tatiana | 1988-04-13 | 26 | +---------+---------------+------+ URL: https://mariadb.com/kb/en/timestampdiff/https://mariadb.com/kb/en/timestampdiff/"TO_DAYSSyntax ------ TO_DAYS(date) Description ----------- Given a date date, returns the number of days since the start of the current calendar (0000-00-00). The function is not designed for use with dates before the advent of the Gregorian calendar in October 1582. Results will not be reliable since it doesn't account for the lost days when the calendar changed from the Julian calendar. This is the converse of the FROM_DAYS() function. Examples -------- SELECT TO_DAYS('2007-10-07'); +-----------------------+ | TO_DAYS('2007-10-07') | +-----------------------+ | 733321 | +-----------------------+ SELECT TO_DAYS('0000-01-01'); +-----------------------+ | TO_DAYS('0000-01-01') | +-----------------------+ | 1 | +-----------------------+ SELECT TO_DAYS(950501); +-----------------+ | TO_DAYS(950501) | +-----------------+ | 728779 | +-----------------+ URL: https://mariadb.com/kb/en/to_days/https://mariadb.com/kb/en/to_days/ #%TO_SECONDSSyntax ------ TO_SECONDS(expr) Description ----------- Returns the number of seconds from year 0 till expr, or NULL if expr is not a valid date or datetime. Examples -------- SELECT TO_SECONDS('2013-06-13'); +--------------------------+ | TO_SECONDS('2013-06-13') | +--------------------------+ | 63538300800 | +--------------------------+ SELECT TO_SECONDS('2013-06-13 21:45:13'); +-----------------------------------+ | TO_SECONDS('2013-06-13 21:45:13') | +-----------------------------------+ | 63538379113 | +-----------------------------------+ SELECT TO_SECONDS(NOW()); +-------------------+ | TO_SECONDS(NOW()) | +-------------------+ | 63543530875 | +-------------------+ SELECT TO_SECONDS(20130513); +----------------------+ | TO_SECONDS(20130513) | +----------------------+ | 63535622400 | +----------------------+ 1 row in set (0.00 sec) SELECT TO_SECONDS(130513); +--------------------+ | TO_SECONDS(130513) | +--------------------+ | 63535622400 | +--------------------+ URL: https://mariadb.com/kb/en/to_seconds/https://mariadb.com/kb/en/to_seconds/` 7 ~L1i )UNIX_TIMESTAMPSyntax ------ UNIX_TIMESTAMP() UNIX_TIMESTAMP(date) Description ----------- If called with no argument, returns a Unix timestamp (seconds since '1970-01-01 00:00:00' UTC) as an unsigned integer. If UNIX_TIMESTAMP() is called with a date argument, it returns the value of the argument as seconds since '1970-01-01 00:00:00' UTC. date may be a DATE string, a DATETIME string, a TIMESTAMP, or a number in the format YYMMDD or YYYYMMDD. The server interprets date as a value in the current time zone and converts it to an internal value in UTC. Clients can set their time zone as described in time zones. The inverse function of UNIX_TIMESTAMP() is FROM_UNIXTIME() UNIX_TIMESTAMP() supports microseconds. Timestamps in MariaDB have a maximum value of 2147483647, equivalent to 2038-01-19 05:14:07. This is due to the underlying 32-bit limitation. Using the function on a date beyond this will result in NULL being returned. Use DATETIME as a storage type if you require dates beyond this. Error Handling Returns NULL for wrong arguments to UNIX_TIMESTAMP(). In MySQL and MariaDB before 5.3 wrong arguments to UNIX_TIMESTAMP() returned 0. Compatibility As you can see in the examples above, UNIX_TIMESTAMP(constant-date-string) returns a timestamp with 6 decimals while MariaDB 5.2 and before returns it without decimals. This can cause a problem if you are using UNIX_TIMESTAMP() as a partitioning function. You can fix this by using FLOOR(UNIX_TIMESTAMP(..)) or changing the date string to a date number, like 20080101000000. Examples -------- SELECT UNIX_TIMESTAMP(); +------------------+ | UNIX_TIMESTAMP() | +------------------+ | 1269711082 | +------------------+ SELECT UNIX_TIMESTAMP('2007-11-30 10:30:19'); +---------------------------------------+ | UNIX_TIMESTAMP('2007-11-30 10:30:19') | +---------------------------------------+ | 1196436619.000000 | +---------------------------------------+ SELECT UNIX_TIMESTAMP("2007-11-30 10:30:19.123456"); +----------------------------------------------+ | unix_timestamp("2007-11-30 10:30:19.123456") | +----------------------------------------------+ | 1196411419.123456 | +----------------------------------------------+ SELECT FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30 10:30:19')); +------------------------------------------------------+ | FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30 10:30:19')) | +------------------------------------------------------+ | 2007-11-30 10:30:19.000000 | +------------------------------------------------------+ SELECT FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30 10:30:19'))); +-------------------------------------------------------------+ | FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30 10:30:19'))) | +-------------------------------------------------------------+ | 2007-11-30 10:30:19 | +-------------------------------------------------------------+ URL: https://mariadb.com/kb/en/unix_timestamp/https://mariadb.com/kb/en/unix_timestamp/  y(UTC_TIMESTAMPSyntax ------ UTC_TIMESTAMP UTC_TIMESTAMP([precision]) Description ----------- Returns the current UTC date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The optional precision determines the microsecond precision. See Microseconds in MariaDB. Examples -------- SELECT UTC_TIMESTAMP(), UTC_TIMESTAMP() + 0; +---------------------+-----------------------+ | UTC_TIMESTAMP() | UTC_TIMESTAMP() + 0 | +---------------------+-----------------------+ | 2010-03-27 17:33:16 | 20100327173316.000000 | +---------------------+-----------------------+ With precision: SELECT UTC_TIMESTAMP(4); +--------------------------+ | UTC_TIMESTAMP(4) | +--------------------------+ | 2018-07-10 07:51:09.1019 | +--------------------------+ URL: https://mariadb.com/kb/en/utc_timestamp/https://mariadb.com/kb/en/utc_timestamp/ WEEKSyntax ------ WEEK(date[,mode]) Description ----------- This function returns the week number for date. The two-argument form of WEEK() allows you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range from 0 to 53 or from 1 to 53. If the mode argument is omitted, the value of the default_week_format system variable is used. Modes Mode | 1st day of week | Range | Week 1 is the 1st week with | 0 | Sunday | 0-53 | a Sunday in this year | 1 | Monday | 0-53 | more than 3 days this year | 2 | Sunday | 1-53 | a Sunday in this year | 3 | Monday | 1-53 | more than 3 days this year | 4 | Sunday | 0-53 | more than 3 days this year | 5 | Monday | 0-53 | a Monday in this year | 6 | Sunday | 1-53 | more than 3 days this year | 7 | Monday | 1-53 | a Monday in this year | Examples -------- SELECT WEEK('2008-02-20'); +--------------------+ | WEEK('2008-02-20') | +--------------------+ | 7 | +--------------------+ SELECT WEEK('2008-02-20',0); +----------------------+ | WEEK('2008-02-20',0) | +----------------------+ | 7 | +----------------------+ SELECT WEEK('2008-02-20',1); +----------------------+ | WEEK('2008-02-20',1) | +----------------------+ | 8 | +----------------------+ SELECT WEEK('2008-12-31',0); +----------------------+ | WEEK('2008-12-31',0) | +----------------------+ | 52 | +----------------------+ SELECT WEEK('2008-12-31',1); +----------------------+ | WEEK('2008-12-31',1) | +----------------------+ | 53 | +----------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT d, WEEK(d,0), WEEK(d,1) from t1; +---------------------+-----------+-----------+ | d | WEEK(d,0) | WEEK(d,1) | +---------------------+-----------+-----------+ | 2007-01-30 21:31:07 | 4 | 5 | | 1983-10-15 06:42:51 | 41 | 41 | | 2011-04-21 12:34:56 | 16 | 16 | | 2011-10-30 06:31:41 | 44 | 43 | | 2011-01-30 14:03:25 | 5 | 4 | | 2004-10-07 11:19:34 | 40 | 41 | +---------------------+-----------+-----------+ URL: https://mariadb.com/kb/en/week/https://mariadb.com/kb/en/week/v  -  "WEEKDAYSyntax ------ WEEKDAY(date) Description ----------- Returns the weekday index for date (0 = Monday, 1 = Tuesday, ... 6 = Sunday). This contrasts with DAYOFWEEK() which follows the ODBC standard (1 = Sunday, 2 = Monday, ..., 7 = Saturday). Examples -------- SELECT WEEKDAY('2008-02-03 22:23:00'); +--------------------------------+ | WEEKDAY('2008-02-03 22:23:00') | +--------------------------------+ | 6 | +--------------------------------+ SELECT WEEKDAY('2007-11-06'); +-----------------------+ | WEEKDAY('2007-11-06') | +-----------------------+ | 1 | +-----------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT d FROM t1 where WEEKDAY(d) = 6; +---------------------+ | d | +---------------------+ | 2011-10-30 06:31:41 | | 2011-01-30 14:03:25 | +---------------------+ URL: https://mariadb.com/kb/en/weekday/https://mariadb.com/kb/en/weekday/ >%WEEKOFYEARSyntax ------ WEEKOFYEAR(date) Description ----------- Returns the calendar week of the date as a number in the range from 1 to 53. WEEKOFYEAR() is a compatibility function that is equivalent to WEEK(date,3). Examples -------- SELECT WEEKOFYEAR('2008-02-20'); +--------------------------+ | WEEKOFYEAR('2008-02-20') | +--------------------------+ | 8 | +--------------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); select * from t1; +---------------------+ | d | +---------------------+ | 2007-01-30 21:31:07 | | 1983-10-15 06:42:51 | | 2011-04-21 12:34:56 | | 2011-10-30 06:31:41 | | 2011-01-30 14:03:25 | | 2004-10-07 11:19:34 | +---------------------+ SELECT d, WEEKOFYEAR(d), WEEK(d,3) from t1; +---------------------+---------------+-----------+ | d | WEEKOFYEAR(d) | WEEK(d,3) | +---------------------+---------------+-----------+ | 2007-01-30 21:31:07 | 5 | 5 | | 1983-10-15 06:42:51 | 41 | 41 | | 2011-04-21 12:34:56 | 16 | 16 | | 2011-10-30 06:31:41 | 43 | 43 | | 2011-01-30 14:03:25 | 4 | 4 | | 2004-10-07 11:19:34 | 41 | 41 | +---------------------+---------------+-----------+ URL: https://mariadb.com/kb/en/weekofyear/https://mariadb.com/kb/en/weekofyear/YEARSyntax ------ YEAR(date) Description ----------- Returns the year for the given date, in the range 1000 to 9999, or 0 for the "zero" date. Examples -------- CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT * FROM t1; +---------------------+ | d | +---------------------+ | 2007-01-30 21:31:07 | | 1983-10-15 06:42:51 | | 2011-04-21 12:34:56 | | 2011-10-30 06:31:41 | | 2011-01-30 14:03:25 | | 2004-10-07 11:19:34 | +---------------------+ SELECT * FROM t1 WHERE YEAR(d) = 2011; +---------------------+ | d | +---------------------+ | 2011-04-21 12:34:56 | | 2011-10-30 06:31:41 | | 2011-01-30 14:03:25 | +---------------------+ SELECT YEAR('1987-01-01'); +--------------------+ | YEAR('1987-01-01') | +--------------------+ | 1987 | +--------------------+ URL: https://mariadb.com/kb/en/year/https://mariadb.com/kb/en/year/#YEARWEEKSyntax ------ YEARWEEK(date), YEARWEEK(date,mode) Description ----------- Returns year and week for a date. The mode argument works exactly like the mode argument to WEEK(). The year in the result may be different from the year in the date argument for the first and the last week of the year. Examples -------- SELECT YEARWEEK('1987-01-01'); +------------------------+ | YEARWEEK('1987-01-01') | +------------------------+ | 198652 | +------------------------+ CREATE TABLE t1 (d DATETIME); INSERT INTO t1 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT * FROM t1; +---------------------+ | d | +---------------------+ | 2007-01-30 21:31:07 | | 1983-10-15 06:42:51 | | 2011-04-21 12:34:56 | | 2011-10-30 06:31:41 | | 2011-01-30 14:03:25 | | 2004-10-07 11:19:34 | +---------------------+ 6 rows in set (0.02 sec) SELECT YEARWEEK(d) FROM t1 WHERE YEAR(d) = 2011; +-------------+ | YEARWEEK(d) | +-------------+ | 201116 | | 201144 | | 201105 | +-------------+ 3 rows in set (0.03 sec) URL: https://mariadb.com/kb/en/yearweek/https://mariadb.com/kb/en/yearweek/7 Well-Known Binary (WKB) FormatWKB stands for Well-Known Binary, a format for representing geographical and geometrical data. WKB uses 1-byte unsigned integers, 4-byte unsigned integers, and 8-byte double-precision numbers. The first byte indicates the byte order. 00 for big endian, or 01 for little endian. The next 4 bytes indicate the geometry type. Values from 1 to 7 indicate whether the type is Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection respectively. The 8-byte floats represent the co-ordinates. Take the following example, a sequence of 21 bytes each represented by two hex digits: 000000000140000000000000004010000000000000 It's big endian 000000000140000000000000004010000000000000 It's a POINT 000000000140000000000000004010000000000000 The X co-ordinate is 2.0 000000000140000000000000004010000000000000 The Y-co-ordinate is 4.0 000000000140000000000000004010000000000000 URL: https://mariadb.com/kb/en/well-known-binary-wkb-format/https://mariadb.com/kb/en/well-known-binary-wkb-format/I  I{ ='2  ' MPolyFromWKBSyntax ------ MPolyFromWKB(wkb[,srid]) MultiPolygonFromWKB(wkb[,srid]) Description ----------- Constructs a MULTIPOLYGON value using its WKB representation and SRID. MPolyFromWKB() and MultiPolygonFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(MPointFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')); SELECT ST_AsText(MPolyFromWKB(@g)); +---------------------------------------------------------------------------------------------------------------+ | ST_AsText(MPolyFromWKB(@g)) | +---------------------------------------------------------------------------------------------------------------+ | MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18))) | +---------------------------------------------------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/mpolyfromwkb/https://mariadb.com/kb/en/mpolyfromwkb/%- ST_GeomCollFromWKBSyntax ------ ST_GeomCollFromWKB(wkb[,srid]) ST_GeometryCollectionFromWKB(wkb[,srid]) GeomCollFromWKB(wkb[,srid]) GeometryCollectionFromWKB(wkb[,srid]) Description ----------- Constructs a GEOMETRYCOLLECTION value using its WKB representation and SRID. ST_GeomCollFromWKB(), ST_GeometryCollectionFromWKB(), GeomCollFromWKB() and GeometryCollectionFromWKB() are synonyms. Examples -------- SET @g = ST_AsBinary(ST_GeomFromText('GEOMETRYCOLLECTION(POLYGON((5 5,10 5,10 10,5 5)),POINT(10 10))')); SELECT ST_AsText(ST_GeomCollFromWKB(@g)); +----------------------------------------------------------------+ | ST_AsText(ST_GeomCollFromWKB(@g)) | +----------------------------------------------------------------+ | GEOMETRYCOLLECTION(POLYGON((5 5,10 5,10 10,5 5)),POINT(10 10)) | +----------------------------------------------------------------+ URL: https://mariadb.com/kb/en/st_geomcollfromwkb/https://mariadb.com/kb/en/st_geomcollfromwkb/9 ~&$ST_BOUNDARYThe ST_BOUNDARY function was introduced in MariaDB 10.1.2 Syntax ------ ST_BOUNDARY(g) BOUNDARY(g) Description ----------- Returns a geometry that is the closure of the combinatorial boundary of the geometry value g. BOUNDARY() is a synonym. Examples -------- SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3 3,0 0, -3 3)'))); +----------------------------------------------------------------------+ | ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3 3,0 0, -3 3)'))) | +----------------------------------------------------------------------+ | MULTIPOINT(3 3,-3 3) | +----------------------------------------------------------------------+ SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3 3,0 0, -3 3, 3 3))'))); +--------------------------------------------------------------------------+ | ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3 3,0 0, -3 3, 3 3))'))) | +--------------------------------------------------------------------------+ | LINESTRING(3 3,0 0,-3 3,3 3) | +--------------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/st_boundary/https://mariadb.com/kb/en/st_boundary/; &$ST_ENVELOPESyntax ------ ST_ENVELOPE(g) ENVELOPE(g) Description ----------- Returns the Minimum Bounding Rectangle (MBR) for the geometry value g. The result is returned as a Polygon value. The polygon is defined by the corner points of the bounding box: POLYGON((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY)) ST_ENVELOPE() and ENVELOPE() are synonyms. Examples -------- SELECT AsText(ST_ENVELOPE(GeomFromText('LineString(1 1,4 4)'))); +----------------------------------------------------------+ | AsText(ST_ENVELOPE(GeomFromText('LineString(1 1,4 4)'))) | +----------------------------------------------------------+ | POLYGON((1 1,4 1,4 4,1 4,1 1)) | +----------------------------------------------------------+ URL: https://mariadb.com/kb/en/st_envelope/https://mariadb.com/kb/en/st_envelope/> Y&$ST_ISCLOSEDSyntax ------ ST_IsClosed(g) IsClosed(g) Description ----------- Returns 1 if a given LINESTRING's start and end points are the same, or 0 if they are not the same. Before MariaDB 10.1.5, returns NULL if not given a LINESTRING. After MariaDB 10.1.5, returns -1. ST_IsClosed() and IsClosed() are synonyms. Examples -------- SET @ls = 'LineString(0 0, 0 4, 4 4, 0 0)'; SELECT ST_ISCLOSED(GEOMFROMTEXT(@ls)); +--------------------------------+ | ST_ISCLOSED(GEOMFROMTEXT(@ls)) | +--------------------------------+ | 1 | +--------------------------------+ SET @ls = 'LineString(0 0, 0 4, 4 4, 0 1)'; SELECT ST_ISCLOSED(GEOMFROMTEXT(@ls)); +--------------------------------+ | ST_ISCLOSED(GEOMFROMTEXT(@ls)) | +--------------------------------+ | 0 | +--------------------------------+ URL: https://mariadb.com/kb/en/st_isclosed/https://mariadb.com/kb/en/st_isclosed/ S( 5D)Gu*%BINARY OperatorSyntax ------ BINARY Description ----------- The BINARY operator casts the string following it to a binary string. This is an easy way to force a column comparison to be done byte by byte rather than character by character. This causes the comparison to be case sensitive even if the column isn't defined as BINARY or BLOB. BINARY also causes trailing spaces to be significant. Examples -------- SELECT 'a' = 'A'; +-----------+ | 'a' = 'A' | +-----------+ | 1 | +-----------+ SELECT BINARY 'a' = 'A'; +------------------+ | BINARY 'a' = 'A' | +------------------+ | 0 | +------------------+ SELECT 'a' = 'a '; +------------+ | 'a' = 'a ' | +------------+ | 1 | +------------+ SELECT BINARY 'a' = 'a '; +-------------------+ | BINARY 'a' = 'a ' | +-------------------+ | 0 | +-------------------+ URL: https://mariadb.com/kb/en/binary-operator/https://mariadb.com/kb/en/binary-operator/Iv%CASTSyntax ------ CAST(expr AS type) Description ----------- The CAST() function takes a value of one type and produces a value of another type, similar to the CONVERT() function. For more information, see the description of CONVERT(). The main difference between the CAST() and CONVERT() is that CONVERT(expr,type) is ODBC syntax while CAST(expr as type) and CONVERT(... USING ...) are SQL92 syntax. In MariaDB 10.4 and later, you can use the CAST() function with the INTERVAL keyword. Until MariaDB 5.5.31, X'HHHH', the standard SQL syntax for binary string literals, erroneously worked in the same way as 0xHHHH. In 5.5.31 it was intentionally changed to behave as a string in all contexts (and never as a number). This introduces an incompatibility with previous versions of MariaDB, and all versions of MySQL (see the example below). Examples -------- Simple casts: SELECT CAST("abc" AS BINARY); SELECT CAST("1" AS UNSIGNED INTEGER); SELECT CAST(123 AS CHAR CHARACTER SET utf8) Note that when one casts to CHAR without specifying the character set, the collation_connection character set collation will be used. When used with CHAR CHARACTER SET, the default collation for that character set will be used. SELECT COLLATION(CAST(123 AS CHAR)); +------------------------------+ | COLLATION(CAST(123 AS CHAR)) | +------------------------------+ | latin1_swedish_ci | +------------------------------+ SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8)); +-------------------------------------------------+ | COLLATION(CAST(123 AS CHAR CHARACTER SET utf8)) | +-------------------------------------------------+ | utf8_general_ci | +-------------------------------------------------+ If you also want to change the collation, you have to use the COLLATE operator: SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8) COLLATE utf8_unicode_ci); +-------------------------------------------------------------------------+ | COLLATION(CAST(123 AS CHAR CHARACTER SET utf8) COLLATE utf8_unicode_ci) | +-------------------------------------------------------------------------+ | utf8_unicode_ci | +-------------------------------------------------------------------------+ Using CAST() to order an ENUM field as a CHAR rather than the internal numerical value: CREATE TABLE enum_list (enum_field enum('c','a','b')); INSERT INTO enum_list (enum_field) VALUES('c'),('a'),('c'),('b'); SELECT * FROM enum_list ORDER BY enum_field; +------------+ | enum_field | +------------+ | c | | c | | a | | b | +------------+ SELECT * FROM enum_list ORDER BY CAST(enum_field AS CHAR); +------------+ | enum_field | +------------+ | a | | b | | c | | c | +------------+ From MariaDB 5.5.31, the following will trigger warnings, since x'aa' and 'X'aa' no longer behave as a number. Previously, and in all versions of MySQL, no warnings are triggered since they did erroneously behave as a number: SELECT CAST(0xAA AS UNSIGNED), CAST(x'aa' AS UNSIGNED), CAST(X'aa' AS UNSIGNED); +------------------------+-------------------------+-------------------------+ | CAST(0xAA AS UNSIGNED) | CAST(x'aa' AS UNSIGNED) | CAST(X'aa' AS UNSIGNED) | +------------------------+-------------------------+-------------------------+ | 170 | 0 | 0 | +------------------------+-------------------------+-------------------------+ 1 row in set, 2 warnings (0.00 sec) Warning (Code 1292): Truncated incorrect INTEGER value: '\xAA' Warning (Code 1292): Truncated incorrect INTEGER value: '\xAA' Casting to intervals: SELECT CAST(2019-01-04 INTERVAL AS DAY_SECOND(2)) AS "Cast"; +-------------+ | Cast | +-------------+ | 00:20:17.00 | +-------------+ URL: https://mariadb.com/kb/en/cast/https://mariadb.com/kb/en/cast/J H(%CHAR FunctionSyntax ------ CHAR(N,... [USING charset_name]) Description ----------- CHAR() interprets each argument as an INT and returns a string consisting of the characters given by the code values of those integers. NULL values are skipped. By default, CHAR() returns a binary string. To produce a string in a given character set, use the optional USING clause: SELECT CHARSET(CHAR(0x65)), CHARSET(CHAR(0x65 USING utf8)); +---------------------+--------------------------------+ | CHARSET(CHAR(0x65)) | CHARSET(CHAR(0x65 USING utf8)) | +---------------------+--------------------------------+ | binary | utf8 | +---------------------+--------------------------------+ If USING is given and the result string is illegal for the given character set, a warning is issued. Also, if strict SQL mode is enabled, the result from CHAR() becomes NULL. Examples -------- SELECT CHAR(77,97,114,'105',97,'68',66); +----------------------------------+ | CHAR(77,97,114,'105',97,'68',66) | +----------------------------------+ | MariaDB | +----------------------------------+ SELECT CHAR(77,77.3,'77.3'); +----------------------+ | CHAR(77,77.3,'77.3') | +----------------------+ | MMM | +----------------------+ 1 row in set, 1 warning (0.00 sec) Warning (Code 1292): Truncated incorrect INTEGER value: '77.3' URL: https://mariadb.com/kb/en/char-function/https://mariadb.com/kb/en/char-function/o  L &%CHAR_LENGTHSyntax ------ CHAR_LENGTH(str) Description ----------- Returns the length of the given string argument, measured in characters. A multi-byte character counts as a single character. This means that for a string containing five two-byte characters, LENGTH() (or OCTET_LENGTH() in Oracle mode) returns 10, whereas CHAR_LENGTH() returns 5. If the argument is NULL, it returns NULL. If the argument is not a string value, it is converted into a string. It is synonymous with the CHARACTER_LENGTH() function. Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits. Examples -------- SELECT CHAR_LENGTH('MariaDB'); +------------------------+ | CHAR_LENGTH('MariaDB') | +------------------------+ | 7 | +------------------------+ SELECT CHAR_LENGTH('π'); +-------------------+ | CHAR_LENGTH('π') | +-------------------+ | 1 | +-------------------+ URL: https://mariadb.com/kb/en/char_length/https://mariadb.com/kb/en/char_length/M%CHRThe CHR() function was introduced in MariaDB 10.3.1 to provide Oracle compatibility Syntax ------ CHR(N) Description ----------- CHR() interprets each argument N as an integer and returns a VARCHAR(1) string consisting of the character given by the code values of the integer. The character set and collation of the string are set according to the values of the character_set_database and collation_database system variables. CHR() is similar to the CHAR() function, but only accepts a single argument. CHR() is available in all sql_modes. Examples -------- SELECT CHR(67); +---------+ | CHR(67) | +---------+ | C | +---------+ SELECT CHR('67'); +-----------+ | CHR('67') | +-----------+ | C | +-----------+ SELECT CHR('C'); +----------+ | CHR('C') | +----------+ | | +----------+ 1 row in set, 1 warning (0.000 sec) SHOW WARNINGS; +---------+------+----------------------------------------+ | Level | Code | Message | +---------+------+----------------------------------------+ | Warning | 1292 | Truncated incorrect INTEGER value: 'C' | +---------+------+----------------------------------------+ URL: https://mariadb.com/kb/en/chr/https://mariadb.com/kb/en/chr/N!%CONCATSyntax ------ CONCAT(str1,str2,...) Description ----------- Returns the string that results from concatenating the arguments. May have one or more arguments. If all arguments are non-binary strings, the result is a non-binary string. If the arguments include any binary strings, the result is a binary string. A numeric argument is converted to its equivalent binary string form; if you want to avoid that, you can use an explicit type cast, as in this example: SELECT CONCAT(CAST(int_col AS CHAR), char_col); CONCAT() returns NULL if any argument is NULL. A NULL parameter hides all information contained in other parameters from the result. Sometimes this is not desirable; to avoid this, you can: Use the CONCAT_WS() function with an empty separator, because that function is NULL-safe. Use IFNULL() to turn NULLs into empty strings. Oracle Mode In Oracle mode from MariaDB 10.3, CONCAT ignores NULL. Examples -------- SELECT CONCAT('Ma', 'ria', 'DB'); +---------------------------+ | CONCAT('Ma', 'ria', 'DB') | +---------------------------+ | MariaDB | +---------------------------+ SELECT CONCAT('Ma', 'ria', NULL, 'DB'); +---------------------------------+ | CONCAT('Ma', 'ria', NULL, 'DB') | +---------------------------------+ | NULL | +---------------------------------+ SELECT CONCAT(42.0); +--------------+ | CONCAT(42.0) | +--------------+ | 42.0 | +--------------+ Using IFNULL() to handle NULLs: SELECT CONCAT('The value of @v is: ', IFNULL(@v, '')); +------------------------------------------------+ | CONCAT('The value of @v is: ', IFNULL(@v, '')) | +------------------------------------------------+ | The value of @v is: | +------------------------------------------------+ In Oracle mode, from MariaDB 10.3: SELECT CONCAT('Ma', 'ria', NULL, 'DB'); +---------------------------------+ | CONCAT('Ma', 'ria', NULL, 'DB') | +---------------------------------+ | MariaDB | +---------------------------------+ URL: https://mariadb.com/kb/en/concat/https://mariadb.com/kb/en/concat/O $%CONCAT_WSSyntax ------ CONCAT_WS(separator,str1,str2,...) Description ----------- CONCAT_WS() stands for Concatenate With Separator and is a special form of CONCAT(). The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments. If the separator is NULL, the result is NULL; all other NULL values are skipped. This makes CONCAT_WS() suitable when you want to concatenate some values and avoid losing all information if one of them is NULL. Examples -------- SELECT CONCAT_WS(',','First name','Second name','Last Name'); +-------------------------------------------------------+ | CONCAT_WS(',','First name','Second name','Last Name') | +-------------------------------------------------------+ | First name,Second name,Last Name | +-------------------------------------------------------+ SELECT CONCAT_WS('-','Floor',NULL,'Room'); +------------------------------------+ | CONCAT_WS('-','Floor',NULL,'Room') | +------------------------------------+ | Floor-Room | +------------------------------------+ In some cases, remember to include a space in the separator string: SET @a = 'gnu', @b = 'penguin', @c = 'sea lion'; Query OK, 0 rows affected (0.00 sec) SELECT CONCAT_WS(', ', @a, @b, @c); +-----------------------------+ | CONCAT_WS(', ', @a, @b, @c) | +-----------------------------+ | gnu, penguin, sea lion | +-----------------------------+ Using CONCAT_WS() to handle NULLs: SET @a = 'a', @b = NULL, @c = 'c'; SELECT CONCAT_WS('', @a, @b, @c); +---------------------------+ | CONCAT_WS('', @a, @b, @c) | +---------------------------+ | ac | +---------------------------+ URL: https://mariadb.com/kb/en/concat_ws/https://mariadb.com/kb/en/concat_ws/( P D@3 PA"%CONVERTSyntax ------ CONVERT(expr,type), CONVERT(expr USING transcoding_name) Description ----------- The CONVERT() and CAST() functions take a value of one type and produce a value of another type. The type can be one of the following values: BINARY CHAR DATE DATETIME DECIMAL[(M[,D])] DOUBLE FLOAT — From MariaDB 10.4.5 INTEGER Short for SIGNED INTEGER SIGNED [INTEGER] TIME UNSIGNED [INTEGER] Note that in MariaDB, INT and INTEGER are the same thing. BINARY produces a string with the BINARY data type. If the optional length is given, BINARY(N) causes the cast to use no more than N bytes of the argument. Values shorter than the given number in bytes are padded with 0x00 bytes to make them equal the length value. CHAR(N) causes the cast to use no more than the number of characters given in the argument. The main difference between the CAST() and CONVERT() is that CONVERT(expr,type) is ODBC syntax while CAST(expr as type) and CONVERT(... USING ...) are SQL92 syntax. CONVERT() with USING is used to convert data between different character sets. In MariaDB, transcoding names are the same as the corresponding character set names. For example, this statement converts the string 'abc' in the default character set to the corresponding string in the utf8 character set: SELECT CONVERT('abc' USING utf8); Examples -------- SELECT enum_col FROM tbl_name ORDER BY CAST(enum_col AS CHAR); Converting a BINARY to string to permit the LOWER function to work: SET @x = 'AardVark'; SET @x = BINARY 'AardVark'; SELECT LOWER(@x), LOWER(CONVERT (@x USING latin1)); +-----------+----------------------------------+ | LOWER(@x) | LOWER(CONVERT (@x USING latin1)) | +-----------+----------------------------------+ | AardVark | aardvark | +-----------+----------------------------------+ URL: https://mariadb.com/kb/en/convert/https://mariadb.com/kb/en/convert/Q%ELTSyntax ------ ELT(N, str1[, str2, str3,...]) Description ----------- Takes a numeric argument and a series of string arguments. Returns the string that corresponds to the given numeric position. For instance, it returns str1 if N is 1, str2 if N is 2, and so on. If the numeric argument is a FLOAT, MariaDB rounds it to the nearest INTEGER. If the numeric argument is less than 1, greater than the total number of arguments, or not a number, ELT() returns NULL. It must have at least two arguments. It is complementary to the FIELD() function. Examples -------- SELECT ELT(1, 'ej', 'Heja', 'hej', 'foo'); +------------------------------------+ | ELT(1, 'ej', 'Heja', 'hej', 'foo') | +------------------------------------+ | ej | +------------------------------------+ SELECT ELT(4, 'ej', 'Heja', 'hej', 'foo'); +------------------------------------+ | ELT(4, 'ej', 'Heja', 'hej', 'foo') | +------------------------------------+ | foo | +------------------------------------+ URL: https://mariadb.com/kb/en/elt/https://mariadb.com/kb/en/elt/R ,%%EXPORT_SETSyntax ------ EXPORT_SET(bits, on, off[, separator[, number_of_bits]]) Description ----------- Takes a minimum of three arguments. Returns a string where each bit in the given bits argument is returned, with the string values given for on and off. Bits are examined from right to left, (from low-order to high-order bits). Strings are added to the result from left to right, separated by a separator string (defaults as ','). You can optionally limit the number of bits the EXPORT_SET() function examines using the number_of_bits option. If any of the arguments are set as NULL, the function returns NULL. Examples -------- SELECT EXPORT_SET(5,'Y','N',',',4); +-----------------------------+ | EXPORT_SET(5,'Y','N',',',4) | +-----------------------------+ | Y,N,Y,N | +-----------------------------+ SELECT EXPORT_SET(6,'1','0',',',10); +------------------------------+ | EXPORT_SET(6,'1','0',',',10) | +------------------------------+ | 0,1,1,0,0,0,0,0,0,0 | +------------------------------+ URL: https://mariadb.com/kb/en/export_set/https://mariadb.com/kb/en/export_set/T %FIELDSyntax ------ FIELD(pattern, str1[,str2,...]) Description ----------- Returns the index position of the string or number matching the given pattern. Returns 0 in the event that none of the arguments match the pattern. Raises an Error 1582 if not given at least two arguments. When all arguments given to the FIELD() function are strings, they are treated as case-insensitive. When all the arguments are numbers, they are treated as numbers. Otherwise, they are treated as doubles. If the given pattern occurs more than once, the FIELD() function only returns the index of the first instance. If the given pattern is NULL, the function returns 0, as a NULL pattern always fails to match. This function is complementary to the ELT() function. Examples -------- SELECT FIELD('ej', 'Hej', 'ej', 'Heja', 'hej', 'foo') AS 'Field Results'; +---------------+ | Field Results | +---------------+ | 2 | +---------------+ SELECT FIELD('fo', 'Hej', 'ej', 'Heja', 'hej', 'foo') AS 'Field Results'; +---------------+ | Field Results | +---------------+ | 0 | +---------------+ SELECT FIELD(1, 2, 3, 4, 5, 1) AS 'Field Results'; +---------------+ | Field Results | +---------------+ | 5 | +---------------+ SELECT FIELD(NULL, 2, 3) AS 'Field Results'; +---------------+ | Field Results | +---------------+ | 0 | +---------------+ SELECT FIELD('fail') AS 'Field Results'; Error 1582 (42000): Incorrect parameter count in call to native function 'field' URL: https://mariadb.com/kb/en/field/https://mariadb.com/kb/en/field/+, i> x.` S '%EXTRACTVALUESyntax ------ EXTRACTVALUE(xml_frag, xpath_expr) Description ----------- The EXTRACTVALUE() function takes two string arguments: a fragment of XML markup and an XPath expression, (also known as a locator). It returns the text (That is, CDDATA), of the first text node which is a child of the element or elements matching the XPath expression. In cases where a valid XPath expression does not match any text nodes in a valid XML fragment, (including the implicit /text() expression), the EXTRACTVALUE() function returns an empty string. Invalid Arguments When either the XML fragment or the XPath expression is NULL, the EXTRACTVALUE() function returns NULL. When the XML fragment is invalid, it raises a warning Code 1525: Warning (Code 1525): Incorrect XML value: 'parse error at line 1 pos 11: unexpected END-OF-INPUT' When the XPath value is invalid, it generates an Error 1105: ERROR 1105 (HY000): XPATH syntax error: ')' Explicit text() Expressions This function is the equivalent of performing a match using the XPath expression after appending /text(). In other words: SELECT EXTRACTVALUE('example', '/cases/case') AS 'Base Example', EXTRACTVALUE('example', '/cases/case/text()') AS 'text() Example'; +--------------+----------------+ | Base Example | text() Example | +--------------+----------------+ | example | example | +--------------+----------------+ Count Matches When EXTRACTVALUE() returns multiple matches, it returns the content of the first child text node of each matching element, in the matched order, as a single, space-delimited string. By design, the EXTRACTVALUE() function makes no distinction between a match on an empty element and no match at all. If you need to determine whether no matching element was found in the XML fragment or if an element was found that contained no child text nodes, use the XPath count() function. For instance, when looking for a value that exists, but contains no child text nodes, you would get a count of the number of matching instances: SELECT EXTRACTVALUE('', '/cases/case') AS 'Empty Example', EXTRACTVALUE('', '/cases/case/count()') AS 'count() Example'; +---------------+-----------------+ | Empty Example | count() Example | +---------------+-----------------+ | | 1 | +---------------+-----------------+ Alternatively, when looking for a value that doesn't exist, count() returns 0. SELECT EXTRACTVALUE('', '/cases/person') AS 'No Match Example', EXTRACTVALUE('', '/cases/person/count()') AS 'count() Example'; +------------------+-----------------+ | No Match Example | count() Example | +------------------+-----------------+ | | 0| +------------------+-----------------+ Matches Important: The EXTRACTVALUE() function only returns CDDATA. It does not return tags that the element might contain or the text that these child elements contain. SELECT EXTRACTVALUE('Personx@example.com', '/cases') AS Case; +--------+ | Case | +--------+ | Person | +--------+ Note, in the above example, while the XPath expression matches to the parent instance, it does not return the contained tag or its content. Examples -------- SELECT ExtractValue('cccddd', '/a') AS val1, ExtractValue('cccddd', '/a/b') AS val2, ExtractValue('cccddd', '//b') AS val3, ExtractValue('cccddd', '/b') AS val4, ExtractValue('cccdddeee', '//b') AS val5; +------+------+------+------+---------+ | val1 | val2 | val3 | val4 | val5 | +------+------+------+------+---------+ | ccc | ddd | ddd | | ddd eee | +------+------+------+------+---------+ URL: https://mariadb.com/kb/en/extractvalue/https://mariadb.com/kb/en/extractvalue/U Z&%FIND_IN_SETSyntax ------ FIND_IN_SET(pattern, strlist) Description ----------- Returns the index position where the given pattern occurs in a string list. The first argument is the pattern you want to search for. The second argument is a string containing comma-separated variables. If the second argument is of the SET data-type, the function is optimized to use bit arithmetic. If the pattern does not occur in the string list or if the string list is an empty string, the function returns 0. If either argument is NULL, the function returns NULL. The function does not return the correct result if the pattern contains a comma (",") character. Examples -------- SELECT FIND_IN_SET('b','a,b,c,d') AS "Found Results"; +---------------+ | Found Results | +---------------+ | 2 | +---------------+ URL: https://mariadb.com/kb/en/find_in_set/https://mariadb.com/kb/en/find_in_set/VU!%FORMATSyntax ------ FORMAT(num, decimal_position[, locale]) Description ----------- Formats the given number for display as a string, adding separators to appropriate position and rounding the results to the given decimal position. For instance, it would format 15233.345 to 15,233.35. If the given decimal position is 0, it rounds to return no decimal point or fractional part. You can optionally specify a locale value to format numbers to the pattern appropriate for the given region. Examples -------- SELECT FORMAT(1234567890.09876543210, 4) AS 'Format'; +--------------------+ | Format | +--------------------+ | 1,234,567,890.0988 | +--------------------+ SELECT FORMAT(1234567.89, 4) AS 'Format'; +----------------+ | Format | +----------------+ | 1,234,567.8900 | +----------------+ SELECT FORMAT(1234567.89, 0) AS 'Format'; +-----------+ | Format | +-----------+ | 1,234,568 | +-----------+ SELECT FORMAT(123456789,2,'rm_CH') AS 'Format'; +----------------+ | Format | +----------------+ | 123'456'789,00 | +----------------+ URL: https://mariadb.com/kb/en/format/https://mariadb.com/kb/en/format/m aIo, W K&%FROM_BASE64The FROM_BASE64() function was introduced in MariaDB 10.0.5. Syntax ------ FROM_BASE64(str) Description ----------- Decodes the given base-64 encode string, returning the result as a binary string. Returns NULL if the given string is NULL or if it's invalid. It is the reverse of the TO_BASE64 function. There are numerous methods to base-64 encode a string. MariaDB uses the following: It encodes alphabet value 64 as '+'. It encodes alphabet value 63 as '/'. It codes output in groups of four printable characters. Each three byte of data encoded uses four characters. If the final group is incomplete, it pads the difference with the '=' character. It divides long output, adding a new line very 76 characters. In decoding, it recognizes and ignores newlines, carriage returns, tabs and space whitespace characters. SELECT TO_BASE64('Maria') AS 'Input'; +-----------+ | Input | +-----------+ | TWFyaWE= | +-----------+ SELECT FROM_BASE64('TWFyaWE=') AS 'Output'; +--------+ | Output | +--------+ | Maria | +--------+ URL: https://mariadb.com/kb/en/from_base64/https://mariadb.com/kb/en/from_base64/X]%HEXSyntax ------ HEX(N_or_S) Description ----------- If N_or_S is a number, returns a string representation of the hexadecimal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,16). If N_or_S is a string, returns a hexadecimal string representation of N_or_S where each byte of each character in N_or_S is converted to two hexadecimal digits. If N_or_S is NULL, returns NULL. The inverse of this operation is performed by the UNHEX() function. Examples -------- SELECT HEX(255); +----------+ | HEX(255) | +----------+ | FF | +----------+ SELECT 0x4D617269614442; +------------------+ | 0x4D617269614442 | +------------------+ | MariaDB | +------------------+ SELECT HEX('MariaDB'); +----------------+ | HEX('MariaDB') | +----------------+ | 4D617269614442 | +----------------+ URL: https://mariadb.com/kb/en/hex/https://mariadb.com/kb/en/hex/Yu*%INSERT FunctionSyntax ------ INSERT(str,pos,len,newstr) Description ----------- Returns the string str, with the substring beginning at position pos and len characters long replaced by the string newstr. Returns the original string if pos is not within the length of the string. Replaces the rest of the string from position pos if len is not within the length of the rest of the string. Returns NULL if any argument is NULL. Examples -------- SELECT INSERT('Quadratic', 3, 4, 'What'); +-----------------------------------+ | INSERT('Quadratic', 3, 4, 'What') | +-----------------------------------+ | QuWhattic | +-----------------------------------+ SELECT INSERT('Quadratic', -1, 4, 'What'); +------------------------------------+ | INSERT('Quadratic', -1, 4, 'What') | +------------------------------------+ | Quadratic | +------------------------------------+ SELECT INSERT('Quadratic', 3, 100, 'What'); +-------------------------------------+ | INSERT('Quadratic', 3, 100, 'What') | +-------------------------------------+ | QuWhat | +-------------------------------------+ URL: https://mariadb.com/kb/en/insert-function/https://mariadb.com/kb/en/insert-function/];!%LENGTHSyntax ------ LENGTH(str) Description ----------- Returns the length of the string str, measured in bytes. A multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, LENGTH() returns 10, whereas CHAR_LENGTH() returns 5. If str is not a string value, it is converted into a string. If str is NULL, the function returns NULL. Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits. Oracle Mode When running Oracle mode from MariaDB 10.3, LENGTH() is a synonym for CHAR_LENGTH(). Examples -------- SELECT LENGTH('MariaDB'); +-------------------+ | LENGTH('MariaDB') | +-------------------+ | 7 | +-------------------+ SELECT LENGTH('π'); +--------------+ | LENGTH('π') | +--------------+ | 2 | +--------------+ In Oracle mode from MariaDB 10.3: SELECT LENGTH('π'); +--------------+ | LENGTH('π') | +--------------+ | 1 | +--------------+ URL: https://mariadb.com/kb/en/length/https://mariadb.com/kb/en/length/` $%LOAD_FILESyntax ------ LOAD_FILE(file_name) Description ----------- Reads the file and returns the file contents as a string. To use this function, the file must be located on the server host, you must specify the full path name to the file, and you must have the FILE privilege. The file must be readable by all and it must be less than the size, in bytes, of the max_allowed_packet system variable. If the secure_file_priv system variable is set to a non-empty directory name, the file to be loaded must be located in that directory. If the file does not exist or cannot be read because one of the preceding conditions is not satisfied, the function returns NULL. Since MariaDB 5.1, the character_set_filesystem system variable has controlled interpretation of file names that are given as literal strings. Statements using the LOAD_FILE() function are not safe for statement based replication. This is because the slave will execute the LOAD_FILE() command itself. If the file doesn't exist on the slave, the function will return NULL. Examples -------- UPDATE t SET blob_col=LOAD_FILE('/tmp/picture') WHERE id=1; URL: https://mariadb.com/kb/en/load_file/https://mariadb.com/kb/en/load_file/N p" 4_. _%LIKESyntax ------ expr LIKE pat [ESCAPE 'escape_char'] expr NOT LIKE pat [ESCAPE 'escape_char'] Description ----------- Tests whether expr matches the pattern pat. Returns either 1 (TRUE) or 0 (FALSE). Both expr and pat may be any valid expression and are evaluated to strings. Patterns may use the following wildcard characters: % matches any number of characters, including zero. _ matches any single character. Use NOT LIKE to test if a string does not match a pattern. This is equivalent to using the NOT operator on the entire LIKE expression. If either the expression or the pattern is NULL, the result is NULL. LIKE performs case-insensitive substring matches if the collation for the expression and pattern is case-insensitive. For case-sensitive matches, declare either argument to use a binary collation using COLLATE, or coerce either of them to a BINARY string using CAST. Use SHOW COLLATION to get a list of available collations. Collations ending in _bin are case-sensitive. Numeric arguments are coerced to binary strings. The _ wildcard matches a single character, not byte. It will only match a multi-byte character if it is valid in the expression's character set. For example, _ will match _utf8"€", but it will not match _latin1"€" because the Euro sign is not a valid latin1 character. If necessary, use CONVERT to use the expression in a different character set. If you need to match the characters _ or %, you must escape them. By default, you can prefix the wildcard characters the backslash character \ to escape them. The backslash is used both to encode special characters like newlines when a string is parsed as well as to escape wildcards in a pattern after parsing. Thus, to match an actual backslash, you sometimes need to double-escape it as "\\\\". To avoid difficulties with the backslash character, you can change the wildcard escape character using ESCAPE in a LIKE expression. The argument to ESCAPE must be a single-character string. Examples -------- Select the days that begin with "T": CREATE TABLE t1 (d VARCHAR(16)); INSERT INTO t1 VALUES ("Monday"), ("Tuesday"), ("Wednesday"), ("Thursday"), ("Friday"), ("Saturday"), ("Sunday"); SELECT * FROM t1 WHERE d LIKE "T%"; SELECT * FROM t1 WHERE d LIKE "T%"; +----------+ | d | +----------+ | Tuesday | | Thursday | +----------+ Select the days that contain the substring "es": SELECT * FROM t1 WHERE d LIKE "%es%"; SELECT * FROM t1 WHERE d LIKE "%es%"; +-----------+ | d | +-----------+ | Tuesday | | Wednesday | +-----------+ Select the six-character day names: SELECT * FROM t1 WHERE d like "___day"; SELECT * FROM t1 WHERE d like "___day"; +---------+ | d | +---------+ | Monday | | Friday | | Sunday | +---------+ With the default collations, LIKE is case-insensitive: SELECT * FROM t1 where d like "t%"; SELECT * FROM t1 where d like "t%"; +----------+ | d | +----------+ | Tuesday | | Thursday | +----------+ Use COLLATE to specify a binary collation, forcing case-sensitive matches: SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin; SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin; Empty set (0.00 sec) You can include functions and operators in the expression to match. Select dates based on their day name: CREATE TABLE t2 (d DATETIME); INSERT INTO t2 VALUES ("2007-01-30 21:31:07"), ("1983-10-15 06:42:51"), ("2011-04-21 12:34:56"), ("2011-10-30 06:31:41"), ("2011-01-30 14:03:25"), ("2004-10-07 11:19:34"); SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%"; SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%"; +------------------+ | d | +------------------+ | 2007-01-30 21:31 | | 2011-04-21 12:34 | | 2004-10-07 11:19 | +------------------+ 3 rows in set, 7 warnings (0.00 sec) Optimizing LIKE MariaDB can use indexes for LIKE on string columns in the case where the LIKE doesn't start with % or _. Starting from MariaDB 10.0, one can set the optimizer_use_condition_selectivity variable to 5. If this is done, then the optimizer will read optimizer_selectivity_sampling_limit rows to calculate the selectivity of the LIKE expression before starting to calculate the query plan. This can help speed up some LIKE queries by providing the optimizer with more information about your data. URL: https://mariadb.com/kb/en/like/https://mariadb.com/kb/en/like/a!%LOCATESyntax ------ LOCATE(substr,str), LOCATE(substr,str,pos) Description ----------- The first syntax returns the position of the first occurrence of substring substr in string str. The second syntax returns the position of the first occurrence of substring substr in string str, starting at position pos. Returns 0 if substr is not in str. LOCATE() performs a case-insensitive search. If any argument is NULL, returns NULL. INSTR() is a synonym of LOCATE() without the third argument. Examples -------- SELECT LOCATE('bar', 'foobarbar'); +----------------------------+ | LOCATE('bar', 'foobarbar') | +----------------------------+ | 4 | +----------------------------+ SELECT LOCATE('My', 'Maria'); +-----------------------+ | LOCATE('My', 'Maria') | +-----------------------+ | 0 | +-----------------------+ SELECT LOCATE('bar', 'foobarbar', 5); +-------------------------------+ | LOCATE('bar', 'foobarbar', 5) | +-------------------------------+ | 7 | +-------------------------------+ URL: https://mariadb.com/kb/en/locate/https://mariadb.com/kb/en/locate/I n)b %LOWERSyntax ------ LOWER(str) Description ----------- Returns the string str with all characters changed to lowercase according to the current character set mapping. The default is latin1 (cp1252 West European). Examples -------- SELECT LOWER('QUADRATICALLY'); +------------------------+ | LOWER('QUADRATICALLY') | +------------------------+ | quadratically | +------------------------+ LOWER() (and UPPER()) are ineffective when applied to binary strings (BINARY, VARBINARY, BLOB). To perform lettercase conversion, CONVERT the string to a non-binary string: SET @str = BINARY 'North Carolina'; SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1)); +----------------+-----------------------------------+ | LOWER(@str) | LOWER(CONVERT(@str USING latin1)) | +----------------+-----------------------------------+ | North Carolina | north carolina | +----------------+-----------------------------------+ URL: https://mariadb.com/kb/en/lower/https://mariadb.com/kb/en/lower/co%LPADSyntax ------ LPAD(str, len [,padstr]) Description ----------- Returns the string str, left-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters. If padstr is omitted, the LPAD function pads spaces. Prior to MariaDB 10.3.1, the padstr parameter was mandatory. Returns NULL if given a NULL argument. If the result is empty (zero length), returns either an empty string or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL. The Oracle mode version of the function can be accessed outside of Oracle mode by using LPAD_ORACLE as the function name. Examples -------- SELECT LPAD('hello',10,'.'); +----------------------+ | LPAD('hello',10,'.') | +----------------------+ | .....hello | +----------------------+ SELECT LPAD('hello',2,'.'); +---------------------+ | LPAD('hello',2,'.') | +---------------------+ | he | +---------------------+ From MariaDB 10.3.1, with the pad string defaulting to space. SELECT LPAD('hello',10); +------------------+ | LPAD('hello',10) | +------------------+ | hello | +------------------+ Oracle mode version from MariaDB 10.3.6: SELECT LPAD('',0),LPAD_ORACLE('',0); +------------+-------------------+ | LPAD('',0) | LPAD_ORACLE('',0) | +------------+-------------------+ | | NULL | +------------+-------------------+ URL: https://mariadb.com/kb/en/lpad/https://mariadb.com/kb/en/lpad/dW %LTRIMSyntax ------ LTRIM(str) Description ----------- Returns the string str with leading space characters removed. Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL. The Oracle mode version of the function can be accessed outside of Oracle mode by using LTRIM_ORACLE as the function name. Examples -------- SELECT QUOTE(LTRIM(' MariaDB ')); +-------------------------------+ | QUOTE(LTRIM(' MariaDB ')) | +-------------------------------+ | 'MariaDB ' | +-------------------------------+ Oracle mode version from MariaDB 10.3.6: SELECT LTRIM(''),LTRIM_ORACLE(''); +-----------+------------------+ | LTRIM('') | LTRIM_ORACLE('') | +-----------+------------------+ | | NULL | +-----------+------------------+ URL: https://mariadb.com/kb/en/ltrim/https://mariadb.com/kb/en/ltrim/e#%MAKE_SETSyntax ------ MAKE_SET(bits,str1,str2,...) Description ----------- Returns a set value (a string containing substrings separated by "," characters) consisting of the strings that have the corresponding bit in bits set. str1 corresponds to bit 0, str2 to bit 1, and so on. NULL values in str1, str2, ... are not appended to the result. Examples -------- SELECT MAKE_SET(1,'a','b','c'); +-------------------------+ | MAKE_SET(1,'a','b','c') | +-------------------------+ | a | +-------------------------+ SELECT MAKE_SET(1 | 4,'hello','nice','world'); +----------------------------------------+ | MAKE_SET(1 | 4,'hello','nice','world') | +----------------------------------------+ | hello,world | +----------------------------------------+ SELECT MAKE_SET(1 | 4,'hello','nice',NULL,'world'); +---------------------------------------------+ | MAKE_SET(1 | 4,'hello','nice',NULL,'world') | +---------------------------------------------+ | hello | +---------------------------------------------+ SELECT QUOTE(MAKE_SET(0,'a','b','c')); +--------------------------------+ | QUOTE(MAKE_SET(0,'a','b','c')) | +--------------------------------+ | '' | +--------------------------------+ URL: https://mariadb.com/kb/en/make_set/https://mariadb.com/kb/en/make_set/f 0(%MATCH AGAINSTSyntax ------ MATCH (col1,col2,...) AGAINST (expr [search_modifier]) Description ----------- A special construct used to perform a fulltext search on a fulltext index. See Fulltext Index Overview for a full description, and Full-text Indexes for more articles on the topic. Examples -------- CREATE TABLE ft_myisam(copy TEXT,FULLTEXT(copy)) ENGINE=MyISAM; INSERT INTO ft_myisam(copy) VALUES ('Once upon a time'), ('There was a wicked witch'), ('Who ate everybody up'); SELECT * FROM ft_myisam WHERE MATCH(copy) AGAINST('wicked'); +--------------------------+ | copy | +--------------------------+ | There was a wicked witch | +--------------------------+ SELECT id, body, MATCH (title,body) AGAINST ('Security implications of running MySQL as root' IN NATURAL LANGUAGE MODE) AS score FROM articles WHERE MATCH (title,body) AGAINST ('Security implications of running MySQL as root' IN NATURAL LANGUAGE MODE); +----+-------------------------------------+-----------------+ | id | body | score | +----+-------------------------------------+-----------------+ | 4 | 1. Never run mysqld as root. 2. ... | 1.5219271183014 | | 6 | When configured properly, MySQL ... | 1.3114095926285 | +----+-------------------------------------+-----------------+ URL: https://mariadb.com/kb/en/match-against/https://mariadb.com/kb/en/match-against/Ls2   ؇ n '%REGEXP_INSTRREGEXP_INSTR was introduced in MariaDB 10.0.5. Syntax ------ REGEXP_INSTR(subject, pattern) Returns the position of the first occurrence of the regular expression pattern in the string subject, or 0 if pattern was not found. The positions start with 1 and are measured in characters (i.e. not in bytes), which is important for multi-byte character sets. You can cast a multi-byte character set to BINARY to get offsets in bytes. The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data. The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags. MariaDB 10.0.5 switched to the PCRE regular expression library for enhanced regular expression performance, and REGEXP_INSTR was introduced as part of this enhancement. Examples -------- SELECT REGEXP_INSTR('abc','b'); -> 2 SELECT REGEXP_INSTR('abc','x'); -> 0 SELECT REGEXP_INSTR('BJÖRN','N'); -> 5 Casting a multi-byte character set as BINARY to get offsets in bytes: SELECT REGEXP_INSTR(BINARY 'BJÖRN','N') AS cast_utf8_to_binary; -> 6 Case sensitivity: SELECT REGEXP_INSTR('ABC','b'); -> 2 SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'b'); -> 0 SELECT REGEXP_INSTR(BINARY'ABC','b'); -> 0 SELECT REGEXP_INSTR('ABC','(?-i)b'); -> 0 SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'(?i)b'); -> 2 URL: https://mariadb.com/kb/en/regexp_instr/https://mariadb.com/kb/en/regexp_instr/o)%REGEXP_REPLACEREGEXP_REPLACE was introduced in MariaDB 10.0.5. Syntax ------ REGEXP_REPLACE(subject, pattern, replace) Description ----------- REGEXP_REPLACE returns the string subject with all occurrences of the regular expression pattern replaced by the string replace. If no occurrences are found, then subject is returned as is. The replace string can have backreferences to the subexpressions in the form \N, where N is a number from 1 to 9. The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data. The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags. MariaDB 10.0.5 switched to the PCRE regular expression library for enhanced regular expression performance, and REGEXP_REPLACE was introduced as part of this enhancement. MariaDB 10.0.11 introduced the default_regex_flags variable to address the remaining compatibilities between PCRE and the old regex library. Examples -------- SELECT REGEXP_REPLACE('ab12cd','[0-9]','') AS remove_digits; -> abcd SELECT REGEXP_REPLACE('titlebody', '',' ') AS strip_html; -> title body Backreferences to the subexpressions in the form \N, where N is a number from 1 to 9: SELECT REGEXP_REPLACE('James Bond','^(.*) (.*)$','\\2, \\1') AS reorder_name; -> Bond, James Case insensitive and case sensitive matches: SELECT REGEXP_REPLACE('ABC','b','-') AS case_insensitive; -> A-C SELECT REGEXP_REPLACE('ABC' COLLATE utf8_bin,'b','-') AS case_sensitive; -> ABC SELECT REGEXP_REPLACE(BINARY 'ABC','b','-') AS binary_data; -> ABC Overwriting the collation case sensitivity using the (?i) and (?-i) PCRE flags. SELECT REGEXP_REPLACE('ABC','(?-i)b','-') AS force_case_sensitive; -> ABC SELECT REGEXP_REPLACE(BINARY 'ABC','(?i)b','-') AS force_case_insensitive; -> A-C URL: https://mariadb.com/kb/en/regexp_replace/https://mariadb.com/kb/en/regexp_replace/p c(%REGEXP_SUBSTRREGEXP_SUBSTR was introduced in MariaDB 10.0.5. Syntax ------ REGEXP_SUBSTR(subject,pattern) Description ----------- Returns the part of the string subject that matches the regular expression pattern, or an empty string if pattern was not found. The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data. The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags. MariaDB 10.0.5 switched to the PCRE regular expression library for enhanced regular expression performance, and REGEXP_SUBSTR was introduced as part of this enhancement. MariaDB 10.0.11 introduced the default_regex_flags variable to address the remaining compatibilities between PCRE and the old regex library. Examples -------- SELECT REGEXP_SUBSTR('ab12cd','[0-9]+'); -> 12 SELECT REGEXP_SUBSTR( 'See https://mariadb.org/en/foundation/ for details', 'https?://[^/]*'); -> https://mariadb.org SELECT REGEXP_SUBSTR('ABC','b'); -> B SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'b'); -> SELECT REGEXP_SUBSTR(BINARY'ABC','b'); -> SELECT REGEXP_SUBSTR('ABC','(?i)b'); -> B SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'(?+i)b'); -> B URL: https://mariadb.com/kb/en/regexp_substr/https://mariadb.com/kb/en/regexp_substr/PF  :uBu%RPADSyntax ------ RPAD(str, len [, padstr]) Description ----------- Returns the string str, right-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters. If padstr is omitted, the RPAD function pads spaces. Prior to MariaDB 10.3.1, the padstr parameter was mandatory. Returns NULL if given a NULL argument. If the result is empty (a length of zero), returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL. The Oracle mode version of the function can be accessed outside of Oracle mode by using RPAD_ORACLE as the function name. Examples -------- SELECT RPAD('hello',10,'.'); +----------------------+ | RPAD('hello',10,'.') | +----------------------+ | hello..... | +----------------------+ SELECT RPAD('hello',2,'.'); +---------------------+ | RPAD('hello',2,'.') | +---------------------+ | he | +---------------------+ From MariaDB 10.3.1, with the pad string defaulting to space. SELECT RPAD('hello',30); +--------------------------------+ | RPAD('hello',30) | +--------------------------------+ | hello | +--------------------------------+ Oracle mode version from MariaDB 10.3.6: SELECT RPAD('',0),RPAD_ORACLE('',0); +------------+-------------------+ | RPAD('',0) | RPAD_ORACLE('',0) | +------------+-------------------+ | | NULL | +------------+-------------------+ URL: https://mariadb.com/kb/en/rpad/https://mariadb.com/kb/en/rpad/vO %RTRIMSyntax ------ RTRIM(str) Description ----------- Returns the string str with trailing space characters removed. Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL. The Oracle mode version of the function can be accessed outside of Oracle mode by using RTRIM_ORACLE as the function name. Examples -------- SELECT QUOTE(RTRIM('MariaDB ')); +-----------------------------+ | QUOTE(RTRIM('MariaDB ')) | +-----------------------------+ | 'MariaDB' | +-----------------------------+ Oracle mode version from MariaDB 10.3.6: SELECT RTRIM(''),RTRIM_ORACLE(''); +-----------+------------------+ | RTRIM('') | RTRIM_ORACLE('') | +-----------+------------------+ | | NULL | +-----------+------------------+ URL: https://mariadb.com/kb/en/rtrim/https://mariadb.com/kb/en/rtrim/w"%SOUNDEXSyntax ------ SOUNDEX(str) Description ----------- Returns a soundex string from str. Two strings that sound almost the same should have identical soundex strings. A standard soundex string is four characters long, but the SOUNDEX() function returns an arbitrarily long string. You can use SUBSTRING() on the result to get a standard soundex string. All non-alphabetic characters in str are ignored. All international alphabetic characters outside the A-Z range are treated as vowels. Important: When using SOUNDEX(), you should be aware of the following limitations: This function, as currently implemented, is intended to work well with strings that are in the English language only. Strings in other languages may not produce reliable results. Examples -------- SOUNDEX('Hello'); +------------------+ | SOUNDEX('Hello') | +------------------+ | H400 | +------------------+ SELECT SOUNDEX('MariaDB'); +--------------------+ | SOUNDEX('MariaDB') | +--------------------+ | M631 | +--------------------+ SELECT SOUNDEX('Knowledgebase'); +--------------------------+ | SOUNDEX('Knowledgebase') | +--------------------------+ | K543212 | +--------------------------+ SELECT givenname, surname FROM users WHERE SOUNDEX(givenname) = SOUNDEX("robert"); +-----------+---------+ | givenname | surname | +-----------+---------+ | Roberto | Castro | +-----------+---------+ URL: https://mariadb.com/kb/en/soundex/https://mariadb.com/kb/en/soundex/| G $%SUBSTRINGSyntax ------ SUBSTRING(str,pos), SUBSTRING(str FROM pos), SUBSTRING(str,pos,len), SUBSTRING(str FROM pos FOR len) SUBSTR(str,pos), SUBSTR(str FROM pos), SUBSTR(str,pos,len), SUBSTR(str FROM pos FOR len) Description ----------- The forms without a len argument return a substring from string str starting at position pos. The forms with a len argument return a substring len characters long from string str, starting at position pos. The forms that use FROM are standard SQL syntax. It is also possible to use a negative value for pos. In this case, the beginning of the substring is pos characters from the end of the string, rather than the beginning. A negative value may be used for pos in any of the forms of this function. By default, the position of the first character in the string from which the substring is to be extracted is reckoned as 1. For Oracle-compatibility, from MariaDB 10.3.3, when sql_mode is set to 'oracle', position zero is treated as position 1 (although the first character is still reckoned as 1). If any argument is NULL, returns NULL. Examples -------- SELECT SUBSTRING('Knowledgebase',5); +------------------------------+ | SUBSTRING('Knowledgebase',5) | +------------------------------+ | ledgebase | +------------------------------+ SELECT SUBSTRING('MariaDB' FROM 6); +-----------------------------+ | SUBSTRING('MariaDB' FROM 6) | +-----------------------------+ | DB | +-----------------------------+ SELECT SUBSTRING('Knowledgebase',3,7); +--------------------------------+ | SUBSTRING('Knowledgebase',3,7) | +--------------------------------+ | owledge | +--------------------------------+ SELECT SUBSTRING('Knowledgebase', -4); +--------------------------------+ | SUBSTRING('Knowledgebase', -4) | +--------------------------------+ | base | +--------------------------------+ SELECT SUBSTRING('Knowledgebase', -8, 4); +-----------------------------------+ | SUBSTRING('Knowledgebase', -8, 4) | +-----------------------------------+ | edge | +-----------------------------------+ SELECT SUBSTRING('Knowledgebase' FROM -8 FOR 4); +------------------------------------------+ | SUBSTRING('Knowledgebase' FROM -8 FOR 4) | +------------------------------------------+ | edge | +------------------------------------------+ Oracle mode from MariaDB 10.3.3: SELECT SUBSTR('abc',0,3); +-------------------+ | SUBSTR('abc',0,3) | +-------------------+ | | +-------------------+ SELECT SUBSTR('abc',1,2); +-------------------+ | SUBSTR('abc',1,2) | +-------------------+ | ab | +-------------------+ SET sql_mode='oracle'; SELECT SUBSTR('abc',0,3); +-------------------+ | SUBSTR('abc',0,3) | +-------------------+ | abc | +-------------------+ SELECT SUBSTR('abc',1,2); +-------------------+ | SUBSTR('abc',1,2) | +-------------------+ | ab | +-------------------+ URL: https://mariadb.com/kb/en/substring/https://mariadb.com/kb/en/substring/( `  P1 }:*%SUBSTRING_INDEXSyntax ------ SUBSTRING_INDEX(str,delim,count) Description ----------- Returns the substring from string str before count occurrences of the delimiter delim. If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. SUBSTRING_INDEX() performs a case-sensitive match when searching for delim. If any argument is NULL, returns NULL. Examples -------- SELECT SUBSTRING_INDEX('www.mariadb.org', '.', 2); +--------------------------------------------+ | SUBSTRING_INDEX('www.mariadb.org', '.', 2) | +--------------------------------------------+ | www.mariadb | +--------------------------------------------+ SELECT SUBSTRING_INDEX('www.mariadb.org', '.', -2); +---------------------------------------------+ | SUBSTRING_INDEX('www.mariadb.org', '.', -2) | +---------------------------------------------+ | mariadb.org | +---------------------------------------------+ URL: https://mariadb.com/kb/en/substring_index/https://mariadb.com/kb/en/substring_index/~ $%TO_BASE64The TO_BASE64() function was introduced in MariaDB 10.0.5. Syntax ------ TO_BASE64(str) Description ----------- Converts the string argument str to its base-64 encoded form, returning the result as a character string in the connection character set and collation. The argument str will be converted to string first if it is not a string. A NULL argument will return a NULL result. The reverse function, FROM_BASE64(), decodes an encoded base-64 string. There are a numerous different methods to base-64 encode a string. The following are used by MariaDB and MySQL: Alphabet value 64 is encoded as '+'. Alphabet value 63 is encoded as '/'. Encoding output is made up of groups of four printable characters, with each three bytes of data encoded using four characters. If the final group is not complete, it is padded with '=' characters to make up a length of four. To divide long output, a newline is added after every 76 characters. Decoding will recognize and ignore newlines, carriage returns, tabs, and spaces. Examples -------- SELECT TO_BASE64('Maria'); +--------------------+ | TO_BASE64('Maria') | +--------------------+ | TWFyaWE= | +--------------------+ URL: https://mariadb.com/kb/en/to_base64/https://mariadb.com/kb/en/to_base64/%TRIMSyntax ------ TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM] str) Description ----------- Returns the string str with all remstr prefixes or suffixes removed. If none of the specifiers BOTH, LEADING, or TRAILING is given, BOTH is assumed. remstr is optional and, if not specified, spaces are removed. Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL. The Oracle mode version of the function can be accessed outside of Oracle mode by using TRIM_ORACLE as the function name. Examples -------- SELECT TRIM(' bar ')\G *************************** 1. row *************************** TRIM(' bar '): bar SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx')\G *************************** 1. row *************************** TRIM(LEADING 'x' FROM 'xxxbarxxx'): barxxx SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx')\G *************************** 1. row *************************** TRIM(BOTH 'x' FROM 'xxxbarxxx'): bar SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz')\G *************************** 1. row *************************** TRIM(TRAILING 'xyz' FROM 'barxxyz'): barx Oracle mode version from MariaDB 10.3.6: SELECT TRIM(''),TRIM_ORACLE(''); +----------+-----------------+ | TRIM('') | TRIM_ORACLE('') | +----------+-----------------+ | | NULL | +----------+-----------------+ URL: https://mariadb.com/kb/en/trim/https://mariadb.com/kb/en/trim/1 %UNHEXSyntax ------ UNHEX(str) Description ----------- Performs the inverse operation of HEX(str). That is, it interprets each pair of hexadecimal digits in the argument as a number and converts it to the character represented by the number. The resulting characters are returned as a binary string. If str is NULL, UNHEX() returns NULL. Examples -------- SELECT HEX('MariaDB'); +----------------+ | HEX('MariaDB') | +----------------+ | 4D617269614442 | +----------------+ SELECT UNHEX('4D617269614442'); +-------------------------+ | UNHEX('4D617269614442') | +-------------------------+ | MariaDB | +-------------------------+ SELECT 0x4D617269614442; +------------------+ | 0x4D617269614442 | +------------------+ | MariaDB | +------------------+ SELECT UNHEX(HEX('string')); +----------------------+ | UNHEX(HEX('string')) | +----------------------+ | string | +----------------------+ SELECT HEX(UNHEX('1267')); +--------------------+ | HEX(UNHEX('1267')) | +--------------------+ | 1267 | +--------------------+ URL: https://mariadb.com/kb/en/unhex/https://mariadb.com/kb/en/unhex/hd   $%UPDATEXMLSyntax ------ UpdateXML(xml_target, xpath_expr, new_xml) Description ----------- This function replaces a single portion of a given fragment of XML markup xml_target with a new XML fragment new_xml, and then returns the changed XML. The portion of xml_target that is replaced matches an XPath expression xpath_expr supplied by the user. If no expression matching xpath_expr is found, or if multiple matches are found, the function returns the original xml_target XML fragment. All three arguments should be strings. Examples -------- SELECT UpdateXML('ccc', '/a', 'fff') AS val1, UpdateXML('ccc', '/b', 'fff') AS val2, UpdateXML('ccc', '//b', 'fff') AS val3, UpdateXML('ccc', '/a/d', 'fff') AS val4, UpdateXML('ccc', '/a/d', 'fff') AS val5 \G *************************** 1. row *************************** val1: fff val2: ccc val3: fff val4: cccfff val5: ccc 1 row in set (0.00 sec) URL: https://mariadb.com/kb/en/updatexml/https://mariadb.com/kb/en/updatexml/ (%WEIGHT_STRINGThe WEIGHT_STRING function was introduced in MariaDB 10.0.5. Syntax ------ WEIGHT_STRING(str [AS {CHAR|BINARY}(N)] [LEVEL levels] [flags]) levels: N [ASC|DESC|REVERSE] [, N [ASC|DESC|REVERSE]] ... Description ----------- Returns a binary string representing the string's sorting and comparison value. A string with a lower result means that for sorting purposes the string appears before a string with a higher result. WEIGHT_STRING() is particularly useful when adding new collations, for testing purposes. If str is a non-binary string (CHAR, VARCHAR or TEXT), WEIGHT_STRING returns the string's collation weight. If str is a binary string (BINARY, VARBINARY or BLOB), the return value is simply the input value, since the weight for each byte in a binary string is the byte value. WEIGHT_STRING() returns NULL if given a NULL input. The optional AS clause permits casting the input string to a binary or non-binary string, as well as to a particular length. AS BINARY(N) measures the length in bytes rather than characters, and right pads with 0x00 bytes to the desired length. AS CHAR(N) measures the length in characters, and right pads with spaces to the desired length. N has a minimum value of 1, and if it is less than the length of the input string, the string is truncated without warning. The optional LEVEL clause specifies that the return value should contain weights for specific collation levels. The levels specifier can either be a single integer, a comma-separated list of integers, or a range of integers separated by a dash (whitespace is ignored). Integers can range from 1 to a maximum of 6, dependent on the collation, and need to be listed in ascending order. If the LEVEL clause is no provided, a default of 1 to the maximum for the collation is assumed. If the LEVEL is specified without using a range, an optional modifier is permitted. ASC, the default, returns the weights without any modification. DESC returns bitwise-inverted weights. REVERSE returns the weights in reverse order. Examples -------- The examples below use the HEX() function to represent non-printable results in hexadecimal format. SELECT HEX(WEIGHT_STRING('x')); +-------------------------+ | HEX(WEIGHT_STRING('x')) | +-------------------------+ | 0058 | +-------------------------+ SELECT HEX(WEIGHT_STRING('x' AS BINARY(4))); +--------------------------------------+ | HEX(WEIGHT_STRING('x' AS BINARY(4))) | +--------------------------------------+ | 78000000 | +--------------------------------------+ SELECT HEX(WEIGHT_STRING('x' AS CHAR(4))); +------------------------------------+ | HEX(WEIGHT_STRING('x' AS CHAR(4))) | +------------------------------------+ | 0058002000200020 | +------------------------------------+ SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1)); +--------------------------------------+ | HEX(WEIGHT_STRING(0xaa22ee LEVEL 1)) | +--------------------------------------+ | AA22EE | +--------------------------------------+ SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC)); +-------------------------------------------+ | HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC)) | +-------------------------------------------+ | 55DD11 | +-------------------------------------------+ SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE)); +----------------------------------------------+ | HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE)) | +----------------------------------------------+ | EE22AA | +----------------------------------------------+ URL: https://mariadb.com/kb/en/weight_string/https://mariadb.com/kb/en/weight_string/ )'ALTER DATABASEModifies a database, changing its overall characteristics. Syntax ------ ALTER {DATABASE | SCHEMA} [db_name] alter_specification ... ALTER {DATABASE | SCHEMA} db_name UPGRADE DATA DIRECTORY NAME alter_specification: [DEFAULT] CHARACTER SET [=] charset_name | [DEFAULT] COLLATE [=] collation_name Description ----------- ALTER DATABASE enables you to change the overall characteristics of a database. These characteristics are stored in the db.opt file in the database directory. To use ALTER DATABASE, you need the ALTER privilege on the database. ALTER SCHEMA is a synonym for ALTER DATABASE. The CHARACTER SET clause changes the default database character set. The COLLATE clause changes the default database collation. See Character Sets and Collations for more. You can see what character sets and collations are available using, respectively, the SHOW CHARACTER SET and SHOW COLLATION statements. Changing the default character set/collation of a database does not change the character set/collation of any stored procedures or stored functions that were previously created, and relied on the defaults. These need to be dropped and recreated in order to apply the character set/collation changes. The database name can be omitted from the first syntax, in which case the statement applies to the default database. The syntax that includes the UPGRADE DATA DIRECTORY NAME clause was added in MySQL 5.1.23. It updates the name of the directory associated with the database to use the encoding implemented in MySQL 5.1 for mapping database names to database directory names (see Identifier to File Name Mapping). This clause is for use under these conditions: It is intended when upgrading MySQL to 5.1 or later from older versions. It is intended to update a database directory name to the current encoding format if the name contains special characters that need encoding. The statement is used by mysqlcheck (as invoked by mysql_upgrade). For example,if a database in MySQL 5.0 has a name of a-b-c, the name contains instance of the `-' character. In 5.0, the database directory is also named a-b-c, which is not necessarily safe for all file systems. In MySQL 5.1 and up, the same database name is encoded as a@002db@002dc to produce a file system-neutral directory name. When a MySQL installation is upgraded to MySQL 5.1 or later from an older version,the server displays a name such as a-b-c (which is in the old format) as #mysql50#a-b-c, and you must refer to the name using the #mysql50# prefix. Use UPGRADE DATA DIRECTORY NAME in this case to explicitly tell the server to re-encode the database directory name to the current encoding format: ALTER DATABASE `#mysql50#a-b-c` UPGRADE DATA DIRECTORY NAME; After executing this statement, you can refer to the database as a-b-c without the special #mysql50# prefix. Examples -------- ALTER DATABASE test CHARACTER SET = 'utf8' COLLATE = 'utf8_bin'; URL: https://mariadb.com/kb/en/alter-database/https://mariadb.com/kb/en/alter-database/3 1 @X &'ALTER EVENTModifies one or more characteristics of an existing event. Syntax ------ ALTER [DEFINER = { user | CURRENT_USER }] EVENT event_name [ON SCHEDULE schedule] [ON COMPLETION [NOT] PRESERVE] [RENAME TO new_event_name] [ENABLE | DISABLE | DISABLE ON SLAVE] [COMMENT 'comment'] [DO sql_statement] Description ----------- The ALTER EVENT statement is used to change one or more of the characteristics of an existing event without the need to drop and recreate it. The syntax for each of the DEFINER, ON SCHEDULE, ON COMPLETION, COMMENT, ENABLE / DISABLE, and DO clauses is exactly the same as when used with CREATE EVENT. This statement requires the EVENT privilege. When a user executes a successful ALTER EVENT statement, that user becomes the definer for the affected event. (In MySQL 5.1.11 and earlier, an event could be altered only by its definer, or by a user having the SUPER privilege.) ALTER EVENT works only with an existing event: ALTER EVENT no_such_event ON SCHEDULE EVERY '2:3' DAY_HOUR; ERROR 1539 (HY000): Unknown event 'no_such_event' Examples -------- ALTER EVENT myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 2 HOUR DO UPDATE myschema.mytable SET mycol = mycol + 1; URL: https://mariadb.com/kb/en/alter-event/https://mariadb.com/kb/en/alter-event/)'ALTER FUNCTIONSyntax ------ ALTER FUNCTION func_name [characteristic ...] characteristic: { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string' Description ----------- This statement can be used to change the characteristics of a stored function. More than one change may be specified in an ALTER FUNCTION statement. However, you cannot change the parameters or body of a stored function using this statement; to make such changes, you must drop and re-create the function using DROP FUNCTION and CREATE FUNCTION. You must have the ALTER ROUTINE privilege for the function. (That privilege is granted automatically to the function creator.) If binary logging is enabled, the ALTER FUNCTION statement might also require the SUPER privilege, as described in Binary Logging of Stored Routines. Example ALTER FUNCTION hello SQL SECURITY INVOKER; URL: https://mariadb.com/kb/en/alter-function/https://mariadb.com/kb/en/alter-function/*'ALTER PROCEDURESyntax ------ ALTER PROCEDURE proc_name [characteristic ...] characteristic: { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string' Description ----------- This statement can be used to change the characteristics of a stored procedure. More than one change may be specified in an ALTER PROCEDURE statement. However, you cannot change the parameters or body of a stored procedure using this statement. To make such changes, you must drop and re-create the procedure using either CREATE OR REPLACE PROCEDURE (since MariaDB 10.1.3) or DROP PROCEDURE and CREATE PROCEDURE (MariaDB 10.1.2 and before). You must have the ALTER ROUTINE privilege for the procedure. By default, that privilege is granted automatically to the procedure creator. See Stored Routine Privileges. Example ALTER PROCEDURE simpleproc SQL SECURITY INVOKER; URL: https://mariadb.com/kb/en/alter-procedure/https://mariadb.com/kb/en/alter-procedure/ %'ALTER VIEWSyntax ------ ALTER [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}] [DEFINER = { user | CURRENT_USER }] [SQL SECURITY { DEFINER | INVOKER }] VIEW view_name [(column_list)] AS select_statement [WITH [CASCADED | LOCAL] CHECK OPTION] Description ----------- This statement changes the definition of a view, which must exist. The syntax is similar to that for CREATE VIEW and the effect is the same as for CREATE OR REPLACE VIEW if the view exists. This statement requires the CREATE VIEW and DROP privileges for the view, and some privilege for each column referred to in the SELECT statement. As of MariaDB 5.1.23, ALTER VIEW is allowed only to the definer or users with the SUPER privilege. Example ALTER VIEW v AS SELECT a, a*3 AS a2 FROM t; URL: https://mariadb.com/kb/en/alter-view/https://mariadb.com/kb/en/alter-view/*'CREATE DATABASESyntax ------ CREATE [OR REPLACE] {DATABASE | SCHEMA} [IF NOT EXISTS] db_name [create_specification] ... create_specification: [DEFAULT] CHARACTER SET [=] charset_name | [DEFAULT] COLLATE [=] collation_name Description ----------- CREATE DATABASE creates a database with the given name. To use this statement, you need the CREATE privilege for the database. CREATE SCHEMA is a synonym for CREATE DATABASE. For valid identifiers to use as database names, see Identifier Names. OR REPLACE The OR REPLACE clause was added in MariaDB 10.1.3 If the optional OR REPLACE clause is used, it acts as a shortcut for: DROP DATABASE IF EXISTS db_name; CREATE DATABASE db_name ...; IF NOT EXISTS When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified database already exists. Examples -------- CREATE DATABASE db1; Query OK, 1 row affected (0.18 sec) CREATE DATABASE db1; ERROR 1007 (HY000): Can't create database 'db1'; database exists CREATE OR REPLACE DATABASE db1; Query OK, 2 rows affected (0.00 sec) CREATE DATABASE IF NOT EXISTS db1; Query OK, 1 row affected, 1 warning (0.01 sec) SHOW WARNINGS; +-------+------+----------------------------------------------+ | Level | Code | Message | +-------+------+----------------------------------------------+ | Note | 1007 | Can't create database 'db1'; database exists | +-------+------+----------------------------------------------+ Setting the character sets and collation. See Setting Character Sets and Collations for more details. CREATE DATABASE czech_slovak_names CHARACTER SET = 'keybcs2' COLLATE = 'keybcs2_bin'; URL: https://mariadb.com/kb/en/create-database/https://mariadb.com/kb/en/create-database/> ]= : .@d")'ALTER SEQUENCEALTER SEQUENCE was introduced in MariaDB 10.3. Syntax ------ ALTER SEQUENCE [IF EXISTS] sequence_name [ INCREMENT [ BY | = ] increment ] [ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ] [ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ] [ START [ WITH | = ] start ] [ CACHE [=] cache ] [ [ NO ] CYCLE ] [ RESTART [[WITH | =] restart] ALTER SEQUENCE allows one to change any values for a SEQUENCE created with CREATE SEQUENCE. The options for ALTER SEQUENCE can be given in any order. Description ----------- ALTER SEQUENCE changes the parameters of an existing sequence generator. Any parameters not specifically set in the ALTER SEQUENCE command retain their prior settings. ALTER SEQUENCE requires the ALTER privilege. Arguments to ALTER SEQUENCE The following options may be used: Option | Default value | Description | INCREMENT | 1 | Increment to use for values. May be negative. | MINVALUE | 1 if INCREMENT > 0 and -9223372036854775807 if INCREMENT < 0 | Minimum value for the sequence. | MAXVALUE | 9223372036854775806 if INCREMENT > 0 and -1 if INCREMENT < 0 | Max value for sequence. | START | MINVALUE if INCREMENT > 0 and MAX_VALUE if INCREMENT< 0 | First value that the sequence will generate. | CACHE | 1000 | Number of values that should be cached. 0 if no CACHE. The underlying table will be updated first time a new sequence number is generated and each time the cache runs out. | CYCLE | 0 (= NO CYCLE) | 1 if the sequence should start again from MINVALUE# after it has run out of values. | RESTART | START if restart value not is given |  If RESTART option is used, NEXT VALUE will return the restart value. | The optional clause RESTART [ WITH restart ] sets the next value for the sequence. This is equivalent to calling the SETVAL() function with the is_used argument as 0. The specified value will be returned by the next call of nextval. Using RESTART with no restart value is equivalent to supplying the start value that was recorded by CREATE SEQUENCE or last set by ALTER SEQUENCE START WITH. ALTER SEQUENCE will not allow you to change the sequence so that it's inconsistent. For example: CREATE SEQUENCE s1; ALTER SEQUENCE s1 MINVALUE 10; ERROR 4061 (HY000): Sequence 'test.t1' values are conflicting ALTER SEQUENCE s1 MINVALUE 10 RESTART 10; ERROR 4061 (HY000): Sequence 'test.t1' values are conflicting ALTER SEQUENCE s1 MINVALUE 10 START 10 RESTART 10; INSERT To allow SEQUENCE objects to be backed up by old tools, like mysqldump, one can use SELECT to read the current state of a SEQUENCE object and use an INSERT to update the SEQUENCE object. INSERT is only allowed if all fields are specified: CREATE SEQUENCE s1; INSERT INTO s1 VALUES(1000,10,2000,1005,1,1000,0,0); SELECT * FROM s1; +------------+-----------+-----------+-------+-----------+-------+-------+-------+ | next_value | min_value | max_value | start | increment | cache | cycle | round | +------------+-----------+-----------+-------+-----------+-------+-------+-------+ | 1000 | 10 | 2000 | 1005 | 1 | 1000 | 0 | 0 | +------------+-----------+-----------+-------+-----------+-------+-------+-------+ SHOW CREATE SEQUENCE s1; +-------+--------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +-------+--------------------------------------------------------------------------------------------------------------+ | s1 | CREATE SEQUENCE `s1` start with 1005 minvalue 10 maxvalue 2000 increment by 1 cache 1000 nocycle ENGINE=Aria | +-------+--------------------------------------------------------------------------------------------------------------+ Notes ALTER SEQUENCE will instantly affect all future SEQUENCE operations. This is in contrast to some other databases where the changes requested by ALTER SEQUENCE will not be seen until the sequence cache has run out. ALTER SEQUENCE will take a full table lock of the sequence object during its (brief) operation. This ensures that ALTER SEQUENCE is replicated correctly. If you only want to set the next sequence value to a higher value than current, then you should use SETVAL() instead, as this is not blocking. If you want to change storage engine, sequence comment or rename the sequence, you can use ALTER TABLE for this. URL: https://mariadb.com/kb/en/alter-sequence/https://mariadb.com/kb/en/alter-sequence/)'CREATE PACKAGEOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ CREATE [ OR REPLACE] [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }] PACKAGE [ IF NOT EXISTS ] [ db_name . ] package_name [ package_characteristic ... ] { AS | IS } [ package_specification_element ... ] END [ package_name ] package_characteristic: COMMENT 'string' | SQL SECURITY { DEFINER | INVOKER } package_specification_element: FUNCTION_SYM package_specification_function ; | PROCEDURE_SYM package_specification_procedure ; package_specification_function: func_name [ ( func_param [, func_param]... ) ] RETURNS func_return_type [ package_routine_characteristic... ] package_specification_procedure: proc_name [ ( proc_param [, proc_param]... ) ] [ package_routine_characteristic... ] func_return_type: type func_param: param_name type proc_param: param_name { IN | OUT | INOUT | IN OUT } type type: Any valid MariaDB explicit or anchored data type package_routine_characteristic: COMMENT 'string' | LANGUAGE SQL | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } Description ----------- The CREATE PACKAGE statement can be used when Oracle SQL_MODE is set. The CREATE PACKAGE creates the specification for a stored package (a collection of logically related stored objects). A stored package specification declares public routines (procedures and functions) of the package, but does not implement these routines. A package whose specification was created by the CREATE PACKAGE statement, should later be implemented using the CREATE PACKAGE BODY statement. Examples -------- SET sql_mode=ORACLE; DELIMITER $$ CREATE OR REPLACE PACKAGE employee_tools AS FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2); PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)); PROCEDURE raiseSalaryStd(eid INT); PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)); END; $$ DELIMITER ; URL: https://mariadb.com/kb/en/create-package/https://mariadb.com/kb/en/create-package/s gN+^Syntax ------ ALTER [ONLINE] [IGNORE] TABLE tbl_name [WAIT n | NOWAIT] alter_specification [, alter_specification] ... alter_specification: table_option ... | ADD [COLUMN] [IF NOT EXISTS] col_name column_definition [FIRST | AFTER col_name ] | ADD [COLUMN] [IF NOT EXISTS] (col_name column_definition,...) | ADD {INDEX|KEY} [IF NOT EXISTS] [index_name] [index_type] (index_col_name,...) [index_option] ... | ADD [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...) [index_option] ... | ADD [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY] [index_name] [index_type] (index_col_name,...) [index_option] ... | ADD FULLTEXT [INDEX|KEY] [index_name] (index_col_name,...) [index_option] ... | ADD SPATIAL [INDEX|KEY] [index_name] (index_col_name,...) [index_option] ... | ADD [CONSTRAINT [symbol]] FOREIGN KEY [IF NOT EXISTS] [index_name] (index_col_name,...) reference_definition | ADD PERIOD FOR SYSTEM_TIME (start_column_name, end_column_name) | ALTER [COLUMN] col_name SET DEFAULT literal | (expression) | ALTER [COLUMN] col_name DROP DEFAULT | CHANGE [COLUMN] [IF EXISTS] old_col_name new_col_name column_definition [FIRST|AFTER col_name] | MODIFY [COLUMN] [IF EXISTS] col_name column_definition [FIRST | AFTER col_name] | DROP [COLUMN] [IF EXISTS] col_name [RESTRICT|CASCADE] | DROP PRIMARY KEY | DROP {INDEX|KEY} [IF EXISTS] index_name | DROP FOREIGN KEY [IF EXISTS] fk_symbol | DROP CONSTRAINT [IF EXISTS] constraint_name | DISABLE KEYS | ENABLE KEYS | RENAME [TO] new_tbl_name | ORDER BY col_name [, col_name] ... | CONVERT TO CHARACTER SET charset_name [COLLATE collation_name] | [DEFAULT] CHARACTER SET [=] charset_name | [DEFAULT] COLLATE [=] collation_name | DISCARD TABLESPACE | IMPORT TABLESPACE | ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT} | LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE} | FORCE | partition_options | ADD PARTITION (partition_definition) | DROP PARTITION partition_names | COALESCE PARTITION number | REORGANIZE PARTITION [partition_names INTO (partition_definitions)] | ANALYZE PARTITION partition_names | CHECK PARTITION partition_names | OPTIMIZE PARTITION partition_names | REBUILD PARTITION partition_names | REPAIR PARTITION partition_names | EXCHANGE PARTITION partition_name WITH TABLE tbl_name | REMOVE PARTITIONING | ADD SYSTEM VERSIONING | DROP SYSTEM VERSIONING index_col_name: col_name [(length)] [ASC | DESC] index_type: USING {BTREE | HASH | RTREE} index_option: KEY_BLOCK_SIZE [=] value | index_type | WITH PARSER parser_name | COMMENT 'string' | CLUSTERING={YES| NO} table_options: table_option [[,] table_option] ... In MariaDB 10.0.2 and later, IF EXISTS and IF NOT EXISTS clauses have been added for the following: ADD COLUMN [IF NOT EXISTS] ADD INDEX [IF NOT EXISTS] ADD FOREIGN KEY [IF NOT EXISTS] ADD PARTITION [IF NOT EXISTS] CREATE INDEX [IF NOT EXISTS] DROP COLUMN [IF EXISTS] DROP INDEX [IF EXISTS] DROP FOREIGN KEY [IF EXISTS] DROP PARTITION [IF EXISTS] CHANGE COLUMN [IF EXISTS] MODIFY COLUMN [IF EXISTS] DROP INDEX [IF EXISTS] When IF EXISTS and IF NOT EXISTS are used in clauses, queries will not report errors when the condition is triggered for that clause. A warning with the same message text will be issued and the ALTER will move on to the next clause in the statement (or end if finished). This was done in MDEV-318. Description ----------- ALTER TABLE enables you to change the structure of an existing table. For example, you can add or delete columns, create or destroy indexes, change the type of existing columns, or rename columns or the table itself. You can also change the comment for the table and the storage engine of the table. If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables. When adding a UNIQUE index on a column (or a set of columns) which have duplicated values, an error will be produced and the statement will be stopped. To suppress the error and force the creation of UNIQUE indexes, discarding duplicates, the IGNORE option can be specified. This can be useful if a column (or a set of columns) should be UNIQUE but it contains duplicate values; however, this technique provides no control on which rows are preserved and which are deleted. Also, note that IGNORE is accepted but ignored in ALTER TABLE ... EXCHANGE PARTITION statements. This statement can also be used to rename a table. For details see RENAME TABLE. When an index is created, the storage engine may use a configurable buffer in the process. Incrementing the buffer speeds up the index creation. Aria and MyISAM allocate a buffer whose size is defined by aria_sort_buffer_size or myisam_sort_buffer_size, also used for REPAIR TABLE. InnoDB/XtraDB allocates three buffers whose size is defined by innodb_sort_buffer_size. Privileges Executing the ALTER TABLE statement generally requires at least the ALTER privilege for the table or the database.. If you are renaming a table, then it also requires the DROP, CREATE and INSERT privileges for the table or the database as well. Online DDL In MariaDB 10.0 and later, online DDL is supported with the ALGORITHM and LOCK clauses. See InnoDB Online DDL Overview for more information on online DDL with InnoDB. ALTER ONLINE TABLE ALTER ONLINE TABLE has also worked for partitioned tables since MariaDB 10.0.11. Online ALTER TABLE is available by executing the following: ALTER ONLINE TABLE ...; This statement has the following semantics: In MariaDB 10.0.12 and later, this statement is equivalent to the following: ALTER TABLE ... LOCK=NONE; See the LOCK alter specification for more information. In MariaDB 10.0.11, this statement is equivalent to the following: ALTER TABLE ... ALGORITHM=INPLACE; See the ALGORITHM alter specification for more information. MariaDB until 10.0.10 In MariaDB 10.0.10 and before, this statement ensures that the ALTER TABLE statement does not make a copy of the table. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. Column Definitions See CREATE TABLE: Column Definitions for information about column definitions. Index Definitions See CREATE TABLE: Index Definitions for information about index definitions. The CREATE INDEX and DROP INDEX statements can also be used to add or remove an index. Character Sets and Collations CONVERT TO CHARACTER SET charset_name [COLLATE collation_name] [DEFAULT] CHARACTER SET [=] charset_name [DEFAULT] COLLATE [=] collation_name See Setting Character Sets and Collations for details on setting the character sets and collations. Alter Specifications Table Options See CREATE TABLE: Table Options for information about table options. ADD COLUMN ... ADD COLUMN [IF NOT EXISTS] (col_name column_definition,...) Adds a column to the table. The syntax is the same as in CREATE TABLE. If you are using IF NOT_EXISTS the column will not be added if it was not there already. This is very useful when doing scripts to modify tables. The FIRST and AFTER clauses affect the physical order of columns in the datafile. Use FIRST to add a column in the first (leftmost) position, or AFTER followed by a column name to add the new column in any other position. Note that, nowadays, the physical position of a column is usually irrelevant. See also Instant ADD COLUMN for InnoDB. DROP COLUMN ... DROP COLUMN [IF EXISTS] col_name [CASCADE|RESTRICT] Drops the column from the table. If you are using IF EXISTS you will not get an error if the column didn't exist. If the column is part of any index, the column will be dropped from them, except if you add a new column with identical name at the same time. The index will be dropped if all columns from the index were dropped. If the column was used in a view or trigger, you will get an error next time the view or trigger is accessed. Dropping a column that is part of a multi-column UNIQUE constraint is not permitted. For example: CREATE TABLE a ( a int, b int, primary key (a,b) ); ALTER TABLE x DROP COLUMN a; [42000][1072] Key column 'A' doesny't exist in table The reason is that dropping column a would result in the new constraint that all values in column b be unique. In order to drop the column, an explicit DROP PRIMARY KEY and ADD PRIMARY KEY would be required. Up until MariaDB 10.2.7, the column was dropped and the additional constraint applied, resulting in the following structure: ALTER TABLE x DROP COLUMN a; Query OK, 0 rows affected (0.46 sec) DESC x; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | b | int(11) | NO | PRI | NULL | | +-------+---------+------+-----+---------+-------+ MariaDB 10.4.0 supports instant DROP COLUMN. DROP COLUMN of an indexed column would imply DROP INDEX (and in the case of a non-UNIQUE multi-column index, possibly ADD INDEX). These will not be allowed with ALGORITHM=INSTANT, but unlike before, they can be allowed with ALGORITHM=NOCOPY RESTRICT and CASCADE are allowed to make porting from other database systems easier. In MariaDB, they do nothing. MODIFY COLUMN Allows you to modify the type of a column. The column will be at the same place as the original column and all indexes on the column will be kept. Note that when modifying column, you should specify all attributes for the new column. CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY KEY((a)); ALTER TABLE t1 MODIFY a BIGINT UNSIGNED AUTO_INCREMENT; CHANGE COLUMN Works like MODIFY COLUMN except that you can also change the name of the column. The column will be at the same place as the original column and all index on the column will be kept. CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY KEY(a)); ALTER TABLE t1 CHANGE a b BIGINT UNSIGNED AUTO_INCREMENT; ALTER COLUMN This lets you change column options. CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, b varchar(50), PRIMARY KEY(a)); ALTER TABLE t1 ALTER b SET DEFAULT 'hello'; ADD PRIMARY KEY Add a primary key. For PRIMARY KEY indexes, you can specify a name for the index, but it is silently ignored, and the name of the index is always PRIMARY. See Getting Started with Indexes: Primary Key for more information. DROP PRIMARY KEY Drop a primary key. For PRIMARY KEY indexes, you can specify a name for the index, but it is silently ignored, and the name of the index is always PRIMARY. See Getting Started with Indexes: Primary Key for more information. ADD FOREIGN KEY Add a foreign key. For FOREIGN KEY indexes, a reference definition must be provided. For FOREIGN KEY indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages. First, you have to specify the name of the target (parent) table and a column or a column list which must be indexed and whose values must match to the foreign key's values. The MATCH clause is accepted to improve the compatibility with other DBMS's, but has no meaning in MariaDB. The ON DELETE and ON UPDATE clauses specify what must be done when a DELETE (or a REPLACE) statements attempts to delete a referenced row from the parent table, and when an UPDATE statement attempts to modify the referenced foreign key columns in a parent table row, respectively. The following options are allowed: RESTRICT: The delete/update operation is not performed. The statement terminates with a 1451 error (SQLSTATE '2300'). NO ACTION: Synonym for RESTRICT. CASCADE: The delete/update operation is performed in both tables. SET NULL: The update or delete goes ahead in the parent table, and the corresponding foreign key fields in the child table are set to NULL. (They must not be defined as NOT NULL for this to succeed). MariaDB until 5.3 SET DEFAULT: This option is currently implemented only for the PBXT storage engine, which is disabled by default and no longer maintained. It sets the child table's foreign key fields to their DEFAULT values when the referenced parent table key entries are updated or deleted. If either clause is omitted, the default behavior for the omitted clause is RESTRICT. See Foreign Keys for more information. DROP FOREIGN KEY Drop a foreign key. See Foreign Keys for more information. ADD INDEX Add a plain index. Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes. See Getting Started with Indexes: Plain Indexes for more information. DROP INDEX Drop a plain index. Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes. See Getting Started with Indexes: Plain Indexes for more information. ADD UNIQUE INDEX Add a unique index. The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index. For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages. See Getting Started with Indexes: Unique Index for more information. DROP UNIQUE INDEX Drop a unique index. The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index. For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages. See Getting Started with Indexes: Unique Index for more information. ADD FULLTEXT INDEX Add a FULLTEXT index. See Full-Text Indexes for more information. DROP FULLTEXT INDEX Drop a FULLTEXT index. See Full-Text Indexes for more information. ADD SPATIAL INDEX Add a SPATIAL index. See SPATIAL INDEX for more information. DROP SPATIAL INDEX Drop a SPATIAL index. See SPATIAL INDEX for more information. ENABLE/ DISABLE KEYS DISABLE KEYS will disable all non unique keys for the table for storage engines that support this (at least MyISAM and Aria). This can be used to speed up inserts into empty tables. ENABLE KEYS will enable all disabled keys. RENAME TO Renames the table. See also RENAME TABLE. ADD CONSTRAINT Modifies the table adding a constraint on a particular column or columns. MariaDB 10.2.1 introduced new ways to define a constraint. Note: Before MariaDB 10.2.1, constraint expressions were accepted in syntax, but ignored. ALTER TABLE table_name ADD CONSTRAINT [constraint_name] CHECK(expression); Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraint fails, then the row will not be updated. One can use most deterministic functions in a constraint, including UDF's. CREATE TABLE account_ledger ( id INT PRIMARY KEY AUTO_INCREMENT, transaction_name VARCHAR(100), credit_account VARCHAR(100), credit_amount INT, debit_account VARCHAR(100), debit_amount INT); ALTER TABLE account_ledger ADD CONSTRAINT is_balanced CHECK((debit_amount + credit_amount) = 0); The constraint_name is optional. If you don't provide one in the ALTER TABLE statement, MariaDB auto-generates a name for you. This is done so that you can remove it later using DROP CONSTRAINT clause. You can disable all constraint expression checks by setting the variable check_constraint_checks to OFF. You may find this useful when loading a table that violates some constraints that you want to later find and fix in SQL. To view constraints on a table, query information_schema.TABLE_CONSTRAINTS: SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE FROM information_schema.TABLE_CONSTRAINTS WHERE TABLE_NAME = 'account_ledger'; +-----------------+----------------+-----------------+ | CONSTRAINT_NAME | TABLE_NAME | CONSTRAINT_TYPE | +-----------------+----------------+-----------------+ | is_balanced | account_ledger | CHECK | +-----------------+----------------+-----------------+ DROP CONSTRAINT DROP CONSTRAINT for UNIQUE and FOREIGN KEY constraints was introduced in MariaDB 10.2.22 and MariaDB 10.w3.13. DROP CONSTRAINT for CHECK constraints was introduced in MariaDB 10.2.1 Modifies the table, removing the given constraint. ALTER TABLE table_name DROP CONSTRAINT constraint_name; When you add a constraint to a table, whether through a CREATE TABLE or ALTER TABLE...ADD CONSTRAINT statement, you can either set a constraint_name yourself, or allow MariaDB to auto-generate one for you. To view constraints on a table, query information_schema.TABLE_CONSTRAINTS. For instance, CREATE TABLE t ( a INT, b INT, c INT, CONSTRAINT CHECK(a > b), CONSTRAINT check_equals CHECK(a = c)); SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE FROM information_schema.TABLE_CONSTRAINTS WHERE TABLE_NAME = 't'; +-----------------+----------------+-----------------+ | CONSTRAINT_NAME | TABLE_NAME | CONSTRAINT_TYPE | +-----------------+----------------+-----------------+ | check_equals | t | CHECK | | CONSTRAINT_1 | t | CHECK | +-----------------+----------------+-----------------+ To remove a constraint from the table, issue an ALTER TABLE...DROP CONSTRAINT statement. For example, ALTER TABLE t DROP CONSTRAINT is_unique; ADD SYSTEM VERSIONING System-versioned tables was added in MariaDB 10.3.4. Add system versioning. DROP SYSTEM VERSIONING System-versioned tables was added in MariaDB 10.3.4. Drop system versioning. ADD PERIOD FOR SYSTEM_TIME System-versioned tables was added in MariaDB 10.3.4. FORCE ALTER TABLE ... FORCE can force MariaDB to re-build the table. In MariaDB 5.5 and before, this could only be done by setting the ENGINE table option to its old value. For example, for an InnoDB table, one could execute the following: ALTER TABLE tab_name ENGINE = InnoDB; In MariaDB 10.0 and later, the FORCE option can be used instead. For example, : ALTER TABLE tab_name FORCE; With InnoDB, the table rebuild will only reclaim unused space (i.e. the space previously used for deleted rows) if the innodb_file_per_table system variable is set to ON. If the system variable is OFF, then the space will not be reclaimed, but it will be-re-used for new data that's later added. EXCHANGE PARTITION ALTER TABLE ... EXCHANGE PARTITION was introduced in MariaDB 10.0.4 This is used to exchange the tablespace files between a partition and another table. See copying InnoDB's transportable tablespaces for more information. DISCARD TABLESPACE This is used to discard an InnoDB table's tablespace. See copying InnoDB's transportable tablespaces for more information. IMPORT TABLESPACE This is used to import an InnoDB table's tablespace. The tablespace should have been copied from its original server after executing FLUSH TABLES FOR EXPORT. See copying InnoDB's transportable tablespaces for more information. ALTER TABLE ... IMPORT only applies to InnoDB tables. Most other popular storage engines, such as Aria and MyISAM, will recognize their data files as soon as they've been placed in the proper directory under the datadir, and no special DDL is required to import them. ALGORITHM In MariaDB 5.5 and before, ALTER TABLE operations required making a temporary copy of the table, which can be slow for large tables. In MariaDB 10.0 and later, the ALTER TABLE statement supports the ALGORITHM clause. This clause is one of the clauses that is used to implement online DDL. ALTER TABLE supports several different algorithms. An algorithm can be explicitly chosen for an ALTER TABLE operation by setting the ALGORITHM clause. The supported values are: ALGORITHM=DEFAULT - This implies the default behavior for the specific statement, such as if no ALGORITHM clause is specified. ALGORITHM=COPY ALGORITHM=INPLACE ALGORITHM=NOCOPY - This was added in MariaDB 10.3.7. ALGORITHM=INSTANT - This was added in MariaDB 10.3.7. See InnoDB Online DDL Overview: ALGORITHM for information on how the ALGORITHM clause affects InnoDB. ALGORITHM=DEFAULT The default behavior, which occurs if ALGORITHM=DEFAULT is specified, or if ALGORITHM is not specified at all, usually only makes a copy if the operation doesn't support being done in-place at all. In this case, the most efficient available algorithm will usually be used. However, in MariaDB 10.3.6 and before, if the value of the old_alter_table system variable is set to ON, then the default behavior is to perform ALTER TABLE operations by making a copy of the table using the old algorithm. In MariaDB 10.3.7 and later, the old_alter_table system variable is deprecated. Instead, the alter_algorithm system variable defines the default algorithm for ALTER TABLE operations. ALGORITHM=COPY ALGORITHM=COPY was introduced in MariaDB 10.0 as the name for the original ALTER TABLE algorithm. When ALGORITHM=COPY is set, MariaDB essentially does the following operations: -- Create a temporary table with the new definition CREATE TEMPORARY TABLE tmp_tab ( ... ); -- Copy the data from the original table INSERT INTO tmp_tab SELECT * FROM original_tab; -- Drop the original table DROP TABLE original_tab; -- Rename the temporary table, so that it replaces the original one RENAME TABLE tmp_tab TO original_tab; This algorithm is very inefficient, but it is generic, so it works for all storage engines. If ALGORITHM=COPY is specified, then the copy algorithm will be used even if it is not necessary. This can result in a lengthy table copy. If multiple ALTER TABLE operations are required that each require the table to be rebuilt, then it is best to specify all operations in a single ALTER TABLE statement, so that the table is only rebuilt once. ALGORITHM=INPLACE ALGORITHM=INPLACE was introduced in MariaDB 10.0. ALGORITHM=COPY can be incredibly slow, because the whole table has to be copied and rebuilt. ALGORITHM=INPLACE was introduced as a way to avoid this by performing operations in-place and avoiding the table copy and rebuild, when possible. When ALGORITHM=INPLACE is set, the underlying storage engine uses optimizations to perform the operation while avoiding the table copy and rebuild. However, INPLACE is a bit of a misnomer, since some operations may still require the table to be rebuilt for some storage engines. Regardless, several operations can be performed without a full copy of the table for some storage engines. A more accurate name would have been ALGORITHM=ENGINE, where ENGINE refers to an "engine-specific" algorithm. If an ALTER TABLE operation supports ALGORITHM=INPLACE, then it can be performed using optimizations by the underlying storage engine, but it may rebuilt. See InnoDB Online DDL Operations with ALGORITHM=INPLACE for more. ALGORITHM=NOCOPY ALGORITHM=NOCOPY was introduced in MariaDB 10.3.7. ALGORITHM=INPLACE can sometimes be surprisingly slow in instances where it has to rebuild the clustered index, because when the clustered index has to be rebuilt, the whole table has to be rebuilt. ALGORITHM=NOCOPY was introduced as a way to avoid this. If an ALTER TABLE operation supports ALGORITHM=NOCOPY, then it can be performed without rebuilding the clustered index. If ALGORITHM=NOCOPY is specified for an ALTER TABLE operation that does not support ALGORITHM=NOCOPY, then an error will be raised. In this case, raising an error is preferable, if the alternative is for the operation to rebuild the clustered index, and perform unexpectedly slowly. See InnoDB Online DDL Operations with ALGORITHM=NOCOPY for more. ALGORITHM=INSTANT ALGORITHM=INSTANT was introduced in MariaDB 10.3.7. ALGORITHM=INPLACE can sometimes be surprisingly slow in instances where it has to modify data files. ALGORITHM=INSTANT was introduced as a way to avoid this. If an ALTER TABLE operation supports ALGORITHM=INSTANT, then it can be performed without modifying any data files. If ALGORITHM=INSTANT is specified for an ALTER TABLE operation that does not support ALGORITHM=INSTANT, then an error will be raised. In this case, raising an error is preferable, if the alternative is for the operation to modify data files, and perform unexpectedly slowly. See InnoDB Online DDL Operations with ALGORITHM=INSTANT for more. LOCK In MariaDB 10.0 and later, the ALTER :kN TABLE statement supports the LOCK clause. This clause is one of the clauses that is used to implement online DDL. ALTER TABLE supports several different locking strategies. A locking strategy can be explicitly chosen for an ALTER TABLE operation by setting the LOCK clause. The supported values are: DEFAULT: Acquire the least restrictive lock on the table that is supported for the specific operation. Permit the maximum amount of concurrency that is supported for the specific operation. NONE: Acquire no lock on the table. Permit all concurrent DML. If this locking strategy is not permitted for an operation, then an error is raised. SHARED: Acquire a read lock on the table. Permit read-only concurrent DML. If this locking strategy is not permitted for an operation, then an error is raised. EXCLUSIVE: Acquire a write lock on the table. Do not permit concurrent DML. Different storage engines support different locking strategies for different operations. If a specific locking strategy is chosen for an ALTER TABLE operation, and that table's storage engine does not support that locking strategy for that specific operation, then an error will be raised. If the LOCK clause is not explicitly set, then the operation uses LOCK=DEFAULT. ALTER ONLINE TABLE is equivalent to LOCK=NONE. Therefore, the ALTER ONLINE TABLE statement can be used to ensure that your ALTER TABLE operation allows all concurrent DML. See InnoDB Online DDL Overview: LOCK for information on how the LOCK clause affects InnoDB. Progress Reporting MariaDB provides progress reporting for ALTER TABLE statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this:: ALTER TABLE test ENGINE=Aria; Stage: 1 of 2 'copy to tmp table' 46% of stage The progress report is also shown in the output of the SHOW PROCESSLIST statement and in the contents of the information_schema.PROCESSLIST table. See Progress Reporting for more information. Aborting ALTER TABLE Operations If an ALTER TABLE operation is being performed and the connection is killed, the changes will be rolled back in a controlled manner. The rollback can be a slow operation as the time it takes is relative to how far the operation has progressed. Aborting ALTER TABLE ... ALGORITHM=COPY was made faster by removing excessive undo logging (MDEV-11415). This significantly shortens the time it takes to abort a running ALTER TABLE operation. Examples -------- Adding a new column: ALTER TABLE t1 ADD x INT; Dropping a column: ALTER TABLE t1 DROP x; Modifying the type of a column: ALTER TABLE t1 MODIFY x bigint unsigned; Changing the name and type of a column: ALTER TABLE t1 CHANGE a b bigint unsigned auto_increment; Combining multiple clauses in a single ALTER TABLE statement, separated by commas: ALTER TABLE t1 DROP x, ADD x2 INT, CHANGE y y2 INT; Changing the storage engine: ALTER TABLE t1 ENGINE = InnoDB; Rebuilding the table (the previous example will also rebuild the table if it was already InnoDB): ALTER TABLE t1 FORCE; URL: https://mariadb.com/kb/en/alter-table/is function, the subselect will execute with your privileges. As long as you have privileges to select the salary of each employee, the caller of the function will be able to get the maximum salary for each department without being able to see individual salaries. Character sets and collations Function return types can be declared to use any valid character set and collation. If used, the COLLATE attribute needs to be preceded by a CHARACTER SET attribute. If the character set and collation are not specifically set in the statement, the database defaults at the time of creation will be used. If the database defaults change at a later stage, the stored function character set/collation will not be changed at the same time; the stored function needs to be dropped and recreated to ensure the same character set/collation as the database is used. Examples -------- The following example function takes a parameter, performs an operation using an SQL function, and returns the result. CREATE FUNCTION hello (s CHAR(20)) RETURNS CHAR(50) DETERMINISTIC RETURN CONCAT('Hello, ',s,'!'); SELECT hello('world'); +----------------+ | hello('world') | +----------------+ | Hello, world! | +----------------+ You can use a compound statement in a function to manipulate data with statements like INSERT and UPDATE. The following example creates a counter function that uses a temporary table to store the current value. Because the compound statement contains statements terminated with semicolons, you have to first change the statement delimiter with the DELIMITER statement to allow the semicolon to be used in the function body. See Delimiters in the mysql client for more. CREATE TEMPORARY TABLE counter (c INT); INSERT INTO counter VALUES (0); DELIMITER // CREATE FUNCTION counter () RETURNS INT BEGIN UPDATE counter SET c = c + 1; RETURN (SELECT c FROM counter LIMIT 1); END // DELIMITER ; Character set and collation: CREATE FUNCTION hello2 (s CHAR(20)) RETURNS CHAR(50) CHARACTER SET 'utf8' COLLATE 'utf8_bin' DETERMINISTIC RETURN CONCAT('Hello, ',s,'!'); URL: https://mariadb.com/kb/en/create-function/x _ l tU  %'CONSTRAINTMariaDB supports the implementation of constraints at the table-level using either CREATE TABLE or ALTER TABLE statements. A table constraint restricts the data you can add to the table. If you attempt to insert invalid data on a column, MariaDB throws an error. Syntax ------ [CONSTRAINT [symbol]] constraint_expression constraint_expression: | PRIMARY KEY [index_type] (index_col_name, ...) [index_option] ... | FOREIGN KEY [index_name] (index_col_name, ...) REFERENCES tbl_name (index_col_name, ...) [ON DELETE reference_option] [ON UPDATE reference_option] | UNIQUE [INDEX|KEY] [index_name] [index_type] (index_col_name, ...) [index_option] ... | CHECK (check_constraints) index_type: USING {BTREE | HASH | RTREE} index_col_name: col_name [(length)] [ASC | DESC] index_option: | KEY_BLOCK_SIZE [=] value | index_type | WITH PARSER parser_name | COMMENT 'string' | CLUSTERING={YES|NO} reference_option: RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT Description ----------- Constraints provide restrictions on the data you can add to a table. This allows you to enforce data integrity from MariaDB, rather than through application logic. When a statement violates a constraint, MariaDB throws an error. There are four types of table constraints: Constraint | Description | PRIMARY KEY | Sets the column for referencing rows. Values must be unique and not null. | FOREIGN KEY | Sets the column to reference the primary key on another table. | UNIQUE | Requires values in column or columns only occur once in the table. | CHECK | Checks whether the data meets the given condition. | FOREIGN KEY Constraints InnoDB supports foreign key constraints. The syntax for a foreign key constraint definition in InnoDB looks like this: [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name, ...) REFERENCES tbl_name (index_col_name,...) [ON DELETE reference_option] [ON UPDATE reference_option] reference_option: RESTRICT | CASCADE | SET NULL | NO ACTION CHECK Constraints From MariaDB 10.2.1, constraints are enforced. Before MariaDB 10.2.1 constraint expressions were accepted in the syntax but ignored. In MariaDB 10.2.1 you can define constraints in 2 different ways: CHECK(expression) given as part of a column definition. CONSTRAINT [constraint_name] CHECK (expression) Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraint expression returns false, then the row will not be inserted or updated. One can use most deterministic functions in a constraint, including UDFs. CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2), CONSTRAINT a_greater CHECK (a>b)); If you use the second format and you don't give a name to the constraint, then the constraint will get an automatically generated name. This is done so that you can later delete the constraint with ALTER TABLE DROP constraint_name. One can disable all constraint expression checks by setting the check_constraint_checks variable to OFF. This is useful for example when loading a table that violates some constraints that you want to later find and fix in SQL. Replication In row-based replication, only the master checks constraints, and failed statements will not be replicated. In statement-based replication, the slaves will also check constraints. Constraints should therefore be identical, as well as deterministic, in a replication environment. Auto_increment From MariaDB 10.2.6, auto_increment columns are no longer permitted in check constraints. Previously they were permitted, but would not work correctly. See MDEV-11117. Examples -------- CREATE TABLE product (category INT NOT NULL, id INT NOT NULL, price DECIMAL, PRIMARY KEY(category, id)) ENGINE=INNODB; CREATE TABLE customer (id INT NOT NULL, PRIMARY KEY (id)) ENGINE=INNODB; CREATE TABLE product_order (no INT NOT NULL AUTO_INCREMENT, product_category INT NOT NULL, product_id INT NOT NULL, customer_id INT NOT NULL, PRIMARY KEY(no), INDEX (product_category, product_id), FOREIGN KEY (product_category, product_id) REFERENCES product(category, id) ON UPDATE CASCADE ON DELETE RESTRICT, INDEX (customer_id), FOREIGN KEY (customer_id) REFERENCES customer(id)) ENGINE=INNODB; The following examples will work from MariaDB 10.2.1 onwards. Numeric constraints and comparisons: CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2), CONSTRAINT a_greater CHECK (a>b)); INSERT INTO t1(a) VALUES (1); ERROR 4022 (23000): CONSTRAINT `a` failed for `test`.`t1` INSERT INTO t1(a,b) VALUES (3,4); ERROR 4022 (23000): CONSTRAINT `a_greater` failed for `test`.`t1` INSERT INTO t1(a,b) VALUES (4,3); Query OK, 1 row affected (0.04 sec) Dropping a constraint: ALTER TABLE t1 DROP CONSTRAINT a_greater; Adding a constraint: ALTER TABLE t1 ADD CONSTRAINT a_greater CHECK (a>b); Date comparisons and character length: CREATE TABLE t2 (name VARCHAR(30) CHECK (CHAR_LENGTH(name)>2), start_date DATE, end_date DATE CHECK (start_date IS NULL OR end_date IS NULL OR start_date2)), start_date DATE, end_date DATE CHECK (start_date IS NULL OR end_date IS NULL OR start_date2 is very different to CHAR_LENGTH(name>2) as the latter mistakenly performs a numeric comparison on the name field, leading to unexpected results. URL: https://mariadb.com/kb/en/constraint/https://mariadb.com/kb/en/constraint/ B{@3 x''CREATE EVENTSyntax ------ CREATE [OR REPLACE] [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }] EVENT [IF NOT EXISTS] event_name ON SCHEDULE schedule [ON COMPLETION [NOT] PRESERVE] [ENABLE | DISABLE | DISABLE ON SLAVE] [COMMENT 'comment'] DO sql_statement; schedule: AT timestamp [+ INTERVAL interval] ... | EVERY interval [STARTS timestamp [+ INTERVAL interval] ...] [ENDS timestamp [+ INTERVAL interval] ...] interval: quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE | WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE | DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND} Description ----------- This statement creates and schedules a new event. It requires the EVENT privilege for the schema in which the event is to be created. The minimum requirements for a valid CREATE EVENT statement are as follows: The keywords CREATE EVENT plus an event name, which uniquely identifies the event in the current schema. (Prior to MySQL 5.1.12, the event name needed to be unique only among events created by the same user on a given database.) An ON SCHEDULE clause, which determines when and how often the event executes. A DO clause, which contains the SQL statement to be executed by an event. Here is an example of a minimal CREATE EVENT statement: CREATE EVENT myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR DO UPDATE myschema.mytable SET mycol = mycol + 1; The previous statement creates an event named myevent. This event executes once — one hour following its creation — by running an SQL statement that increments the value of the myschema.mytable table's mycol column by 1. The event_name must be a valid MariaDB identifier with a maximum length of 64 characters. It may be delimited using back ticks, and may be qualified with the name of a database schema. An event is associated with both a MariaDB user (the definer) and a schema, and its name must be unique among names of events within that schema. In general, the rules governing event names are the same as those for names of stored routines. See Identifier Names. If no schema is indicated as part of event_name, the default (current) schema is assumed. For valid identifiers to use as event names, see Identifier Names. OR REPLACE The OR REPLACE clause was included in MariaDB 10.1.4. If used and the event already exists, instead of an error being returned, the existing event will be dropped and replaced by the newly defined event. IF NOT EXISTS If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the event already exists. Cannot be used together with OR REPLACE. ON SCHEDULE The ON SCHEDULE clause can be used to specify when the event must be triggered. AT If you want to execute the event only once (one time event), you can use the AT keyword, followed by a timestamp. If you use CURRENT_TIMESTAMP, the event acts as soon as it is created. As a convenience, you can add one or more intervals to that timestamp. You can also specify a timestamp in the past, so that the event is stored but not triggered, until you modify it via ALTER EVENT. The following example shows how to create an event that will be triggered tomorrow at a certain time: CREATE EVENT example ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR DO something; You can also specify that an event must be triggered at a regular interval (recurring event). In such cases, use the EVERY clause followed by the interval. If an event is recurring, you can specify when the first execution must happen via the STARTS clause and a maximum time for the last execution via the ENDS clause. STARTS and ENDS clauses are followed by a timestamp and, optionally, one or more intervals. The ENDS clause can specify a timestamp in the past, so that the event is stored but not executed until you modify it via ALTER EVENT. In the following example, next month a recurring event will be triggered hourly for a week: CREATE EVENT example ON SCHEDULE EVERY 1 HOUR STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK DO some_task; Intervals consist of a quantity and a time unit. The time units are the same used for other staments and time functions, except that you can't use microseconds for events. For simple time units, like HOUR or MINUTE, the quantity is an integer number, for example '10 MINUTE'. For composite time units, like HOUR_MINUTE or HOUR_SECOND, the quantity must be a string with all involved simple values and their separators, for example '2:30' or '2:30:30'. ON COMPLETION [NOT] PRESERVE The ON COMPLETION clause can be used to specify if the event must be deleted after its last execution (that is, after its AT or ENDS timestamp is past). By default, events are dropped when they are expired. To explicitly state that this is the desired behaviour, you can use ON COMPLETION NOT PRESERVE. Instead, if you want the event to be preserved, you can use ON COMPLETION PRESERVE. In you specify ON COMPLETION NOT PRESERVE, and you specify a timestamp in the past for AT or ENDS clause, the event will be immediatly dropped. In such cases, you will get a Note 1558: "Event execution time is in the past and ON COMPLETION NOT PRESERVE is set. The event was dropped immediately after creation". ENABLE/DISABLE/DISABLE ON SLAVE Events are ENABLEd by default. If you want to stop MariaDB from executing an event, you may specify DISABLE. When it is ready to be activated, you may enable it using ALTER EVENT. Another option is DISABLE ON SLAVE, which indicates that an event was created on a master and has been replicated to the slave, which is prevented from executing the event. If DISABLE ON SLAVE is specifically set, the event will not be executed. COMMENT The COMMENT clause may be used to set a comment for the event. Maximum length for comments is 64 characters. The comment is a string, so it must be quoted. To see events comments, you can query the INFORMATION_SCHEMA.EVENTS table (the column is named EVENT_COMMENT). Examples -------- Minimal CREATE EVENT statement: CREATE EVENT myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR DO UPDATE myschema.mytable SET mycol = mycol + 1; An event that will be triggered tomorrow at a certain time: CREATE EVENT example ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR DO something; Next month a recurring event will be triggered hourly for a week: CREATE EVENT example ON SCHEDULE EVERY 1 HOUR STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK DO some_task; OR REPLACE and IF NOT EXISTS: CREATE EVENT myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR DO UPDATE myschema.mytable SET mycol = mycol + 1; ERROR 1537 (HY000): Event 'myevent' already exists CREATE OR REPLACE EVENT myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR DO UPDATE myschema.mytable SET mycol = mycol + 1;; Query OK, 0 rows affected (0.00 sec) CREATE EVENT IF NOT EXISTS myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR DO UPDATE myschema.mytable SET mycol = mycol + 1; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+--------------------------------+ | Level | Code | Message | +-------+------+--------------------------------+ | Note | 1537 | Event 'myevent' already exists | +-------+------+--------------------------------+ URL: https://mariadb.com/kb/en/create-event/https://mariadb.com/kb/en/create-event/ oupSyntax ------ CREATE [OR REPLACE] [DEFINER = {user | CURRENT_USER | role | CURRENT_ROLE }] [AGGREGATE] FUNCTION [IF NOT EXISTS] func_name ([func_parameter[,...]]) RETURNS type [characteristic ...] RETURN func_body func_parameter: param_name type type: Any valid MariaDB data type characteristic: LANGUAGE SQL | [NOT] DETERMINISTIC | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string' func_body: Valid SQL procedure statement Description ----------- Use the CREATE FUNCTION statement to create a new stored function. You must have the CREATE ROUTINE database privilege to use CREATE FUNCTION. A function takes any number of arguments and returns a value from the function body. The function body can be any valid SQL expression as you would use, for example, in any select expression. If you have the appropriate privileges, you can call the function exactly as you would any built-in function. See Security below for details on privileges. You can also use a variant of the CREATE FUNCTION statement to install a user-defined function (UDF) defined by a plugin. See CREATE FUNCTION (UDF) for details. You can use a SELECT statement for the function body by enclosing it in parentheses, exactly as you would to use a subselect for any other expression. The SELECT statement must return a single value. If more than one column is returned when the function is called, error 1241 results. If more than one row is returned when the function is called, error 1242 results. Use a LIMIT clause to ensure only one row is returned. You can also replace the RETURN clause with a BEGIN...END compound statement. The compound statement must contain a RETURN statement. When the function is called, the RETURN statement immediately returns its result, and any statements after RETURN are effectively ignored. By default, a function is associated with the default database. To associate the function explicitly with a given database, specify the fully-qualified name as db_name.func_name when you create it. If the function name is the same as the name of a built-in function, you must use the fully qualified name when you call it. The parameter list enclosed within parentheses must always be present. If there are no parameters, an empty parameter list of () should be used. Parameter names are not case sensitive. Each parameter can be declared to use any valid data type, except that the COLLATE attribute cannot be used. For valid identifiers to use as function names, see Identifier Names. AGGREGATE From MariaDB 10.3.3, it is possible to create stored aggregate functions as well. See Stored Aggregate Functions for details. RETURNS The RETURNS clause specifies the return type of the function. NULL values are permitted with all return types. What happens if the RETURN clause returns a value of a different type? It depends on the SQL_MODE in effect at the moment of the function creation. If the SQL_MODE is strict (STRICT_ALL_TABLES or STRICT_TRANS_TABLES flags are specified), a 1366 error will be produced. Otherwise, the value is coerced to the proper type. For example, if a function specifies an ENUM or SET value in the RETURNS clause, but the RETURN clause returns an integer, the value returned from the function is the string for the corresponding ENUM member of set of SET members. MariaDB stores the SQL_MODE system variable setting that is in effect at the time a routine is created, and always executes the routine with this setting in force, regardless of the server SQL mode in effect when the routine is invoked. LANGUAGE SQL LANGUAGE SQL is a standard SQL clause, and it can be used in MariaDB for portability. However that clause has no meaning, because SQL is the only supported language for stored functions. A function is deterministic if it can produce only one result for a given list of parameters. If the result may be affected by stored data, server variables, random numbers or any value that is not explicitly passed, then the function is not deterministic. Also, a function is non-deterministic if it uses non-deterministic functions like NOW() or CURRENT_TIMESTAMP(). The optimizer may choose a faster execution plan if it known that the function is deterministic. In such cases, you should declare the routine using the DETERMINISTIC keyword. If you want to explicitly state that the function is not deterministic (which is the default) you can use the NOT DETERMINISTIC keywords. If you declare a non-deterministic function as DETERMINISTIC, you may get incorrect results. If you declare a deterministic function as NOT DETERMINISTIC, in some cases the queries will be slower. OR REPLACE If the optional OR REPLACE clause is used, it acts as a shortcut for: DROP FUNCTION IF EXISTS function_name; CREATE FUNCTION function_name ...; with the exception that any existing privileges for the function are not dropped. IF NOT EXISTS If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the function already exists. Cannot be used together with OR REPLACE. [NOT] DETERMINISTIC The [NOT] DETERMINISTIC clause also affects binary logging, because the STATEMENT format can not be used to store or replicate non-deterministic statements. CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA are informative clauses that tell the server what the function does. MariaDB does not check in any way whether the specified clause is correct. If none of these clauses are specified, CONTAINS SQL is used by default. MODIFIES SQL DATA MODIFIES SQL DATA means that the function contains statements that may modify data stored in databases. This happens if the function contains statements like DELETE, UPDATE, INSERT, REPLACE or DDL. READS SQL DATA READS SQL DATA means that the function reads data stored in databases, but does not modify any data. This happens if SELECT statements are used, but there no write operations are executed. CONTAINS SQL CONTAINS SQL means that the function contains at least one SQL statement, but it does not read or write any data stored in a database. Examples include SET or DO. NO SQL NO SQL means nothing, because MariaDB does not currently support any language other than SQL. Oracle Mode From MariaDB 10.3, a subset of Oracle's PL/SQL language has been supported in addition to the traditional SQL/PSM-based MariaDB syntax. See Oracle mode from MariaDB 10.3 for details on changes when running Oracle mode. Security You must have the EXECUTE privilege on a function to call it. MariaDB automatically grants the EXECUTE and ALTER ROUTINE privileges to the account that called CREATE FUNCTION, even if the DEFINER clause was used. Each function has an account associated as the definer. By default, the definer is the account that created the function. Use the DEFINER clause to specify a different account as the definer. You must have the SUPER privilege to use the DEFINER clause. See Account Names for details on specifying accounts. The SQL SECURITY clause specifies what privileges are used when a function is called. If SQL SECURITY is INVOKER, the function body will be evaluated using the privileges of the user calling the function. If SQL SECURITY is DEFINER, the function body is always evaluated using the privileges of the definer account. DEFINER is the default. This allows you to create functions that grant limited access to certain data. For example, say you have a table that stores some employee information, and that you've granted SELECT privileges only on certain columns to the user account roger. CREATE TABLE employees (name TINYTEXT, dept TINYTEXT, salary INT); GRANT SELECT (name, dept) ON employees TO roger; To allow the user the get the maximum salary for a department, define a function and grant the EXECUTE privilege: CREATE FUNCTION max_salary (dept TINYTEXT) RETURNS INT RETURN (SELECT MAX(salary) FROM employees WHERE employees.dept = dept); GRANT EXECUTE ON FUNCTION max_salary TO roger; Since SQL SECURITY defaults to DEFINER, whenever the user roger calls thJ ''CREATE INDEXSyntax ------ CREATE [OR REPLACE] [UNIQUE|FULLTEXT|SPATIAL] INDEX [IF NOT EXISTS] index_name [index_type] ON tbl_name (index_col_name,...) [WAIT n | NOWAIT] [index_option] [algorithm_option | lock_option] ... index_col_name: col_name [(length)] [ASC | DESC] index_type: USING {BTREE | HASH | RTREE} index_option: KEY_BLOCK_SIZE [=] value | index_type | WITH PARSER parser_name | COMMENT 'string' algorithm_option: ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT} lock_option: LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE} Description ----------- CREATE INDEX is mapped to an ALTER TABLE statement to create indexes. See ALTER TABLE. CREATE INDEX cannot be used to create a PRIMARY KEY; use ALTER TABLE instead. If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables. Another shortcut, DROP INDEX, allows the removal of an index. For valid identifiers to use as index names, see Identifier Names. Note that KEY_BLOCK_SIZE is currently ignored in CREATE INDEX, although it is included in the output of SHOW CREATE TABLE. Privileges Executing the CREATE INDEX statement requires the INDEX privilege for the table or the database. Online DDL In MariaDB 10.0 and later, online DDL is supported with the ALGORITHM and LOCK clauses. See InnoDB Online DDL Overview for more information on online DDL with InnoDB. CREATE OR REPLACE INDEX ... The OR REPLACE clause was added in MariaDB 10.1.4. If the OR REPLACE clause is used and if the index already exists, then instead of returning an error, the server will drop the existing index and replace it with the newly defined index. CREATE INDEX IF NOT EXISTS ... If the IF NOT EXISTS clause is used, then the index will only be created if an index with the same name does not already exist. If the index already exists, then a warning will be triggered by default. Index Definitions See CREATE TABLE: Index Definitions for information about index definitions. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. ALGORITHM See ALTER TABLE: ALGORITHM for more information. LOCK See ALTER TABLE: LOCK for more information. Progress Reporting MariaDB provides progress reporting for CREATE INDEX statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this:: CREATE INDEX ON tab (num);; Stage: 1 of 2 'copy to tmp table' 46% of stage The progress report is also shown in the output of the SHOW PROCESSLIST statement and in the contents of the information_schema.PROCESSLIST table. See Progress Reporting for more information. Examples -------- Creating a unique index: CREATE UNIQUE INDEX HomePhone ON Employees(Home_Phone); OR REPLACE and IF NOT EXISTS: CREATE INDEX xi ON xx5 (x); Query OK, 0 rows affected (0.03 sec) CREATE INDEX xi ON xx5 (x); ERROR 1061 (42000): Duplicate key name 'xi' CREATE OR REPLACE INDEX xi ON xx5 (x); Query OK, 0 rows affected (0.03 sec) CREATE INDEX IF NOT EXISTS xi ON xx5 (x); Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+-------------------------+ | Level | Code | Message | +-------+------+-------------------------+ | Note | 1061 | Duplicate key name 'xi' | +-------+------+-------------------------+ URL: https://mariadb.com/kb/en/create-index/https://mariadb.com/kb/en/create-index/x *'CREATE SEQUENCECREATE SEQUENCE was introduced in MariaDB 10.3. Syntax ------ CREATE [OR REPLACE] [TEMPORARY] SEQUENCE [IF NOT EXISTS] sequence_name [ INCREMENT [ BY | = ] increment ] [ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ] [ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ] [ START [ WITH | = ] start ] [ CACHE [=] cache | NOCACHE ] [ CYCLE | NOCYCLE] [table_options] The options for CREATE SEQUENCE can be given in any order, optionally followed by table_options. table_options can be any of the normal table options in CREATE TABLE but the most usable ones are ENGINE=... and COMMENT=. NOMAXVALUE and NOMINVALUE are there to allow one to create SEQUENCEs using the Oracle syntax. Description ----------- CREATE SEQUENCE will create a sequence that generates new values when called with NEXT VALUE FOR sequence_name. It's an alternative to AUTO INCREMENT when one wants to have more control of how the numbers are generated. As the SEQUENCE caches values (up to CACHE) it can in some cases be much faster than AUTO INCREMENT. Another benefit is that one can access the last value generated by all used sequences, which solves one of the limitations with LAST_INSERT_ID(). CREATE SEQUENCE requires the CREATE privilege. DROP SEQUENCE can be used to drop a sequence, and ALTER SEQUENCE to change it. Arguments to Create The following options may be used: Option | Default value |  Description | INCREMENT |  1 | Increment to use for values. May be negative. Setting an increment of 0 causes the sequence to use the value of the auto_increment_increment system variable at the time of creation, which is always a positive number. (see MDEV-16035). | MINVALUE | 1 if INCREMENT > 0 and -9223372036854775807 if INCREMENT < 0 | Minimum value for the sequence | MAXVALUE | 9223372036854775806 if INCREMENT > 0 and -1 if INCREMENT < 0 | Max value for sequence | START | MINVALUE if INCREMENT > 0 and MAX_VALUE if INCREMENT< 0 | First value that the sequence will generate | CACHE | 1000 |  Number of values that should be cached. 0 if no CACHE. The underlying table will be updated first time a new sequence number is generated and each time the cache runs out. | If CYCLE is used then the sequence should start again from MINVALUE after it has run out of values. Default value is NOCYCLE. Constraints on Create Arguments To be able to create a legal sequence, the following must hold: MAXVALUE >= start MAXVALUE > MINVALUE START >= MINVALUE MAXVALUE = -9223372036854775807 (LONGLONG_MIN+1) Note that sequences can't generate the maximum/minimum 64 bit number because of the constraint of MINVALUE and MAXVALUE. Examples -------- CREATE SEQUENCE s START WITH 100 INCREMENT BY 10; CREATE SEQUENCE s2 START WITH -100 INCREMENT BY -10; The following statement fails, as the increment conflicts with the defaults CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10; ERROR 4082 (HY000): Sequence 'test.s3' values are conflicting The sequence can be created by specifying workable minimum and maximum values: CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10 MINVALUE=-100 MAXVALUE=1000; URL: https://mariadb.com/kb/en/create-sequence/https://mariadb.com/kb/en/create-sequence/ Y4 +.'CREATE PACKAGE BODYOracle-style packages were introduced in MariaDB 10.3.5. Syntax ------ CREATE [ OR REPLACE ] [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }] PACKAGE BODY [ IF NOT EXISTS ] [ db_name . ] package_name [ package_characteristic... ] { AS | IS } package_implementation_declare_section package_implementation_executable_section END [ package_name] package_implementation_declare_section: package_implementation_item_declaration [ package_implementation_item_declaration... ] [ package_implementation_routine_definition... ] | package_implementation_routine_definition [ package_implementation_routine_definition...] package_implementation_item_declaration: variable_declaration ; variable_declaration: variable_name[,...] type [:= expr ] package_implementation_routine_definition: FUNCTION package_specification_function [ package_implementation_function_body ] ; | PROCEDURE package_specification_procedure [ package_implementation_procedure_body ] ; package_implementation_function_body: { AS | IS } package_routine_body [func_name] package_implementation_procedure_body: { AS | IS } package_routine_body [proc_name] package_routine_body: [ package_routine_declarations ] BEGIN statements [ EXCEPTION exception_handlers ] END package_routine_declarations: package_routine_declaration ';' [package_routine_declaration ';']... package_routine_declaration: variable_declaration | condition_name CONDITION FOR condition_value | user_exception_name EXCEPTION | CURSOR_SYM cursor_name [ ( cursor_formal_parameters ) ] IS select_statement ; package_implementation_executable_section: END | BEGIN statement ; [statement ; ]... [EXCEPTION exception_handlers] END exception_handlers: exception_handler [exception_handler...] exception_handler: WHEN_SYM condition_value [, condition_value]... THEN_SYM statement ; [statement ;]... condition_value: condition_name | user_exception_name | SQLWARNING | SQLEXCEPTION | NOT FOUND | OTHERS_SYM | SQLSTATE [VALUE] sqlstate_value | mariadb_error_code Description ----------- The CREATE PACKAGE BODY statement can be used when Oracle SQL_MODE is set. The CREATE PACKAGE BODY statement creates the package body for a stored package. The package specification must be previously created using the CREATE PACKAGE statement. A package body provides implementations of the package public routines and can optionally have: package-wide private variables package private routines forward declarations for private routines an executable initialization section Examples -------- SET sql_mode=ORACLE; DELIMITER $$ CREATE OR REPLACE PACKAGE employee_tools AS FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2); PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)); PROCEDURE raiseSalaryStd(eid INT); PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)); END; $$ CREATE PACKAGE BODY employee_tools AS -- package body variables stdRaiseAmount DECIMAL(10,2):=500; -- private routines PROCEDURE log (eid INT, ecmnt TEXT) AS BEGIN INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt); END; -- public routines PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS eid INT; BEGIN INSERT INTO employee (name, salary) VALUES (ename, esalary); eid:= last_insert_id(); log(eid, 'hire ' || ename); END; FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS nSalary DECIMAL(10,2); BEGIN SELECT salary INTO nSalary FROM employee WHERE id=eid; log(eid, 'getSalary id=' || eid || ' salary=' || nSalary); RETURN nSalary; END; PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS BEGIN UPDATE employee SET salary=salary+amount WHERE id=eid; log(eid, 'raiseSalary id=' || eid || ' amount=' || amount); END; PROCEDURE raiseSalaryStd(eid INT) AS BEGIN raiseSalary(eid, stdRaiseAmount); log(eid, 'raiseSalaryStd id=' || eid); END; BEGIN -- This code is executed when the current session -- accesses any of the package routines for the first time log(0, 'Session ' || connection_id() || ' ' || current_user || ' started'); END; $$ DELIMITER ; URL: https://mariadb.com/kb/en/create-package-body/https://mariadb.com/kb/en/create-package-body/ ('DROP DATABASESyntax ------ DROP {DATABASE | SCHEMA} [IF EXISTS] db_name Description ----------- DROP DATABASE drops all tables in the database and deletes the database. Be very careful with this statement! To use DROP DATABASE, you need the DROP privilege on the database. DROP SCHEMA is a synonym for DROP DATABASE. Important: When a database is dropped, user privileges on the database are not automatically dropped. See GRANT. IF EXISTS Use IF EXISTS to prevent an error from occurring for databases that do not exist. A NOTE is generated for each non-existent database when using IF EXISTS. See SHOW WARNINGS. Examples -------- DROP DATABASE bufg; Query OK, 0 rows affected (0.39 sec) DROP DATABASE bufg; ERROR 1008 (HY000): Can't drop database 'bufg'; database doesn't exist \W Show warnings enabled. DROP DATABASE IF EXISTS bufg; Query OK, 0 rows affected, 1 warning (0.00 sec) Note (Code 1008): Can't drop database 'bufg'; database doesn't exist URL: https://mariadb.com/kb/en/drop-database/https://mariadb.com/kb/en/drop-database/: z?gSyntax ------ CREATE [OR REPLACE] [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }] PROCEDURE sp_name ([proc_parameter[,...]]) [characteristic ...] routine_body proc_parameter: [ IN | OUT | INOUT ] param_name type type: Any valid MariaDB data type characteristic: LANGUAGE SQL | [NOT] DETERMINISTIC | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string' routine_body: Valid SQL procedure statement Description ----------- Creates a stored procedure. By default, a routine is associated with the default database. To associate the routine explicitly with a given database, specify the name as db_name.sp_name when you create it. When the routine is invoked, an implicit USE db_name is performed (and undone when the routine terminates). The causes the routine to have the given default database while it executes. USE statements within stored routines are disallowed. When a stored procedure has been created, you invoke it by using the CALL statement (see CALL). To execute the CREATE PROCEDURE statement, it is necessary to have the CREATE ROUTINE privilege. By default, MariaDB automatically grants the ALTER ROUTINE and EXECUTE privileges to the routine creator. See also Stored Routine Privileges. The DEFINER and SQL SECURITY clauses specify the security context to be used when checking access privileges at routine execution time, as described later. If the routine name is the same as the name of a built-in SQL function, you must use a space between the name and the following parenthesis when defining the routine, or a syntax error occurs. This is also true when you invoke the routine later. For this reason, we suggest that it is better to avoid re-using the names of existing SQL functions for your own stored routines. The IGNORE_SPACE SQL mode applies to built-in functions, not to stored routines. It is always allowable to have spaces after a routine name, regardless of whether IGNORE_SPACE is enabled. The parameter list enclosed within parentheses must always be present. If there are no parameters, an empty parameter list of () should be used. Parameter names are not case sensitive. Each parameter can be declared to use any valid data type, except that the COLLATE attribute cannot be used. For valid identifiers to use as procedure names, see Identifier Names. IN/OUT/INOUT Each parameter is an IN parameter by default. To specify otherwise for a parameter, use the keyword OUT or INOUT before the parameter name. An IN parameter passes a value into a procedure. The procedure might modify the value, but the modification is not visible to the caller when the procedure returns. An OUT parameter passes a value from the procedure back to the caller. Its initial value is NULL within the procedure, and its value is visible to the caller when the procedure returns. An INOUT parameter is initialized by the caller, can be modified by the procedure, and any change made by the procedure is visible to the caller when the procedure returns. For each OUT or INOUT parameter, pass a user-defined variable in the CALL statement that invokes the procedure so that you can obtain its value when the procedure returns. If you are calling the procedure from within another stored procedure or function, you can also pass a routine parameter or local routine variable as an IN or INOUT parameter. DETERMINISTIC/NOT DETERMINISTIC DETERMINISTIC and NOT DETERMINISTIC apply only to functions. Specifying DETERMINISTC or NON-DETERMINISTIC in procedures has no effect. The default value is NOT DETERMINISTIC. Functions are DETERMINISTIC when they always return the same value for the same input. For example, a truncate or substring function. Any function involving data, therefore, is always NOT DETERMINISTIC. CONTAINS SQL/NO SQL/READS SQL DATA/MODIFIES SQL DATA CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA are informative clauses that tell the server what the function does. MariaDB does not check in any way whether the specified clause is correct. If none of these clauses are specified, CONTAINS SQL is used by default. MODIFIES SQL DATA means that the function contains statements that may modify data stored in databases. This happens if the function contains statements like DELETE, UPDATE, INSERT, REPLACE or DDL. READS SQL DATA means that the function reads data stored in databases, but does not modify any data. This happens if SELECT statements are used, but there no write operations are executed. CONTAINS SQL means that the function contains at least one SQL statement, but it does not read or write any data stored in a database. Examples include SET or DO. NO SQL means nothing, because MariaDB does not currently support any language other than SQL. The routine_body consists of a valid SQL procedure statement. This can be a simple statement such as SELECT or INSERT, or it can be a compound statement written using BEGIN and END. Compound statements can contain declarations, loops, and other control structure statements. See Programmatic and Compound Statements for syntax details. MariaDB allows routines to contain DDL statements, such as CREATE and DROP. MariaDB also allows stored procedures (but not stored functions) to contain SQL transaction statements such as COMMIT. For additional information about statements that are not allowed in stored routines, see Stored Routine Limitations. Invoking stored procedure from within programs For information about invoking stored procedures from within programs written in a language that has a MariaDB/MySQL interface, see CALL. OR REPLACE If the optional OR REPLACE clause is used, it acts as a shortcut for: DROP PROCEDURE IF EXISTS name; CREATE PROCEDURE name ...; with the exception that any existing privileges for the procedure are not dropped. sql_mode MariaDB stores the sql_mode system variable setting that is in effect at the time a routine is created, and always executes the routine with this setting in force, regardless of the server SQL mode in effect when the routine is invoked. Character Sets and Collations Procedure parameters can be declared with any character set/collation. If the character set and collation are not specifically set, the database defaults at the time of creation will be used. If the database defaults change at a later stage, the stored procedure character set/collation will not be changed at the same time; the stored procedure needs to be dropped and recreated to ensure the same character set/collation as the database is used. Oracle Mode From MariaDB 10.3, a subset of Oracle's PL/SQL language has been supported in addition to the traditional SQL/PSM-based MariaDB syntax. See Oracle mode from MariaDB 10.3 for details on changes when running Oracle mode. Examples -------- The following example shows a simple stored procedure that uses an OUT parameter. It uses the DELIMITER command to set a new delimiter for the duration of the process — see Delimiters in the mysql client. DELIMITER // CREATE PROCEDURE simpleproc (OUT param1 INT) BEGIN SELECT COUNT(*) INTO param1 FROM t; END; // DELIMITER ; CALL simpleproc(@a); SELECT @a; +------+ | @a | +------+ | 1 | +------+ Character set and collation: DELIMITER // CREATE PROCEDURE simpleproc2 ( OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin' ) BEGIN SELECT CONCAT('a'),f1 INTO param1 FROM t; END; // DELIMITER ; CREATE OR REPLACE: DELIMITER // CREATE PROCEDURE simpleproc2 ( OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin' ) BEGIN SELECT CONCAT('a'),f1 INTO param1 FROM t; END; // ERROR 1304 (42000): PROCEDURE simpleproc2 already exists DELIMITER ; DELIMITER // CREATE OR REPLACE PROCEDURE simpleproc2 ( OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin' ) BEGIN SELECT CONCAT('a'),f1 INTO param1 FROM t; END; // ERROR 1304 (42000): PROCEDURE simpleproc2 already exists DELIMITER ; Query OK, 0 rows affected (0.03 sec) URL: https://mariadb.com/kb/en/create-procedure/^ ,('CREATE SERVERSyntax ------ CREATE [OR REPLACE] SERVER [IF NOT EXISTS] server_name FOREIGN DATA WRAPPER wrapper_name OPTIONS (option [, option] ...) option: { HOST character-literal | DATABASE character-literal | USER character-literal | PASSWORD character-literal | SOCKET character-literal | OWNER character-literal | PORT numeric-literal } Description ----------- This statement creates the definition of a server for use with the Spider, FEDERATED or FederatedX storage engine. The CREATE SERVER statement creates a new row within the servers table within the mysql database. This statement requires the SUPER privilege. The server_name should be a unique reference to the server. Server definitions are global within the scope of the server, it is not possible to qualify the server definition to a specific database. server_name has a maximum length of 64 characters (names longer than 64 characters are silently truncated), and is case insensitive. You may specify the name as a quoted string. The wrapper_name should be mysql, and may be quoted with single quotes. Other values for wrapper_name are not currently supported. For each option you must specify either a character literal or numeric literal. Character literals are UTF-8, support a maximum length of 64 characters and default to a blank (empty) string. String literals are silently truncated to 64 characters. Numeric literals must be a number between 0 and 9999, default value is 0. Note: The OWNER option is currently not applied, and has no effect on the ownership or operation of the server connection that is created. The CREATE SERVER statement creates an entry in the mysql.servers table that can later be used with the CREATE TABLE statement when creating a Spider, FederatedX or FEDERATED table. The options that you specify will be used to populate the columns in the mysql.servers table. The table columns are Server_name, Host, Db, Username, Password, Port and Socket. DROP SERVER removes a previously created server definition. CREATE SERVER is not written to the binary log, irrespective of the binary log format being used. For valid identifiers to use as server names, see Identifier Names. OR REPLACE If the optional OR REPLACE clause is used, it acts as a shortcut for: DROP SERVER IF EXISTS name; CREATE SERVER server_name ...; IF NOT EXISTS If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the server already exists. Cannot be used together with OR REPLACE. Examples -------- CREATE SERVER s FOREIGN DATA WRAPPER mysql OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test'); OR REPLACE and IF NOT EXISTS: CREATE SERVER s FOREIGN DATA WRAPPER mysql OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test'); ERROR 1476 (HY000): The foreign server, s, you are trying to create already exists CREATE OR REPLACE SERVER s FOREIGN DATA WRAPPER mysql OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test'); Query OK, 0 rows affected (0.00 sec) CREATE SERVER IF NOT EXISTS s FOREIGN DATA WRAPPER mysql OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test'); Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+----------------------------------------------------------------+ | Level | Code | Message | +-------+------+----------------------------------------------------------------+ | Note | 1476 | The foreign server, s, you are trying to create already exists | +-------+------+----------------------------------------------------------------+ URL: https://mariadb.com/kb/en/create-server/https://mariadb.com/kb/en/create-server/ %'DROP EVENTSyntax ------ DROP EVENT [IF EXISTS] event_name Description ----------- This statement drops the event named event_name. The event immediately ceases being active, and is deleted completely from the server. If the event does not exist, the error ERROR 1517 (HY000): Unknown event 'event_name' results. You can override this and cause the statement to generate a NOTE for non-existent events instead by using IF EXISTS. See SHOW WARNINGS. This statement requires the EVENT privilege. In MySQL 5.1.11 and earlier, an event could be dropped only by its definer, or by a user having the SUPER privilege. Examples -------- DROP EVENT myevent3; Using the IF EXISTS clause: DROP EVENT IF EXISTS myevent3; Query OK, 0 rows affected, 1 warning (0.01 sec) SHOW WARNINGS; +-------+------+-------------------------------+ | Level | Code | Message | +-------+------+-------------------------------+ | Note | 1305 | Event myevent3 does not exist | +-------+------+-------------------------------+ URL: https://mariadb.com/kb/en/drop-event/https://mariadb.com/kb/en/drop-event/ X('DROP FUNCTIONSyntax ------ DROP FUNCTION [IF EXISTS] f_name Description ----------- The DROP FUNCTION statement is used to drop a stored function or a user-defined function (UDF). That is, the specified routine is removed from the server, along with all privileges specific to the function. You must have the ALTER ROUTINE privilege for the routine in order to drop it. If the automatic_sp_privileges server system variable is set, both the ALTER ROUTINE and EXECUTE privileges are granted automatically to the routine creator - see Stored Routine Privileges. IF EXISTS The IF EXISTS clause is a MySQL/MariaDB extension. It prevents an error from occurring if the function does not exist. A NOTE is produced that can be viewed with SHOW WARNINGS. For dropping a user-defined functions (UDF), see DROP FUNCTION UDF. Examples -------- DROP FUNCTION hello; Query OK, 0 rows affected (0.042 sec) DROP FUNCTION hello; ERROR 1305 (42000): FUNCTION test.hello does not exist DROP FUNCTION IF EXISTS hello; Query OK, 0 rows affected, 1 warning (0.000 sec) SHOW WARNINGS; +-------+------+------------------------------------+ | Level | Code | Message | +-------+------+------------------------------------+ | Note | 1305 | FUNCTION test.hello does not exist | +-------+------+------------------------------------+ URL: https://mariadb.com/kb/en/drop-function/https://mariadb.com/kb/en/drop-function/{W o%m[Syntax ------ CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name (create_definition,...) [table_options ]... [partition_options] CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name [(create_definition,...)] [table_options ]... [partition_options] select_statement CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name { LIKE old_table_name | (LIKE old_table_name) } select_statement: [IGNORE | REPLACE] [AS] SELECT ... (Some legal select statement) Description ----------- Use the CREATE TABLE statement to create a table with the given name. In its most basic form, the CREATE TABLE statement provides a table name followed by a list of columns, indexes, and constraints. By default, the table is created in the default database. Specify a database with db_name.tbl_name. If you quote the table name, you must quote the database name and table name separately as `db_name`.`tbl_name`. This is particularly useful for CREATE TABLE ... SELECT, because it allows to create a table into a database, which contains data from other databases. See Identifier Qualifiers. If a table with the same name exists, error 1050 results. Use IF NOT EXISTS to suppress this error and issue a note instead. Use SHOW WARNINGS to see notes. The CREATE TABLE statement automatically commits the current transaction, except when using the TEMPORARY keyword. For valid identifiers to use as table names, see Identifier Names. Note: if the default_storage_engine is set to ColumnStore then it needs setting on all UMs. Otherwise when the tables using the default engine are replicated across UMs they will use the wrong engine. You should therefore not use this option as a session variable with ColumnStore. Microsecond precision can be between 0-6. If no precision is specified it is assumed to be 0, for backward compatibility reasons. Privileges Executing the CREATE TABLE statement requires the CREATE privilege for the table or the database. CREATE OR REPLACE TABLE ... The OR REPLACE clause was added in MariaDB 10.0.8. If the OR REPLACE clause is used and if the table already exists, then instead of returning an error, the server will drop the existing table and replace it with the newly defined table. This syntax was originally added to make replication more robust if it has to rollback and repeat statements such as CREATE ... SELECT on slaves. CREATE OR REPLACE TABLE table_name (a int); is basically the same as: DROP TABLE IF EXISTS table_name; CREATE TABLE table_name (a int); with the following exceptions: If table_name was locked with LOCK TABLES it will continue to be locked after the statement. Temporary tables are only dropped if the TEMPORARY keyword was used. (With DROP TABLE, temporary tables are preferred to be dropped before normal tables). Things to be Aware of With CREATE OR REPLACE The table is dropped first (if it existed), after that the CREATE is done. Because of this, if the CREATE fails, then the table will not exist anymore after the statement. If the table was used with LOCK TABLES it will be unlocked. One can't use OR REPLACE together with IF EXISTS. Slaves in replication will by default use CREATE OR REPLACE when replicating CREATE statements that don''t use IF EXISTS. This can be changed by setting the variable slave-ddl-exec-mode to STRICT. CREATE TABLE IF NOT EXISTS ... If the IF NOT EXISTS clause is used, then the index will only be created if an index with the same name does not already exist. If the index already exists, then a warning will be triggered by default. CREATE TEMPORARY TABLE ... Use the TEMPORARY keyword to create a temporary table that is only available to your current session. Temporary tables are dropped when the your session ends. Temporary table names are specific to your session. They will not conflict with other temporary tables from other session even if they share the same name. They will shadow names of non-temporary tables or views, if they are identical. A temporary table can have the same name as a non-temporary table which is located in the same database. In that case, their name will reference the temporary table when used in SQL statements. You must have the CREATE TEMPORARY TABLES privilege on the database to create temporary tables. If no storage engine is specified, the default_tmp_storage_engine setting will determine the engine. CREATE TABLE ... LIKE Use the LIKE clause instead of a full table definition to create a table with the same definition as another table, including columns, indexes, and table options. Foreign key definitions, as well as any DATA DIRECTORY or INDEX DIRECTORY table options specified on the original table, will not be created. CREATE TABLE ... SELECT You can create a table containing data from other tables using the CREATE ... SELECT statement. Columns will be created in the table for each field returned by the SELECT query. You can also define some columns normally and add other columns from a SELECT. You can also create columns in the normal way and assign them some values using the query, this is done to force a certain type or other field characteristics. The columns that are not named in the query will be placed before the others. For example: CREATE TABLE test (a INT NOT NULL, b CHAR(10)) ENGINE=MyISAM SELECT 5 AS b, c, d FROM another_table; Remember that the query just returns data. If you want to use the same indexes, or the same columns attributes ([NOT] NULL, DEFAULT, AUTO_INCREMENT) in the new table, you need to specify them manually. Types and sizes are not automatically preserved if no data returned by the SELECT requires the full size, and VARCHAR could be converted into CHAR. The CAST() function can be used to forcee the new table to use certain types. Aliases (AS) are taken into account, and they should always be used when you SELECT an expression (function, arithmetical operation, etc). If an error occurs during the query, the table will not be created at all. If the new table has a primary key or UNIQUE indexes, you can use the IGNORE or REPLACE keywords to handle duplicate key errors during the query. IGNORE means that the newer values must not be inserted an identical value exists in the index. REPLACE means that older values must be overwritten. If the columns in the new table are more than the rows returned by the query, the columns populated by the query will be placed after other columns. Note that if the strict SQL_MODE is on, and the columns that are not names in the query do not have a DEFAULT value, an error will raise and no rows will be copied. Concurrent inserts are not used during the execution of a CREATE ... SELECT. If the table already exists, an error similar to the following will be returned: ERROR 1050 (42S01): Table 't' already exists If the IF NOT EXISTS clause is used and the table exists, a note will be produced instead of an error. To insert rows from a query into an existing table, INSERT ... SELECT can be used. Column Definitions create_definition: { col_name column_definition | index_definition | period_definition | CHECK (expr) } column_definition: data_type [NOT NULL | NULL] [DEFAULT default_value | (expression)] [AUTO_INCREMENT] [ZEROFILL] [UNIQUE [KEY] | [PRIMARY] KEY] [INVISIBLE] [{WITH|WITHOUT} SYSTEM VERSIONING] [COMMENT 'string'] [COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}] [reference_definition] | data_type [GENERATED ALWAYS] AS { { ROW {START|END} } | { (expression) [VIRTUAL | PERSISTENT | STORED] } } [UNIQUE [KEY]] [COMMENT 'string'] constraint_definition: CONSTRAINT [constraint_name] CHECK (expression) Note: MariaDB accepts the REFERENCES clause in ALTER TABLE and CREATE TABLE column definitions, but that syntax does nothing. MariaDB simply parses it without returning any error or warning, for compatibility with other DBMS's. Before MariaDB 10.2.1 this was also true for CHECK constraints. Only the syntax for indexes described below creates foreign keys. Each definition either creates a column in the table or specifies and index or constraint on one or more columns. See Indexes below for details onU  creating indexes. Create a column by specifying a column name and a data type, optionally followed by column options. See Data Types for a full list of data types allowed in MariaDB. NULL and NOT NULL Use the NULL or NOT NULL options to specify that values in the column may or may not be NULL, respectively. By default, values may be NULL. See also NULL Values in MariaDB. DEFAULT Column Option The DEFAULT clause was enhanced in MariaDB 10.2.1. Some enhancements include BLOB and TEXT columns now support DEFAULT. The DEFAULT clause can now be used with an expression or function. Specify a default value using the DEFAULT clause. If you don't specify DEFAULT then the following rules apply: If the column is not defined with NOT NULL, AUTO_INCREMENT or TIMESTAMP, an explicit DEFAULT NULL will be added. Note that in MySQL and in MariaDB before 10.1.6, you may get an explicit DEFAULT for primary key parts, if not specified with NOT NULL. The default value will be used if you INSERT a row without specifying a value for that column, or if you specify DEFAULT for that column. Before MariaDB 10.2.1 you couldn't usually provide an expression or function to evaluate at insertion time. You had to provide a constant default value instead. The one exception is that you may use CURRENT_TIMESTAMP as the default value for a TIMESTAMP column to use the current timestamp at insertion time. CURRENT_TIMESTAMP may also be used as the default value for a DATETIME From MariaDB 10.2.1 you can use most functions in DEFAULT. Expressions should have parentheses around them. If you use a non deterministic function in DEFAULT then all inserts to the table will be replicated in row mode. You can even refer to earlier columns in the DEFAULT expression: CREATE TABLE t1 (a int DEFAULT (1+1), b int DEFAULT (a+1)); CREATE TABLE t2 (a bigint primary key DEFAULT UUID_SHORT()); The DEFAULT clause cannot contain any stored functions or subqueries, and a column used in the clause must already have been defined earlier in the statement. Since MariaDB 10.2.1, it is possible to assign BLOB or TEXT columns a DEFAULT value. In earlier versions, assigning a default to these columns was not possible. Starting from 10.3.3 you can also use DEFAULT (NEXT VALUE FOR sequence) AUTO_INCREMENT Column Option Use AUTO_INCREMENT to create a column whose value can can be set automatically from a simple counter. You can only use AUTO_INCREMENT on a column with an integer type. The column must be a key, and there can only be one AUTO_INCREMENT column in a table. If you insert a row without specifying a value for that column (or if you specify 0, NULL, or DEFAULT as the value), the actual value will be taken from the counter, with each insertion incrementing the counter by one. You can still insert a value explicitly. If you insert a value that is greater than the current counter value, the counter is set based on the new value. An AUTO_INCREMENT column is implicitly NOT NULL. Use LAST_INSERT_ID to get the AUTO_INCREMENT value most recently used by an INSERT statement. ZEROFILL Column Option If the ZEROFILL column option is specified for a column using a numeric data type, then the column will be set to UNSIGNED and the spaces used by default to pad the field are replaced with zeros. ZEROFILL is ignored in expressions or as part of a UNION. ZEROFILL is a non-standard MySQL and MariaDB enhancement. PRIMARY KEY Column Option Use PRIMARY KEY (or just KEY) to make a column a primary key. A primary key is a special type of a unique key. There can be at most one primary key per table, and it is implicitly NOT NULL. Specifying a column as a unique key creates a unique index on that column. See the Index Definitions section below for more information. UNIQUE KEY Column Option Use UNIQUE KEY (or just UNIQUE) to specify that all values in the column must be distinct from each other. Unless the column is NOT NULL, there may be multiple rows with NULL in the column. Specifying a column as a unique key creates a unique index on that column. See the Index Definitions section below for more information. COMMENT Column Option You can provide a comment for each column using the COMMENT clause. The maximum length is 1024 characters (it was 255 characters before MariaDB 5.5). Use the SHOW FULL COLUMNS statement to see column comments. Generated Columns A generated column is a column in a table that cannot explicitly be set to a specific value in a DML query. Instead, its value is automatically generated based on an expression. This expression might generate the value based on the values of other columns in the table, or it might generate the value by calling built-in functions or user-defined functions (UDFs). There are two types of generated columns: PERSISTENT or STORED: This type's value is actually stored in the table. VIRTUAL: This type's value is not stored at all. Instead, the value is generated dynamically when the table is queried. This type is the default. Generated columns are also sometimes called computed columns or virtual columns. For a complete description about generated columns and their limitations, see Generated (Virtual and Persistent/Stored) Columns. COLUMN_FORMAT COLUMN_FORMAT is only used by MySQL Cluster, and is silently ignored in MariaDB. COMPRESSED Certain columns may be compressed. See Storage-Engine Independent Column Compression. INVISIBLE Columns may be made invisible, and hidden in certain contexts. See Invisible Columns. WITH SYSTEM VERSIONING Column Option Columns may be explicitly marked as included from system versioning. See System-versioned tables for details. WITHOUT SYSTEM VERSIONING Column Option Columns may be explicitly marked as excluded from system versioning. See System-versioned tables for details. Index Definitions index_definition: {INDEX|KEY} [index_name] [index_type] (index_col_name,...) [index_option] ... | {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (index_col_name,...) [index_option] ... | [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...) [index_option] ... | [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY] [index_name] [index_type] (index_col_name,...) [index_option] ... | [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name,...) reference_definition index_col_name: col_name [(length)] [ASC | DESC] index_type: USING {BTREE | HASH | RTREE} index_option: KEY_BLOCK_SIZE [=] value | index_type | WITH PARSER parser_name | COMMENT 'string' | CLUSTERING={YES| NO} reference_definition: REFERENCES tbl_name (index_col_name,...) [MATCH FULL | MATCH PARTIAL | MATCH SIMPLE] [ON DELETE reference_option] [ON UPDATE reference_option] reference_option: RESTRICT | CASCADE | SET NULL | NO ACTION INDEX and KEY are synonyms. Index names are optional, if not specified an automatic name will be assigned. Index name are needed to drop indexes and appear in error messages when a constraint is violated. Index Categories Plain Indexes Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes. See Getting Started with Indexes: Plain Indexes for more information. PRIMARY KEY For PRIMARY KEY indexes, you can specify a name for the index, but it is silently ignored, and the name of the index is always PRIMARY. See Getting Started with Indexes: Primary Key for more information. UNIQUE The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index. For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages. See Getting Started with Indexes: Unique Index for more information. FOREIGN KEY For FOREIGN KEY indexes, a reference definition must be provided. For FOREIGN KEY indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages. First, you have to specify the name of the taarget (parent) table and a column or a column list which must be indexed and whose values must match to the foreign key's values. The MATCH clause is accepted to improve the compatibility with other DBMS's, but has no meaning in MariaDB. The ON DELETE and ON UPDATE clauses specify what must be done when a DELETE (or a REPLACE) statements attempts to delete a referenced row from the parent table, and when an UPDATE statement attempts to modify the referenced foreign key columns in a parent table row, respectively. The following options are allowed: RESTRICT: The delete/update operation is not performed. The statement terminates with a 1451 error (SQLSTATE '2300'). NO ACTION: Synonym for RESTRICT. CASCADE: The delete/update operation is performed in both tables. SET NULL: The update or delete goes ahead in the parent table, and the corresponding foreign key fields in the child table are set to NULL. (They must not be defined as NOT NULL for this to succeed). SET DEFAULT: This option is currently implemented only for the PBXT storage engine, which is disabled by default and no longer maintained. It sets the child table's foreign key fields to their DEFAULT values when the referenced parent table key entries are updated or deleted. If either clause is omitted, the default behavior for the omitted clause is RESTRICT. See Foreign Keys for more information. FULLTEXT Use the FULLTEXT keyword to create full-text indexes. See Full-Text Indexes for more information. SPATIAL Use the SPATIAL keyword to create geometric indexes. See SPATIAL INDEX for more information. Index Options KEY_BLOCK_SIZE Index Option The KEY_BLOCK_SIZE index option is similar to the KEY_BLOCK_SIZE table option. With the InnoDB storage engine, if you specify a non-zero value for the KEY_BLOCK_SIZE table option for the whole table, then the table will implicitly be created with the ROW_FORMAT table option set to COMPRESSED. However, this does not happen if you just set the KEY_BLOCK_SIZE index option for one or more indexes in the table. The InnoDB storage engine ignores the KEY_BLOCK_SIZE index option. However, the SHOW CREATE TABLE statement may still report it for the index. For information about the KEY_BLOCK_SIZE index option, see the KEY_BLOCK_SIZE table option below. Index Types Each storage engine supports some or all index types. See Storage Engine Index Types for details on permitted index types for each storage engine. Different index types are optimized for different kind of operations: BTREE is the default type, and normally is the best choice. It is supported by all storage engines. It can be used to compare a column's value with a value using the =, >, >=, 0) ,b int check (b> 0), constraint abc check (a>b)); If you use the second format and you don't give a name to the constraint, then the constraint will get a auto generated name. This is done so that you can later delete the constraint with ALTER TABLE DROP constraint_name. One can disable all constraint expression checks by setting the variable check_constraint_checks to OFF. This is useful for example when loading a table that violates some constraints that you want to later find and fix in SQL. See CONSTRAINT for more information. Table Options For each individual table you create (or alter), you can set some table options. The general syntax for setting options is: = , [ = ...] The equal sign is optional. Some options are supported by the server and can be used for all tables, no matter what storage engine they use; other options can be specified for all storage engines, but have a meaning only for some engines. Also, engines can extend CREATE TABLE with new options. If the IGNORE_BAD_TABLE_OPTIONS SQL_MODE is enabled, wrong table options generate a warning; otherwise, they generate an error. table_option: [STORAGE] ENGINE [=] engine_name | AUTO_INCREMENT [=] value | AVG_ROW_LENGTH [=] value | [DEFAULT] CHARACTER SET [=] charset_name | CHECKSUM [=] {0 | 1} | [DEFAULT] COLLATE [=] collation_name | COMMENT [=] 'string' | CONNECTION [=] 'connect_string' | DATA DIRECTORY [=] 'absolute path to directory' | DELAY_KEY_WRITE [=] {0 | 1} | ENCRYPTED [=] {YES | NO} | ENCRYPTION_KEY_ID [=] value | IETF_QUOTES [=] {YES | NO} | INDEX DIRECTORY [=] 'absolute path to directory' | INSERT_METHOD [=] { NO | FIRST | LAST } | KEY_BLOCK_SIZE [=] value | MAX_ROWS [=] value | MIN_ROWS [=] value | PACK_KEYS [=] {0 | 1 | DEFAULT} | PAGE_CHECKSUM [=] {0 | 1} | PAGE_COMPRESSED [=] {0 | 1} | PAGE_COMPRESSION_LEVEL [=] {0 .. 9} | PASSWORD [=] 'string' | ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT|PAGE} | SEQUENCE [=] {0|1} | STATS_AUTO_RECALC [=] {DEFAULT|0|1} | STATS_PERSISTENT [=] {DEFAULT|0|1} | STATS_SAMPLE_PAGES [=] {DEFAULT|value} | TABLESPACE tablespace_name | TRANSACTIONAL [=] {0 | 1} | UNION [=] (tbl_name[,tbl_name]...) | WITH SYSTEM VERSIONING [STORAGE] ENGINE [STORAGE] ENGINE specifies a storage engine for the table. If this option is not used, the default storage engine is used instead. That is, the storage_engine session option value if it is set, or the value specified for the --default-storage-engine mysqld startup options, or InnoDB. If the specified storage engine is not installed and active, the default value will be used, unless the NO_ENGINE_SUBSTITUTION SQL MODE is set (default since MariaDB 10.0). This is only true for CREATE TABLE, not for ALTER TABLE. For a list of storage engines that are present in your server, issue a SHOW ENGINES. AUTO_INCREMENT AUTO_INCREMENT specifies the initial value for the AUTO_INCREMENT primary key. This works for MyISAM, Aria, InnoDB/XtraDB, MEMORY, and ARCHIVE tables. You can change this option with ALTER TABLE, but in that case the new value must be higher than the highest value which is present in the AUTO_INCREMENT column. If the storage engine does not support this option, you can insert (and then delete) a row having the wanted value - 1 in the AUTO_INCREMENT column. AVG_ROW_LENGTH AVG_ROW_LENGTH is the average rows size. It only applies to tables using MyISAM and Aria storage engines that have the ROW_FORMAT table option set to FIXED format. MyISAM uses MAX_ROWS and AVG_ROW_LENGTH to decide the maximum size of a table (default: 256TB, or the maximum file size allowed by the system). [DEFAULT] CHARACTER SET/CHARSET [DEFAULT] CHARACTER SET (or [DEFAULT] CHARSET) is used to set a default character set for the table. This is the character set used for all columns where an explicit character set is not specified. If this option is omitted or DEFAULT is specified, database's default character set will be used. See Setting Character Sets and Collations for details on setting the character sets. CHECKSUM/TABLE_CHECKSUM CHECKSUM (or TABLE_CHECKSUM) can be set to 1 to maintain a live checksum for all table's rows. This makes write operations slower, but CHECKSUM TABLE will be very fast. This option is only supported for MyISAM and Aria tables. [DEFAULT] COLLATE [DEFAULT] COLLATE is used to set a default collation for the table. This is the collation used for all columns where an explicit character set is not specified. If this option is omitted or DEFAULT is specified, database's default option will be used. See Setting Character Sets and Collations for details on setting the collations COMMENT COMMENT is a comment for the table. Maximum length is 2048 characters (before mariaDB 5.5 it was 60 characters). Also used to define table parameters when creating a Spider table. CONNECTION CONNECTION is used to specify a server name or a connection string for a Spider, CONNECT, Federated or FederatedX table. DATA DIRECTORY/INDEX DIRECTORY DATA DIRECTORY and INDEX DIRECTORY were only supported for MyISAM and Aria, before MariaDB 5.5. Since 5.5, DATA DIRECTORY has also been supported by InnoDB if the innodb_file_per_table server system variable is enabled, but only in CREATE TABLE, not in ALTER TABLE. So, carefully choose a path for InnoDB tables at creation time, because it cannot be changed without dropping and re-creating the table. Thnese options specify the paths for data files and index files, respectively. If these options are omitted, the database's directory will be used to store data files and index files. Note that these table options do not work for partitioned tables (use the partition options instead), or if the server has been invoked with the --skip-symbolic-links startup option. To avoid the overwriting of old files with the same name that could be present in the directories, you can use the --keep_files_on_create option (an error will be issued if files already exist). These options are ignored if the NO_DIR_IN_CREATE SQL_MODE is enabled (useful for replication slaves). Also note that symbolic links cannot be used for InnoDB tables. DATA DIRECTORY works by creating symlinks from where the table would normally have been (inside the datadir) to where the option specifies. For security reasons, to avoid bypassing the privilege system, the server does not permit symlinks inside the datadir. Therefore, DATA DIRECTORY cannot be used to specify a location inside the datadir. An attempt to do so will result in an error 1210 (HY000) Incorrect arguments to DATA DIRECTORY. DELAY_KEY_WRITE DELAY_KEY_WRITE is supported by MyISAM and Aria, and can be set to 1 to speed up write operations. In that case, when data are modified, the indexes are not updated until the table is closed. Writing the changes to the index file altogether can be much faster. However, note that this option is applied only if the delay_key_write server variable is set to 'ON'. If it is 'OFF' the delayed index writes are always disabled, and if it is 'ALL' the delayed index writes are always used, disregarding the value of DELAY_KEY_WRITE. ENCRYPTED The ENCRYPTED table option was added in MariaDB 10.1.4 The ENCRYPTED table option can be used to manually set the encryption status of an InnoDB table. See InnoDB / XtraDB Encryption for more information. Aria does not currently support the ENCRYPTED table option. See MDEV-18049 about that. See Data-at-Rest Encryption for more information. ENCRYPTION_KEY_ID The ENCRYPTION_KEY_ID table option was added in MariaDB 10.1.4 The ENCRYPTION_KEY_ID table option can be used to manually set the encryption key of an InnoDB table. See InnoDB / XtraDB Encryption for more information. Aria does not currently support the ENCRYPTION_KEY_ID table option. See MDEV-18049 about that. See Data-at-Rest Encryption for more information. IETF_QUOTES The IETF_QUOTES option was added in MariaDB 10.1.8 For the CSV storage engine, the IETF_QUOTES option, when set to YES, enables IETF-compatible parsing of embedded quote and comma characters. Enabling this option for a table improves compatibility with other tools that use CSV, but is not compatible with MySQL CSV tables, or MariaDB CSV tables created without this option. Disabled by default. INSERT_METHOD INSERT_METHOD is only used with MERGE tables. This option determines in which underlying table the new rows should be inserted. If you set it to 'NO' (which is the default) no new rows can be added to the table (but you will still be able to perform INSERTs directly against the underlying tables). FIRST means that the rows are inserted into the first table, and LAST means that thet are inserted into the last table. KEY_BLOCK_SIZE KEY_BLOCK_SIZE is used to determine the size of key blocks, in bytes or kilobytes. However, this value is just a hint, and the storage engine could modify or ignore it. If KEY_BLOCK_SIZE is set to 0, the storage engine's default value will be used. With the InnoDB storage engine, if you specify a non-zero value for the KEY_BLOCK_SIZE table option for the whole table, then the table will implicitly be created with the ROW_FORMAT table option set to COMPRESSED. MIN_ROWS/MAX_ROWS MIN_ROWS and MAX_ROWS let the storage engine know how many rows you are planning to store as a minimum and as a maximum. These values will not be used as real limits, but they help the storage engine to optimize the table. MIN_ROWS is only used by MEMORY storage engine to decide the minimum memory that is always allocated. MAX_ROWS is used to decide the minimum size for indexes. PACK_KEYS PACK_KEYS can be used to determine whether the indexes will be compressed. Set it to 1 to compress all keys. With a value of 0, compression will not be used. With the DEFAULT value, only long strings will be compressed. Uncompressed keys are faster. PAGE_CHECKSUM PAGE_CHECKSUM is only applicable to Aria tables, and determines whether indexes and data should use page checksums for extra safety. PAGE_COMPRESSED PAGE_COMPRESSED is used to enable InnoDB page compression for InnoDB tables. PAGE_COMPRESSION_LEVEL PAGE_COMPRESSION_LEVEL is used to set the compression level for InnoDB page compression for InnoDB tables. The table must also have the PAGE_COMPRESSED table option set to 1. Valid values for PAGE_COMPRESSION_LEVEL are 1 (the best speed) through 9 (the best compression), . PASSWORD PASSWORD is unused. RAID_TYPE RAID_TYPE is an obsolete option, as the raid support has been disabled since MySQL 5.0. ROW_FORMAT The ROW_FORMAT table option specifies the row format for the data file. Possible values are engine-dependent. Supported MyISAM Row Formats For MyISAM, the supported row formats are: FIXED DYNAMIC COMPRESSED The COMPRESSED row format can only be set by the myisampack command line tool. See MyISAM Storage Formats for more information. Supported Aria Row Formats For Aria, the supported row formats are: PAGE FIXED DYNAMIC. See Aria Storage Formats for more information. Supported InnoDB Row Formats For InnoDB/XtraDB, the supported row formats are: COMPACT REDUNDANT COMPRESSED DYNAMIC. If the ROW_FORMAT table option is set to FIXED for an InnoDB table, then the server will either return an error or a warning depending on the value of the innodb_strict_mode system variable. If the innodb_strict_mode system variable is set to OFF, then a warning is issued, and MariaDB will create the table using the default row format for the specific MariaDB server version. If the innodb_strict_mode system variable is set to ON, then an error will be raised. See XtraDB/InnoDB Storage Formats for more information. Other Storage Engines and ROW_FORMAT Other storage engines do not support the ROW_FORMAT table option. SEQUENCE If the table is a sequence, then it will have the SEQUENCE set to 1. STATS_AUTO_RECALC STATS_AUTO_RECALC is available only in MariaDB 10.0+. It indicates whether to automatically recalculate persistent statistics (see STATS_PERSISTENT, below) for an InnoDB table. If set to 1, statistics will be recalculated when more than 10% of the data has changed. When set to 0, stats will be recalculated only when an ANALYZE TABLE is run. If set to DEFAULT, or left out, the value set by the innodb_stats_auto_recalc system variable applies. See InnoDB Persistent Statistics. STATS_PERSISTENT STATS_PERSISTENT is available only in MariaDB 10.0+. It indicates whether the InnoDB statistics created by ANALYZE TABLE will remain on disk or not. It can be set to 1 (on disk), 0 (not on disk, the pre-MariaDB 10 behavior), or DEFAULT (the same as leaving out the option), in which case the value set by the innodb_stats_persistent system variable will apply. Persistent statistics stored on disk allow the statistics to survive server restarts, and provide better query plan stability. See InnoDB Persistent Statistics. STATS_SAMPLE_PAGES STATS_SAMPLE_PAGES is available only in MariaDB 10.0+. It indicates how many pages are used to sample index statistics. If 0 or DEFAULT, the default value, the innodb_stats_sample_pages value is used. See InnoDB Persistent Statistics. TRANSACTIONAL TRANSACTIONAL is only applicable for Aria tables. In future Aria tables created with this option will be fully transactional, but currently this provides a form of crash protection. See Aria Storage Engine for more details. UNION UNION must be specified when you create a MERGE table. This option contains a comma-separated list of MyISAM tables which are accesse&d by the new table. The list is enclosed between parenthesis. Example: UNION = (t1,t2) WITH SYSTEM VERSIONING WITH SYSTEM VERSIONING is used for creating System-versioned tables. Partitions partition_options: PARTITION BY { [LINEAR] HASH(expr) | [LINEAR] KEY(column_list) | RANGE(expr) | LIST(expr) | SYSTEM_TIME [INTERVAL time_quantity time_unit] [LIMIT num] } [PARTITIONS num] [SUBPARTITION BY { [LINEAR] HASH(expr) | [LINEAR] KEY(column_list) } [SUBPARTITIONS num] ] [(partition_definition [, partition_definition] ...)] partition_definition: PARTITION partition_name [VALUES {LESS THAN {(expr) | MAXVALUE} | IN (value_list)}] [[STORAGE] ENGINE [=] engine_name] [COMMENT [=] 'comment_text' ] [DATA DIRECTORY [=] 'data_dir'] [INDEX DIRECTORY [=] 'index_dir'] [MAX_ROWS [=] max_number_of_rows] [MIN_ROWS [=] min_number_of_rows] [TABLESPACE [=] tablespace_name] [NODEGROUP [=] node_group_id] [(subpartition_definition [, subpartition_definition] ...)] subpartition_definition: SUBPARTITION logical_name [[STORAGE] ENGINE [=] engine_name] [COMMENT [=] 'comment_text' ] [DATA DIRECTORY [=] 'data_dir'] [INDEX DIRECTORY [=] 'index_dir'] [MAX_ROWS [=] max_number_of_rows] [MIN_ROWS [=] min_number_of_rows] [TABLESPACE [=] tablespace_name] [NODEGROUP [=] node_group_id] If the PARTITION BY clause is used, the table will be partitioned. A partition method must be explicitly indicated for partitions and subpartitions. Partition methods are: [LINEAR] HASH creates a hash key which will be used to read and write rows. The partition function can be any valid SQL expression which returns an INTEGER number. Thus, it is possible to use the HASH method on an integer column, or on functions which accept integer columns as an argument. However, VALUES LESS THAN and VALUES IN clauses can not be used with HASH. An example: CREATE TABLE t1 (a INT, b CHAR(5), c DATETIME) PARTITION BY HASH ( YEAR(c) ); [LINEAR] HASH can be used for subpartitions, too. [LINEAR] KEY is similar to HASH, but the index has an even distribution of data. Also, the expression can only be a column or a list of columns. VALUES LESS THAN and VALUES IN clauses can not be used with KEY. RANGE partitions the rows using on a range of values, using the VALUES LESS THAN operator. VALUES IN is not allowed with RANGE. The partition function can be any valid SQL expression which returns a single value. LIST assignes partitions based on a table's column with a restricted set of possible values. It is similar to RANGE, but VALUES IN must be used for at least 1 columns, and VALUES LESS THAN is disallowed. SYSTEM_TIME partitioning is used for System-versioned tables to store historical data separately from current data. Only HASH and KEY can be used for subpartitions, and they can be [LINEAR]. It is possible to define up to 1024 partitions and subpartitions. The number of defined partitions can be optionally specified as PARTITION count. This can be done to avoid specifying all partitions individually. But you can also declare each individual partition and, additionally, specify a PARTITIONS count clause; in the case, the number of PARTITIONs must equal count. Also see Partitioning Types Overview. Sequences CREATE TABLE can also be used to create a SEQUENCE. See CREATE SEQUENCE and Sequence Overview. Examples -------- create table if not exists test ( a bigint auto_increment primary key, name varchar(128) charset utf8, key name (name(32)) ) engine=InnoDB default charset latin1; This example shows a couple of things: Usage of IF NOT EXISTS; If the table already existed, it will not be created. There will not be any error for the client, just a warning. How to create a PRIMARY KEY that is automatically generated. How to specify a table-specific character set and another for a column. How to create an index (name) that is only partly indexed (to save space). The following clauses will work from MariaDB 10.2.1 only. CREATE TABLE t1( a int DEFAULT (1+1), b int DEFAULT (a+1), expires DATETIME DEFAULT(NOW() + INTERVAL 1 YEAR), x BLOB DEFAULT USER() ); URL: https://mariadb.com/kb/en/create-table/ ARl )'CREATE TRIGGERSyntax ------ CREATE [OR REPLACE] [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }] TRIGGER [IF NOT EXISTS] trigger_name trigger_time trigger_event ON tbl_name FOR EACH ROW [{ FOLLOWS | PRECEDES } other_trigger_name ] trigger_stmt Description ----------- This statement creates a new trigger. A trigger is a named database object that is associated with a table, and that activates when a particular event occurs for the table. The trigger becomes associated with the table named tbl_name, which must refer to a permanent table. You cannot associate a trigger with a TEMPORARY table or a view. CREATE TRIGGER requires the TRIGGER privilege for the table associated with the trigger. (Before MySQL 5.1.6, this statement requires the SUPER privilege.) You can have multiple triggers for the same trigger_time and trigger_event. For valid identifiers to use as trigger names, see Identifier Names. OR REPLACE If used and the trigger already exists, instead of an error being returned, the existing trigger will be dropped and replaced by the newly defined trigger. DEFINER The DEFINER clause determines the security context to be used when checking access privileges at trigger activation time. IF NOT EXISTS If the IF NOT EXISTS clause is used, the trigger will only be created if a trigger of the same name does not exist. If the trigger already exists, by default a warning will be returned. trigger_time trigger_time is the trigger action time. It can be BEFORE or AFTER to indicate that the trigger activates before or after each row to be modified. trigger_event trigger_event indicates the kind of statement that activates the trigger. The trigger_event can be one of the following: INSERT: The trigger is activated whenever a new row is inserted into the table; for example, through INSERT, LOAD DATA, and REPLACE statements. UPDATE: The trigger is activated whenever a row is modified; for example, through UPDATE statements. DELETE: The trigger is activated whenever a row is deleted from the table; for example, through DELETE and REPLACE statements. However, DROP TABLE and TRUNCATE statements on the table do not activate this trigger, because they do not use DELETE. Dropping a partition does not activate DELETE triggers, either. FOLLOWS/PRECEDES other_trigger_name The FOLLOWS other_trigger_name and PRECEDES other_trigger_name options were added in MariaDB 10.2.3 as part of supporting multiple triggers per action time. This is the same syntax used by MySQL 5.7, although MySQL 5.7 does not have multi-trigger support. FOLLOWS adds the new trigger after another trigger while PRECEDES adds the new trigger before another trigger. If neither option is used, the new trigger is added last for the given action and time. FOLLOWS and PRECEDES are not stored in the trigger definition. However the trigger order is guaranteed to not change over time. mysqldump and other backup methods will not change trigger order. You can verify the trigger order from the ACTION_ORDER column in INFORMATION_SCHEMA.TRIGGERS table. SELECT trigger_name, action_order FROM information_schema.triggers WHERE event_object_table='t1'; Examples -------- CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal AFTER INSERT ON animals FOR EACH ROW UPDATE animal_count SET animal_count.animals = animal_count.animals+1; OR REPLACE and IF NOT EXISTS CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal AFTER INSERT ON animals FOR EACH ROW UPDATE animal_count SET animal_count.animals = animal_count.animals+1; ERROR 1359 (HY000): Trigger already exists CREATE OR REPLACE DEFINER=`root`@`localhost` TRIGGER increment_animal AFTER INSERT ON animals FOR EACH ROW UPDATE animal_count SET animal_count.animals = animal_count.animals+1; Query OK, 0 rows affected (0.12 sec) CREATE DEFINER=`root`@`localhost` TRIGGER IF NOT EXISTS increment_animal AFTER INSERT ON animals FOR EACH ROW UPDATE animal_count SET animal_count.animals = animal_count.animals+1; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+------------------------+ | Level | Code | Message | +-------+------+------------------------+ | Note | 1359 | Trigger already exists | +-------+------+------------------------+ 1 row in set (0.00 sec) URL: https://mariadb.com/kb/en/create-trigger/https://mariadb.com/kb/en/create-trigger/ %'DROP INDEXSyntax ------ DROP INDEX [IF EXISTS] index_name ON tbl_name [WAIT n |NOWAIT] [algorithm_option | lock_option] ... algorithm_option: ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT} lock_option: LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE} Description ----------- DROP INDEX drops the index named index_name from the table tbl_name. This statement is mapped to an ALTER TABLE statement to drop the index. If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables. See ALTER TABLE. Another shortcut, CREATE INDEX, allows the creation of an index. To remove the primary key, `PRIMARY` must be specified as index_name. Note that the quotes are necessary, because PRIMARY is a keyword. Privileges Executing the DROP INDEX statement requires the INDEX privilege for the table or the database. Online DDL In MariaDB 10.0 and later, online DDL is supported with the ALGORITHM and LOCK clauses. See InnoDB Online DDL Overview for more information on online DDL with InnoDB. DROP INDEX IF EXISTS ... The IF EXISTS clause was added in MariaDB 10.1.4. If the IF EXISTS clause is used, then MariaDB will return a warning instead of an error if the index does not exist. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. ALGORITHM See ALTER TABLE: ALGORITHM for more information. LOCK See ALTER TABLE: LOCK for more information. Progress Reporting MariaDB provides progress reporting for DROP INDEX statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this:: URL: https://mariadb.com/kb/en/drop-index/https://mariadb.com/kb/en/drop-index/Z. Nx>Syntax ------ CREATE [OR REPLACE] [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}] [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }] [SQL SECURITY { DEFINER | INVOKER }] VIEW [IF NOT EXISTS] view_name [(column_list)] AS select_statement [WITH [CASCADED | LOCAL] CHECK OPTION] Description ----------- The CREATE VIEW statement creates a new view, or replaces an existing one if the OR REPLACE clause is given. If the view does not exist, CREATE OR REPLACE VIEW is the same as CREATE VIEW. If the view does exist, CREATE OR REPLACE VIEW is the same as ALTER VIEW. The select_statement is a SELECT statement that provides the definition of the view. (When you select from the view, you select in effect using the SELECT statement.) select_statement can select from base tables or other views. The view definition is "frozen" at creation time, so changes to the underlying tables afterwards do not affect the view definition. For example, if a view is defined as SELECT * on a table, new columns added to the table later do not become part of the view. A SHOW CREATE VIEW shows that such queries are rewritten and column names are included in the view definition. The view definition must be a query that does not return errors at view creation times. However, the base tables used by the views might be altered later and the query may not be valid anymore. In this case, querying the view will result in an error. CHECK TABLE helps in finding this kind of problems. The ALGORITHM clause affects how MariaDB processes the view. The DEFINER and SQL SECURITY clauses specify the security context to be used when checking access privileges at view invocation time. The WITH CHECK OPTION clause can be given to constrain inserts or updates to rows in tables referenced by the view. These clauses are described later in this section. The CREATE VIEW statement requires the CREATE VIEW privilege for the view, and some privilege for each column selected by the SELECT statement. For columns used elsewhere in the SELECT statement you must have the SELECT privilege. If the OR REPLACE clause is present, you must also have the DROP privilege for the view. A view belongs to a database. By default, a new view is created in the default database. To create the view explicitly in a given database, specify the name as db_name.view_name when you create it. CREATE VIEW test.v AS SELECT * FROM t; Base tables and views share the same namespace within a database, so a database cannot contain a base table and a view that have the same name. Views must have unique column names with no duplicates, just like base tables. By default, the names of the columns retrieved by the SELECT statement are used for the view column names. To define explicit names for the view columns, the optional column_list clause can be given as a list of comma-separated identifiers. The number of names in column_list must be the same as the number of columns retrieved by the SELECT statement. MySQL until 5.1.28 Prior to MySQL 5.1.29, When you modify an existing view, the current view definition is backed up and saved. It is stored in that table's database directory, in a subdirectory named arc. The backup file for a view v is named v.frm-00001. If you alter the view again, the next backup is named v.frm-00002. The three latest view backup definitions are stored. Backed up view definitions are not preserved by mysqldump, or any other such programs, but you can retain them using a file copy operation. However, they are not needed for anything but to provide you with a backup of your previous view definition. It is safe to remove these backup definitions, but only while mysqld is not running. If you delete the arc subdirectory or its files while mysqld is running, you will receive an error the next time you try to alter the view: MariaDB [test]> ALTER VIEW v AS SELECT * FROM t; ERROR 6 (HY000): Error on delete of '.\test\arc/v.frm-0004' (Errcode: 2) Columns retrieved by the SELECT statement can be simple references to table columns. They can also be expressions that use functions, constant values, operators, and so forth. Unqualified table or view names in the SELECT statement are interpreted with respect to the default database. A view can refer to tables or views in other databases by qualifying the table or view name with the proper database name. A view can be created from many kinds of SELECT statements. It can refer to base tables or other views. It can use joins, UNION, and subqueries. The SELECT need not even refer to any tables. The following example defines a view that selects two columns from another table, as well as an expression calculated from those columns: CREATE TABLE t (qty INT, price INT); INSERT INTO t VALUES(3, 50); CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t; SELECT * FROM v; +------+-------+-------+ | qty | price | value | +------+-------+-------+ | 3 | 50 | 150 | +------+-------+-------+ A view definition is subject to the following restrictions: The SELECT statement cannot contain a subquery in the FROM clause. The SELECT statement cannot refer to system or user variables. Within a stored program, the definition cannot refer to program parameters or local variables. The SELECT statement cannot refer to prepared statement parameters. Any table or view referred to in the definition must exist. However, after a view has been created, it is possible to drop a table or view that the definition refers to. In this case, use of the view results in an error. To check a view definition for problems of this kind, use the CHECK TABLE statement. The definition cannot refer to a TEMPORARY table, and you cannot create a TEMPORARY view. Any tables named in the view definition must exist at definition time. You cannot associate a trigger with a view. For valid identifiers to use as view names, see Identifier Names. ORDER BY is allowed in a view definition, but it is ignored if you select from a view using a statement that has its own ORDER BY. For other options or clauses in the definition, they are added to the options or clauses of the statement that references the view, but the effect is undefined. For example, if a view definition includes a LIMIT clause, and you select from the view using a statement that has its own LIMIT clause, it is undefined which limit applies. This same principle applies to options such as ALL, DISTINCT, or SQL_SMALL_RESULT that follow the SELECT keyword, and to clauses such as INTO, FOR UPDATE, and LOCK IN SHARE MODE. The PROCEDURE clause cannot be used in a view definition, and it cannot be used if a view is referenced in the FROM clause. If you create a view and then change the query processing environment by changing system variables, that may affect the results that you get from the view: CREATE VIEW v (mycol) AS SELECT 'abc'; SET sql_mode = ''; SELECT "mycol" FROM v; +-------+ | mycol | +-------+ | mycol | +-------+ SET sql_mode = 'ANSI_QUOTES'; SELECT "mycol" FROM v; +-------+ | mycol | +-------+ | abc | +-------+ The DEFINER and SQL SECURITY clauses determine which MariaDB account to use when checking access privileges for the view when a statement is executed that references the view. They were added in MySQL 5.1.2. The legal SQL SECURITY characteristic values are DEFINER and INVOKER. These indicate that the required privileges must be held by the user who defined or invoked the view, respectively. The default SQL SECURITY value is DEFINER. If a user value is given for the DEFINER clause, it should be a MariaDB account in 'user_name'@'host_name' format (the same format used in the GRANT statement). The user_name and host_name values both are required. The definer can also be given as CURRENT_USER or CURRENT_USER(). The default DEFINER value is the user who executes the CREATE VIEW statement. This is the same as specifying DEFINER = CURRENT_USER explicitly. If you specify the DEFINER clause, these rules determine the legal DEFINER user values: If you do not have the SUPER privilege, the only legal user value is your own account, either specified literally or by using CURxRENT_USER. You cannot set the definer to some other account. If you have the SUPER privilege, you can specify any syntactically legal account name. If the account does not actually exist, a warning is generated. If the SQL SECURITY value is DEFINER but the definer account does not exist when the view is referenced, an error occurs. Within a view definition, CURRENT_USER returns the view's DEFINER value by default. Before MySQL 5.1.12, and for views defined with the SQL SECURITY INVOKER characteristic, CURRENT_USER returns the account for the view's invoker. For information about user auditing within views, see http://dev.mysql.com/doc/refman/5.1/en/account-activity-auditing.html. Within a stored routine that is defined with the SQL SECURITY DEFINER characteristic, CURRENT_USER returns the routine's DEFINER value. This also affects a view defined within such a program, if the view definition contains a DEFINER value of CURRENT_USER. View privileges are checked like this: At view definition time, the view creator must have the privileges needed to use the top-level objects accessed by the view. For example, if the view definition refers to table columns, the creator must have privileges for the columns, as described previously. If the definition refers to a stored function, only the privileges needed to invoke the function can be checked. The privileges required when the function runs can be checked only as it executes: For different invocations of the function, different execution paths within the function might be taken. When a view is referenced, privileges for objects accessed by the view are checked against the privileges held by the view creator or invoker, depending on whether the SQL SECURITY characteristic is DEFINER or INVOKER, respectively. If reference to a view causes execution of a stored function, privilege checking for statements executed within the function depend on whether the function is defined with a SQL SECURITY characteristic of DEFINER or INVOKER. If the security characteristic is DEFINER, the function runs with the privileges of its creator. If the characteristic is INVOKER, the function runs with the privileges determined by the view's SQL SECURITY characteristic. MySQL until 5.1.1 Prior to MySQL 5.1.2 (before the DEFINER and SQL SECURITY clauses were implemented), privileges required for objects used in a view are checked at view creation time. Example: A view might depend on a stored function, and that function might invoke other stored routines. For example, the following view invokes a stored function f(): CREATE VIEW v AS SELECT * FROM t WHERE t.id = f(t.name); Suppose that f() contains a statement such as this: IF name IS NULL then CALL p1(); ELSE CALL p2(); END IF; The privileges required for executing statements within f() need to be checked when f() executes. This might mean that privileges are needed for p1() or p2(), depending on the execution path within f(). Those privileges must be checked at runtime, and the user who must possess the privileges is determined by the SQL SECURITY values of the view v and the function f(). The DEFINER and SQL SECURITY clauses for views are extensions to standard SQL. In standard SQL, views are handled using the rules for SQL SECURITY INVOKER. If you invoke a view that was created before MySQL 5.1.2, it is treated as though it was created with a SQL SECURITY DEFINER clause and with a DEFINER value that is the same as your account. However, because the actual definer is unknown, MySQL issues a warning. To make the warning go away, it is sufficient to re-create the view so that the view definition includes a DEFINER clause. The optional ALGORITHM clause is an extension to standard SQL. It affects how MariaDB processes the view. ALGORITHM takes three values: MERGE, TEMPTABLE, or UNDEFINED. The default algorithm is UNDEFINED if no ALGORITHM clause is present. See View Algorithms for more information. Some views are updatable. That is, you can use them in statements such as UPDATE, DELETE, or INSERT to update the contents of the underlying table. For a view to be updatable, there must be a one-to-one relationship between the rows in the view and the rows in the underlying table. There are also certain other constructs that make a view non-updatable. See Inserting and Updating with Views. WITH CHECK OPTION The WITH CHECK OPTION clause can be given for an updatable view to prevent inserts or updates to rows except those for which the WHERE clause in the select_statement is true. In a WITH CHECK OPTION clause for an updatable view, the LOCAL and CASCADED keywords determine the scope of check testing when the view is defined in terms of another view. The LOCAL keyword restricts the CHECK OPTION only to the view being defined. CASCADED causes the checks for underlying views to be evaluated as well. When neither keyword is given, the default is CASCADED. For more information about updatable views and the WITH CHECK OPTION clause, see Inserting and Updating with Views. IF NOT EXISTS The IF NOT EXISTS clause was added in MariaDB 10.1.3 When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified view already exists. Cannot be used together with the OR REPLACE clause. Examples -------- CREATE TABLE t (a INT, b INT) ENGINE = InnoDB; INSERT INTO t VALUES (1,1), (2,2), (3,3); CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t; SELECT * FROM v; +------+------+ | a | a2 | +------+------+ | 1 | 2 | | 2 | 4 | | 3 | 6 | +------+------+ OR REPLACE and IF NOT EXISTS: CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t; ERROR 1050 (42S01): Table 'v' already exists CREATE OR REPLACE VIEW v AS SELECT a, a*2 AS a2 FROM t; Query OK, 0 rows affected (0.04 sec) CREATE VIEW IF NOT EXISTS v AS SELECT a, a*2 AS a2 FROM t; Query OK, 0 rows affected, 1 warning (0.01 sec) SHOW WARNINGS; +-------+------+--------------------------+ | Level | Code | Message | +-------+------+--------------------------+ | Note | 1050 | Table 'v' already exists | +-------+------+--------------------------+ URL: https://mariadb.com/kb/en/create-view/%l= G)'DROP PROCEDURESyntax ------ DROP PROCEDURE [IF EXISTS] sp_name Description ----------- This statement is used to drop a stored procedure. That is, the specified routine is removed from the server along with all privileges specific to the procedure. You must have the ALTER ROUTINE privilege for the routine. If the automatic_sp_privileges server system variable is set, that privilege and EXECUTE are granted automatically to the routine creator - see Stored Routine Privileges. The IF EXISTS clause is a MySQL/MariaDB extension. It prevents an error from occurring if the procedure or function does not exist. A NOTE is produced that can be viewed with SHOW WARNINGS. While this statement takes effect immediately, threads which are executing a procedure can continue execution. Examples -------- DROP PROCEDURE simpleproc; IF EXISTS: DROP PROCEDURE simpleproc; ERROR 1305 (42000): PROCEDURE test.simpleproc does not exist DROP PROCEDURE IF EXISTS simpleproc; Query OK, 0 rows affected, 1 warning (0.00 sec) SHOW WARNINGS; +-------+------+------------------------------------------+ | Level | Code | Message | +-------+------+------------------------------------------+ | Note | 1305 | PROCEDURE test.simpleproc does not exist | +-------+------+------------------------------------------+ URL: https://mariadb.com/kb/en/drop-procedure/https://mariadb.com/kb/en/drop-procedure/ ('DROP SEQUENCEDROP SEQUENCE was introduced in MariaDB 10.3. Syntax ------ DROP [TEMPORARY] SEQUENCE [IF EXISTS] [/*COMMENT TO SAVE*/] sequence_name [, sequence_name] ... Description ----------- DROP SEQUENCE removes one or more sequences created with CREATE SEQUENCE. You must have the DROP privilege for each sequence. MariaDB returns an error indicating by name which non-existing tables it was unable to drop, but it also drops all of the tables in the list that do exist. Important: When a table is dropped, user privileges on the table are not automatically dropped. See GRANT. If another connection is using the sequence, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables. For each referenced sequence, DROP SEQUENCE drops a temporary sequence with that name, if it exists. If it does not exist, and the TEMPORARY keyword is not used, it drops a non-temporary sequence with the same name, if it exists. The TEMPORARY keyword ensures that a non-temporary sequence will not accidentally be dropped. Use IF EXISTS to prevent an error from occurring for sequences that do not exist. A NOTE is generated for each non-existent sequence when using IF EXISTS. See SHOW WARNINGS. DROP SEQUENCE requires the DROP privilege. Notes DROP SEQUENCE only removes sequences, not tables. However, DROP TABLE can remove both sequences and tables. URL: https://mariadb.com/kb/en/drop-sequence/https://mariadb.com/kb/en/drop-sequence/ &'DROP SERVERSyntax ------ DROP SERVER [ IF EXISTS ] server_name Description ----------- Drops the server definition for the server named server_name. The corresponding row within the mysql.servers table will be deleted. This statement requires the SUPER privilege. Dropping a server for a table does not affect any FederatedX, FEDERATED or Spider tables that used this connection information when they were created. IF EXISTS If the IF EXISTS clause is used, MariaDB will not return an error if the server does not exist. Unlike all other statements, DROP SERVER IF EXISTS does not issue a note if the server does not exist. See MDEV-9400. Examples -------- DROP SERVER s; IF EXISTS: DROP SERVER s; ERROR 1477 (HY000): The foreign server name you are trying to reference does not exist. Data source error: s DROP SERVER IF EXISTS s; Query OK, 0 rows affected (0.00 sec) URL: https://mariadb.com/kb/en/drop-server/https://mariadb.com/kb/en/drop-server/ ''DROP TRIGGERSyntax ------ DROP TRIGGER [IF EXISTS] [schema_name.]trigger_name Description ----------- This statement drops a trigger. The schema (database) name is optional. If the schema is omitted, the trigger is dropped from the default schema. Its use requires the TRIGGER privilege for the table associated with the trigger. Use IF EXISTS to prevent an error from occurring for a trigger that does not exist. A NOTE is generated for a non-existent trigger when using IF EXISTS. See SHOW WARNINGS. Note: Triggers for a table are also dropped if you drop the table. Examples -------- DROP TRIGGER test.example_trigger; Using the IF EXISTS clause: DROP TRIGGER IF EXISTS test.example_trigger; Query OK, 0 rows affected, 1 warning (0.01 sec) SHOW WARNINGS; +-------+------+------------------------+ | Level | Code | Message | +-------+------+------------------------+ | Note | 1360 | Trigger does not exist | +-------+------+------------------------+ URL: https://mariadb.com/kb/en/drop-trigger/https://mariadb.com/kb/en/drop-trigger/}2  ~  %'DROP TABLESyntax ------ DROP [TEMPORARY] TABLE [IF EXISTS] [/*COMMENT TO SAVE*/] tbl_name [, tbl_name] ... [WAIT n|NOWAIT] [RESTRICT | CASCADE] Description ----------- DROP TABLE removes one or more tables. You must have the DROP privilege for each table. All table data and the table definition are removed, as well as triggers associated to the table, so be careful with this statement! If any of the tables named in the argument list do not exist, MariaDB returns an error indicating by name which non-existing tables it was unable to drop, but it also drops all of the tables in the list that do exist. Important: When a table is dropped, user privileges on the table are not automatically dropped. See GRANT. If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables. Note that for a partitioned table, DROP TABLE permanently removes the table definition, all of its partitions, and all of the data which was stored in those partitions. It also removes the partitioning definition (.par) file associated with the dropped table. For each referenced table, DROP TABLE drops a temporary table with that name, if it exists. If it does not exist, and the TEMPORARY keyword is not used, it drops a non-temporary table with the same name, if it exists. The TEMPORARY keyword ensures that a non-temporary table will not accidentally be dropped. Use IF EXISTS to prevent an error from occurring for tables that do not exist. A NOTE is generated for each non-existent table when using IF EXISTS. See SHOW WARNINGS. If a foreign key references this table, the table cannot be dropped. In this case, it is necessary to drop the foreign key first. RESTRICT and CASCADE are allowed to make porting from other database systems easier. In MariaDB, they do nothing. Since MariaDB 5.5.27, the comment before the tablenames (that /*COMMENT TO SAVE*/) is stored in the binary log. That feature can be used by replication tools to send their internal messages. It is possible to specify table names as db_name.tab_name. This is useful to delete tables from multiple databases with one statement. See Identifier Qualifiers for details. The DROP privilege is required to use DROP TABLE on non-temporary tables. For temporary tables, no privilege is required, because such tables are only visible for the current session. Note: DROP TABLE automatically commits the current active transaction, unless you use the TEMPORARY keyword. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. DROP TABLE in replication DROP TABLE has the following characteristics in replication: DROP TABLE IF EXISTS are always logged. DROP TABLE without IF EXISTS for tables that don't exist are not written to the binary log. Dropping of TEMPORARY tables are prefixed in the log with TEMPORARY. These drops are only logged when running statement or mixed mode replication. One DROP TABLE statement can be logged with up to 3 different DROP statements: DROP TEMPORARY TABLE list_of_non_transactional_temporary_tables DROP TEMPORARY TABLE list_of_transactional_temporary_tables DROP TABLE list_of_normal_tables Starting from MariaDB 10.0.8, DROP TABLE on the master is treated on the slave as DROP TABLE IF EXISTS. You can change that by setting slave-ddl-exec-mode to STRICT. Dropping an Internal #sql-... Table If the mysqld process is killed during an ALTER TABLE you may find a table named #sql-... in your data directory. In MariaDB 10.3, InnoDB tables with this prefix will de deleted automatically during startup. In MariaDB 10.4 we will ensure that these temporary tables will always be deleted automatically. If you want to delete one of these tables explicitly you can do so by using the following syntax: DROP TABLE `#mysql50##sql-...`; When running an ALTER TABLE…ALGORITHM=INPLACE that rebuilds the table, InnoDB will create an internal #sql-ib table. For these tables, the .frm file will be called something else. In order to drop such a table after a server crash, you must rename the #sql*.frm file to match the #sql-ib*.ibd file. Dropping All Tables in a Database The best way to drop all tables in a database is by executing DROP DATABASE, which will drop the database itself, and all tables in it. However, if you want to drop all tables in the database, but you also want to keep the database itself and any other non-table objects in it, then you would need to execute DROP TABLE to drop each individual table. You can construct these DROP TABLE commands by querying the TABLES table in the information_schema database. For example: SELECT CONCAT('DROP TABLE IF EXISTS `', TABLE_SCHEMA, '`.`', TABLE_NAME, '`;') FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'mydb'; Examples -------- DROP TABLE Employees, Customers; Notes Beware that DROP TABLE can drop both tables and sequences. This is mainly done to allow old tools like mysqldump to work with sequences. URL: https://mariadb.com/kb/en/drop-table/https://mariadb.com/kb/en/drop-table/ BG  $'DROP VIEWSyntax ------ DROP VIEW [IF EXISTS] view_name [, view_name] ... [RESTRICT | CASCADE] Description ----------- DROP VIEW removes one or more views. You must have the DROP privilege for each view. If any of the views named in the argument list do not exist, MariaDB returns an error indicating by name which non-existing views it was unable to drop, but it also drops all of the views in the list that do exist. The IF EXISTS clause prevents an error from occurring for views that don't exist. When this clause is given, a NOTE is generated for each non-existent view. See SHOW WARNINGS. RESTRICT and CASCADE, if given, are parsed and ignored. It is possible to specify view names as db_name.view_name. This is useful to delete views from multiple databases with one statement. See Identifier Qualifiers for details. The DROP privilege is required to use DROP TABLE on non-temporary tables. For temporary tables, no privilege is required, because such tables are only visible for the current session. If a view references another view, it will be possible to drop the referenced view. However, the other view will reference a view which does not exist any more. Thus, querying it will produce an error similar to the following: ERROR 1356 (HY000): View 'db_name.view_name' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them This problem is reported in the output of CHECK TABLE. Note that it is not necessary to use DROP VIEW to replace an existing view, because CREATE VIEW has an OR REPLACE clause. Examples -------- DROP VIEW v,v2; Given views v and v2, but no view v3 DROP VIEW v,v2,v3; ERROR 1051 (42S02): Unknown table 'v3' DROP VIEW IF EXISTS v,v2,v3; Query OK, 0 rows affected, 1 warning (0.01 sec) SHOW WARNINGS; +-------+------+-------------------------+ | Level | Code | Message | +-------+------+-------------------------+ | Note | 1051 | Unknown table 'test.v3' | +-------+------+-------------------------+ URL: https://mariadb.com/kb/en/drop-view/https://mariadb.com/kb/en/drop-view/ ,'Invisible ColumnsInvisible columns (sometimes also called hidden columns) first appeared in MariaDB 10.3.3. Columns can be given an INVISIBLE attribute in a CREATE TABLE or ALTER TABLE statement. These columns will then not be listed in the results of a SELECT * statement, nor do they need to be assigned a value in an INSERT statement, unless INSERT explicitly mentions them by name. Since SELECT * does not return the invisible columns, new tables or views created in this manner will have no trace of the invisible columns. If specifically referenced in the SELECT statement, the columns will be brought into the view/new table, but the INVISIBLE attribute will not. Invisible columns can be declared as NOT NULL, but then require a DEFAULT value. It is not possible for all columns in a table to be invisible. Examples -------- CREATE TABLE t (x INT, y INT INVISIBLE, z INT INVISIBLE NOT NULL); ERROR 4106 (HY000): Invisible column `z` must have a default value CREATE TABLE t (x INT, y INT INVISIBLE, z INT INVISIBLE NOT NULL DEFAULT 4); INSERT INTO t VALUES (1),(2); INSERT INTO t (x,y) VALUES (3,33); SELECT * FROM t; +------+ | x | +------+ | 1 | | 2 | | 3 | +------+ SELECT x,y,z FROM t; +------+------+---+ | x | y | z | +------+------+---+ | 1 | NULL | 4 | | 2 | NULL | 4 | | 3 | 33 | 4 | +------+------+---+ DESC t; +-------+---------+------+-----+---------+-----------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-----------+ | x | int(11) | YES | | NULL | | | y | int(11) | YES | | NULL | INVISIBLE | | z | int(11) | NO | | 4 | INVISIBLE | +-------+---------+------+-----+---------+-----------+ ALTER TABLE t MODIFY x INT INVISIBLE, MODIFY y INT, MODIFY z INT NOT NULL DEFAULT 4; DESC t; +-------+---------+------+-----+---------+-----------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-----------+ | x | int(11) | YES | | NULL | INVISIBLE | | y | int(11) | YES | | NULL | | | z | int(11) | NO | | 4 | | +-------+---------+------+-----+---------+-----------+ Creating a view from a table with hidden columns: CREATE VIEW v1 AS SELECT * FROM t; DESC v1; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | x | int(11) | YES | | NULL | | +-------+---------+------+-----+---------+-------+ CREATE VIEW v2 AS SELECT x,y,z FROM t; DESC v2; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | x | int(11) | YES | | NULL | | | y | int(11) | YES | | NULL | | | z | int(11) | NO | | 4 | | +-------+---------+------+-----+---------+-------+ URL: https://mariadb.com/kb/en/invisible-columns/https://mariadb.com/kb/en/invisible-columns/Kb ?O^3 'MERGEDescription ----------- The MERGE storage engine, also known as the MRG_MyISAM engine, is a collection of identical MyISAM tables that can be used as one. "Identical" means that all tables have identical column and index information. You cannot merge MyISAM tables in which the columns are listed in a different order, do not have exactly the same columns, or have the indexes in different order. However, any or all of the MyISAM tables can be compressed with myisampack. Columns names and indexes names can be different, as long as data types and NULL/NOT NULL clauses are the same. Differences in table options such as AVG_ROW_LENGTH, MAX_ROWS, or PACK_KEYS do not matter. Each index in a MERGE table must match an index in underlying MyISAM tables, but the opposite is not true. Also, a MERGE table cannot have a PRIMARY KEY or UNIQUE indexes, because it cannot enforce uniqueness over all underlying tables. The following options are meaningful for MERGE tables: UNION. This option specifies the list of the underlying MyISAM tables. The list is enclosed between parentheses and separated with commas. INSERT_METHOD. This options specifies whether, and how, INSERTs are allowed for the table. Allowed values are: NO (INSERTs are not allowed), FIRST (new rows will be written into the first table specified in the UNION list), LAST (new rows will be written into the last table specified in the UNION list). The default value is NO. If you define a MERGE table with a definition which is different from the underlying MyISAM tables, or one of the underlying tables is not MyISAM, the CREATE TABLE statement will not return any error. But any statement which involves the table will produce an error like the following: ERROR 1168 (HY000): Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist A CHECK TABLE will show more information about the problem. The error is also produced if the table is properly define, but an underlying table's definition changes at some point in time. If you try to insert a new row into a MERGE table with INSERT_METHOD=NO, you will get an error like the following: ERROR 1036 (HY000): Table 'tbl_name' is read only It is possible to build a MERGE table on MyISAM tables which have one or more virtual columns. MERGE itself does not support virtual columns, thus such columns will be seen as regular columns. The data types and sizes will still need to be identical, and they cannot be NOT NULL. Examples -------- CREATE TABLE t1 ( a INT NOT NULL AUTO_INCREMENT PRIMARY KEY, message CHAR(20)) ENGINE=MyISAM; CREATE TABLE t2 ( a INT NOT NULL AUTO_INCREMENT PRIMARY KEY, message CHAR(20)) ENGINE=MyISAM; INSERT INTO t1 (message) VALUES ('Testing'),('table'),('t1'); INSERT INTO t2 (message) VALUES ('Testing'),('table'),('t2'); CREATE TABLE total ( a INT NOT NULL AUTO_INCREMENT, message CHAR(20), INDEX(a)) ENGINE=MERGE UNION=(t1,t2) INSERT_METHOD=LAST; SELECT * FROM total; +---+---------+ | a | message | +---+---------+ | 1 | Testing | | 2 | table | | 3 | t1 | | 1 | Testing | | 2 | table | | 3 | t2 | +---+---------+ In the following example, we'll create three MyISAM tables, and then a MERGE table on them. However, one of them uses a different data type for the column b, so a SELECT will produce an error: CREATE TABLE t1 ( a INT, b INT ) ENGINE = MyISAM; CREATE TABLE t2 ( a INT, b INT ) ENGINE = MyISAM; CREATE TABLE t3 ( a INT, b TINYINT ) ENGINE = MyISAM; CREATE TABLE t_mrg ( a INT, b INT ) ENGINE = MERGE,UNION=(t1,t2,t3); SELECT * FROM t_mrg; ERROR 1168 (HY000): Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist To find out what's wrong, we'll use a CHECK TABLE: CHECK TABLE t_mrg; +------------+-------+----------+-----------------------------------------------------------------------------------------------------+ | Table | Op | Msg_type | Msg_text | +------------+-------+----------+-----------------------------------------------------------------------------------------------------+ | test.t_mrg | check | Error | Table 'test.t3' is differently defined or of non-MyISAM type or doesn't exist | | test.t_mrg | check | Error | Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist | | test.t_mrg | check | error | Corrupt | +------------+-------+----------+-----------------------------------------------------------------------------------------------------+ Now, we know that the problem is in t3's definition. URL: https://mariadb.com/kb/en/merge/https://mariadb.com/kb/en/merge/ "''RENAME TABLESyntax ------ RENAME TABLE tbl_name [WAIT n | NOWAIT] TO new_tbl_name [, tbl_name2 TO new_tbl_name2] ... Description ----------- This statement renames one or more tables or views, but not the privileges associated to them. The rename operation is done atomically, which means that no other session can access any of the tables while the rename is running. For example, if you have an existing table old_table, you can create another table new_table that has the same structure but is empty, and then replace the existing table with the empty one as follows (assuming that backup_table does not already exist): CREATE TABLE new_table (...); RENAME TABLE old_table TO backup_table, new_table TO old_table; tbl_name can optionally be specified as db_name.tbl_name. See Identifier Qualifiers. This allows to use RENAME to move a table from a database to another (as long as they are on the same filesystem): RENAME TABLE db1.t TO db2.t; Note that moving a table to another database is not possible if it has some triggers. Trying to do so produces the following error: ERROR 1435 (HY000): Trigger in wrong schema Also, views cannot be moved to another database: ERROR 1450 (HY000): Changing schema from 'old_db' to 'new_db' is not allowed. If a RENAME TABLE renames more than one table and one renaming fails, all renames executed by the same statement are rolled back. Renames are always executed in the specified order. Knowing this, it is also possible to swap two tables' names: RENAME TABLE t1 TO tmp_table, t2 TO t1, tmp_table TO t2; Privileges Executing the RENAME TABLE statement requires the DROP, CREATE and INSERT privileges for the table or the database. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. URL: https://mariadb.com/kb/en/rename-table/https://mariadb.com/kb/en/rename-table/^c R  O 0'Silent Column ChangesWhen a CREATE TABLE or ALTER TABLE command is issued, MariaDB will silently change a column specification in the following cases: PRIMARY KEY columns are always NOT NULL. Any trailing spaces from SET and ENUM values are discarded. TIMESTAMP columns are always NOT NULL, and display sizes are discarded A row-size limit of 65535 bytes applies If strict SQL mode is not enabled, a VARCHAR column longer than 65535 become TEXT, and a VARBINARY columns longer than 65535 becomes a BLOB. If strict mode is enabled the silent changes will not be made, and an error will occur. If a USING clause specifies an index that's not permitted by the storage engine, the engine will instead use another available index type that can be applied without affecting results. If the CHARACTER SET binary attribute is specified, the column is created as the matching binary data type. A TEXT becomes a BLOB, CHAR a BINARY and VARCHAR a VARBINARY. ENUMs and SETs are created as defined. To ease imports from other RDBMS's, MariaDB will also silently map the following data types: Other Vendor Type | MariaDB Type | BOOL | TINYINT | BOOLEAN | TINYINT | CHARACTER VARYING(M) | VARCHAR(M) | FIXED | DECIMAL | FLOAT4 | FLOAT | FLOAT8 | DOUBLE | INT1 | TINYINT | INT2 | SMALLINT | INT3 | MEDIUMINT | INT4 | INT | INT8 | BIGINT | LONG VARBINARY | MEDIUMBLOB | LONG VARCHAR | MEDIUMTEXT | LONG | MEDIUMTEXT | MIDDLEINT | MEDIUMINT | NUMERIC | DECIMAL | Currently, all MySQL types are supported in MariaDB. For type mapping between Cassandra and MariaDB, see Cassandra storage engine. Example Silent changes in action: CREATE TABLE SilenceIsGolden ( f1 TEXT CHARACTER SET binary, f2 VARCHAR(15) CHARACTER SET binary, f3 CHAR CHARACTER SET binary, f4 ENUM('x','y','z') CHARACTER SET binary, f5 VARCHAR (65536), f6 VARBINARY (65536), f7 INT1 ); Query OK, 0 rows affected, 2 warnings (0.31 sec) SHOW WARNINGS; +-------+------+-----------------------------------------------+ | Level | Code | Message | +-------+------+-----------------------------------------------+ | Note | 1246 | Converting column 'f5' from VARCHAR to TEXT | | Note | 1246 | Converting column 'f6' from VARBINARY to BLOB | +-------+------+-----------------------------------------------+ DESCRIBE SilenceIsGolden; +-------+-------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------------+------+-----+---------+-------+ | f1 | blob | YES | | NULL | | | f2 | varbinary(15) | YES | | NULL | | | f3 | binary(1) | YES | | NULL | | | f4 | enum('x','y','z') | YES | | NULL | | | f5 | mediumtext | YES | | NULL | | | f6 | mediumblob | YES | | NULL | | | f7 | tinyint(4) | YES | | NULL | | +-------+-------------------+------+-----+---------+-------+ URL: https://mariadb.com/kb/en/silent-column-changes/https://mariadb.com/kb/en/silent-column-changes/7(NEXT VALUE for sequence_nameSEQUENCEs were introduced in MariaDB 10.3 Syntax ------ NEXT VALUE FOR sequence or NEXTVAL(sequence_name) or in Oracle mode (SQL_MODE=ORACLE) sequence_name.nextval NEXT VALUE FOR is ANSI SQL syntax while NEXTVAL() is PostgreSQL syntax. Description ----------- Generate next value for a SEQUENCE. You can greatly speed up NEXT VALUE by creating the sequence with the CACHE option. If not, every NEXT VALUE usage will cause changes in the stored SEQUENCE table. When using NEXT VALUE the value will be reserved at once and will not be reused, except if the SEQUENCE was created with CYCLE. This means that when you are using SEQUENCEs you have to expect gaps in the generated sequence numbers. If one updates the SEQUENCE with SETVAL() or ALTER SEQUENCE ... RESTART, NEXT VALUE FOR will notice this and start from the next requested value. FLUSH TABLES will close the sequence and the next sequence number generated will be according to what's stored in the SEQUENCE object. In effect, this will discard the cached values. NEXT VALUE requires the INSERT privilege. You can also use NEXT VALUE FOR sequence for column DEFAULT. URL: https://mariadb.com/kb/en/next-value-for-sequence_name/https://mariadb.com/kb/en/next-value-for-sequence_name/ ;(PREVIOUS VALUE FOR sequence_nameSEQUENCEs were introduced in MariaDB 10.3. Syntax ------ PREVIOUS VALUE FOR sequence_name or LASTVAL(sequence_name) or in Oracle mode (SQL_MODE=ORACLE) sequence_name.currval PREVIOUS VALUE FOR is IBM DB2 syntax while LASTVAL() is PostgreSQL syntax. Description ----------- Get last value in the current connection generated from a sequence. If the sequence has not yet been used by the connection, PREVIOUS VALUE FOR returns NULL If a SEQUENCE has been dropped and re-created then it's treated as a new SEQUENCE and PREVIOUS VALUE FOR will return NULL. FLUSH TABLES has no effect on PREVIOUS VALUE FOR. Previous values for all used sequences are stored per connection until connection ends. PREVIOUS VALUE FOR requires the SELECT privilege. Example SELECT PREVIOUS VALUE FOR s; +----------------------+ | PREVIOUS VALUE FOR s | +----------------------+ | 100 | +----------------------+ URL: https://mariadb.com/kb/en/previous-value-for-sequence_name/https://mariadb.com/kb/en/previous-value-for-sequence_name/;  ʼ)'TRUNCATE TABLESyntax ------ TRUNCATE [TABLE] tbl_name [WAIT n | NOWAIT] Description ----------- TRUNCATE TABLE empties a table completely. It requires the DROP privilege. See GRANT. tbl_name can also be specified in the form db_name.tbl_name (see Identifier Qualifiers). Logically, TRUNCATE TABLE is equivalent to a DELETE statement that deletes all rows, but there are practical differences under some circumstances. TRUNCATE TABLE will fail for an InnoDB table if any FOREIGN KEY constraints from other tables reference the table, returning the error: ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key constraint Foreign Key constraints between columns in the same table are permitted. For an InnoDB table, if there are no FOREIGN KEY constraints, InnoDB performs fast truncation by dropping the original table and creating an empty one with the same definition, which is much faster than deleting rows one by one. The AUTO_INCREMENT counter is reset by TRUNCATE TABLE, regardless of whether there is a FOREIGN KEY constraint. The count of rows affected by TRUNCATE TABLE is accurate only when it is mapped to a DELETE statement. For other storage engines, TRUNCATE TABLE differs from DELETE in the following ways: Truncate operations drop and re-create the table, which is much faster than deleting rows one by one, particularly for large tables. Truncate operations cause an implicit commit. Truncation operations cannot be performed if the session holds an active table lock. Truncation operations do not return a meaningful value for the number of deleted rows. The usual result is "0 rows affected," which should be interpreted as "no information." As long as the table format file tbl_name.frm is valid, the table can be re-created as an empty table with TRUNCATE TABLE, even if the data or index files have become corrupted. The table handler does not remember the last used AUTO_INCREMENT value, but starts counting from the beginning. This is true even for MyISAM and InnoDB, which normally do not reuse sequence values. When used with partitioned tables, TRUNCATE TABLE preserves the partitioning; that is, the data and index files are dropped and re-created, while the partition definitions (.par) file is unaffected. Since truncation of a table does not make any use of DELETE, the TRUNCATE statement does not invoke ON DELETE triggers. TRUNCATE TABLE will only reset the values in the Performance Schema summary tables to zero or null, and will not remove the rows. For the purposes of binary logging and replication, TRUNCATE TABLE is treated as DROP TABLE followed by CREATE TABLE (DDL rather than DML). TRUNCATE TABLE does not work on views. Currently, TRUNCATE TABLE drops all historical records from a system-versioned table. WAIT/NOWAIT Set the lock wait timeout. See WAIT and NOWAIT. Oracle-mode Oracle-mode from MariaDB 10.3 permits the optional keywords REUSE STORAGE or DROP STORAGE to be used. TRUNCATE [TABLE] tbl_name [{DROP | REUSE} STORAGE] These have no effect on the operation. Performance TRUNCATE TABLE is faster than DELETE, because it drops and re-creates a table. With XtraDB/InnoDB, TRUNCATE TABLE is slower if innodb_file_per_table=ON is set (the default since MariaDB 5.5). This is because TRUNCATE TABLE unlinks the underlying tablespace file, which can be an expensive operation. See MDEV-8069 for more details. The performance issues with innodb_file_per_table=ON can be exacerbated in cases where the InnoDB buffer pool is very large and innodb_adaptive_hash_index=ON is set. In that case, using DROP TABLE followed by CREATE TABLE instead of TRUNCATE TABLE may perform better. Setting innodb_adaptive_hash_index=OFF can also help. In MariaDB 10.2.19 and later, this performance can also be improved by setting innodb_safe_truncate=OFF. See MDEV-9459 for more details. Setting innodb_adaptive_hash_index=OFF can also improve TRUNCATE TABLE performance in general. See MDEV-16796 for more details. URL: https://mariadb.com/kb/en/truncate-table/https://mariadb.com/kb/en/truncate-table/-?H)Differences between JSON_QUERY and JSON_VALUEJSON functions were added in MariaDB 10.2.3. The primary difference between the two functions is that JSON_QUERY returns an object or an array, while JSON_VALUE returns a scalar. Take the following JSON document as an example SET @json='{ "x": [0,1], "y": "[0,1]", "z": "Monty" }'; Note that data member "x" is an array, and data members "y" and "z" are strings. The following examples demonstrate the differences between the two functions. SELECT JSON_QUERY(@json,'$'), JSON_VALUE(@json,'$'); +--------------------------------------------+-----------------------+ | JSON_QUERY(@json,'$') | JSON_VALUE(@json,'$') | +--------------------------------------------+-----------------------+ | { "x": [0,1], "y": "[0,1]", "z": "Monty" } | NULL | +--------------------------------------------+-----------------------+ SELECT JSON_QUERY(@json,'$.x'), JSON_VALUE(@json,'$.x'); +-------------------------+-------------------------+ | JSON_QUERY(@json,'$.x') | JSON_VALUE(@json,'$.x') | +-------------------------+-------------------------+ | [0,1] | NULL | +-------------------------+-------------------------+ SELECT JSON_QUERY(@json,'$.y'), JSON_VALUE(@json,'$.y'); +-------------------------+-------------------------+ | JSON_QUERY(@json,'$.y') | JSON_VALUE(@json,'$.y') | +-------------------------+-------------------------+ | NULL | [0,1] | +-------------------------+-------------------------+ SELECT JSON_QUERY(@json,'$.z'), JSON_VALUE(@json,'$.z'); +-------------------------+-------------------------+ | JSON_QUERY(@json,'$.z') | JSON_VALUE(@json,'$.z') | +-------------------------+-------------------------+ | NULL | Monty | +-------------------------+-------------------------+ SELECT JSON_QUERY(@json,'$.x[0]'), JSON_VALUE(@json,'$.x[0]'); +----------------------------+----------------------------+ | JSON_QUERY(@json,'$.x[0]') | JSON_VALUE(@json,'$.x[0]') | +----------------------------+----------------------------+ | NULL | 0 | +----------------------------+----------------------------+ URL: https://mariadb.com/kb/en/differences-between-json_query-and-json_value/https://mariadb.com/kb/en/differences-between-json_query-and-json_value/- !s,MSyntax ------ [GENERATED ALWAYS] AS ( ) [VIRTUAL | PERSISTENT | STORED] [UNIQUE] [UNIQUE KEY] [COMMENT ] MariaDB's generated columns syntax is designed to be similar to the syntax for Microsoft SQL Server's computed columns and Oracle Database's virtual columns. In MariaDB 10.2 and later, the syntax is also compatible with the syntax for MySQL's generated columns. Description ----------- A generated column is a column in a table that cannot explicitly be set to a specific value in a DML query. Instead, its value is automatically generated based on an expression. This expression might generate the value based on the values of other columns in the table, or it might generate the value by calling built-in functions or user-defined functions (UDFs). There are two types of generated columns: PERSISTENT or STORED: This type's value is actually stored in the table. VIRTUAL: This type's value is not stored at all. Instead, the value is generated dynamically when the table is queried. This type is the default. Generated columns are also sometimes called computed columns or virtual columns. Supported Features Storage Engine Support Generated columns can only be used with storage engines which support them. If you try to use a storage engine that does not support them, then you will see an error similar to the following: ERROR 1910 (HY000): TokuDB storage engine does not support computed columns InnoDB, Aria, MyISAM and CONNECT support generated columns. A column in a MERGE table can be built on a PERSISTENT generated column. However, a column in a MERGE table can not be defined as a VIRTUAL and PERSISTENT generated column. Data Type Support All data types are supported when defining generated columns. Using the ZEROFILL column option is supported when defining generated columns. In MariaDB 10.2.6 and later, the following statements apply to data types for generated columns: Using the AUTO_INCREMENT column option is not supported when defining generated columns. Previously, it was supported, but this support was removed, because it would not work correctly. See MDEV-11117. Index Support Using a generated column as a table's primary key is not supported. See MDEV-5590 for more information. If you try to use one as a primary key, then you will see an error similar to the following: ERROR 1903 (HY000): Primary key cannot be defined upon a computed column Using PERSISTENT generated columns as part of a foreign key is supported. Referencing PERSISTENT generated columns as part of a foreign key is also supported. However, using the ON UPDATE CASCADE, ON UPDATE SET NULL, or ON DELETE SET NULL clauses is not supported. If you try to use an unsupported clause, then you will see an error similar to the following: ERROR 1905 (HY000): Cannot define foreign key with ON UPDATE SET NULL clause on a computed column In MariaDB 10.2.3 and later, the following statements apply to indexes for generated columns: Defining indexes on both VIRTUAL and PERSISTENT generated columns is supported. If an index is defined on a generated column, then the optimizer considers using it in the same way as indexes based on "real" columns. MariaDB until 10.2.2 In MariaDB 10.2.2 and before, the following statements apply to indexes for generated columns: Defining indexes on VIRTUAL generated columns is not supported. Defining indexes on PERSISTENT generated columns is supported. If an index is defined on a generated column, then the optimizer considers using it in the same way as indexes based on "real" columns. Statement Support Generated columns are used in DML queries just as if they were "real" columns. However, VIRTUAL and PERSISTENT generated columns differ in how their data is stored. Values for PERSISTENT generated columns are generated whenever a DML queries inserts or updates the row with the special DEFAULT value. This generates the columns value, and it is stored in the table like the other "real" columns. This value can be read by other DML queries just like the other "real" columns. Values for VIRTUAL generated columns are not stored in the table. Instead, the value is generated dynamically whenever the column is queried. If other columns in a row are queried, but the VIRTUAL generated column is not one of the queried columns, then the column's value is not generated. The SELECT statement supports generated columns. Generated columns can be referenced in the INSERT, UPDATE, and DELETE statements. However, VIRTUAL or PERSISTENT generated columns cannot be explicitly set to any other values than NULL or DEFAULT. If a generated column is explicitly set to any other value, then the outcome depends on whether strict mode is enabled in SQL_MODE. If it is not enabled, then a warning will be raised and the default generated value will be used instead. If it is enabled, then an error will be raised instead. The CREATE TABLE statement has limited support for generated columns. It supports defining generated columns in a new table. It supports using generated columns to partition tables. It does not support using the versioning clauses with generated columns. The ALTER TABLE statement has limited support for generated columns. It supports the MODIFY and CHANGE clauses for PERSISTENT generated columns. It does not support the MODIFY clause for VIRTUAL generated columns if ALGORITHM is not set to COPY. See MDEV-15476 for more information. It does not support the CHANGE clause for VIRTUAL generated columns if ALGORITHM is not set to COPY. See MDEV-17035 for more information. It does not support altering a table if ALGORITHM is not set to COPY if the table has a VIRTUAL generated column that is indexed. See MDEV-14046 for more information. It does not support adding a VIRTUAL generated column with the ADD clause if the same statement is also adding other columns if ALGORITHM is not set to COPY. See MDEV-17468 for more information. It also does not support altering an existing column into a VIRTUAL generated column. It supports using generated columns to partition tables. It does not support using the versioning clauses with generated columns. The SHOW CREATE TABLE statement supports generated columns. The DESCRIBE statement can be used to check whether a table has generated columns. You can tell which columns are generated by looking for the ones where the Extra column is set to either VIRTUAL or PERSISTENT. For example: DESCRIBE table1; +-------+-------------+------+-----+---------+------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+------------+ | a | int(11) | NO | | NULL | | | b | varchar(32) | YES | | NULL | | | c | int(11) | YES | | NULL | VIRTUAL | | d | varchar(5) | YES | | NULL | PERSISTENT | +-------+-------------+------+-----+---------+------------+ Generated columns can be properly referenced in the NEW and OLD rows in triggers. Stored procedures support generated columns. The HANDLER statement supports generated columns. Expression Support Most legal, deterministic expressions which can be calculated are supported in expressions for generated columns. Most built-in functions are supported in expressions for generated columns. However, some built-in functions can't be supported for technical reasons. For example, If you try to use an unsupported function in an expression, then you will see an error similar to the following: ERROR 1901 (HY000): Function or expression 'dayname()' cannot be used in the GENERATED ALWAYS AS clause of `v` Subqueries are not supported in expressions for generated columns because the underlying data can change. Using anything that depends on data outside the row is not supported in expressions for generated columns. Stored functions are not supported in expressions for generated columns. See MDEV-17587 for more information. In MariaDB 10.2.1 and later, the following statements apply to expressions for generated columns: Non-deterministic built-in functions are supported in expressions for PERSISTENT generated columns. If a non-deterministic function is used for a PERSISTENT generated column, th*Ben any changes made to this table should be logged to the binary log in the row-based logging format when the binlog_format system variable is set to MIXED. However, this does not always happen. Therefore, it is recommended to set the binlog_format system variable to ROW. See MDEV-10436 for more information. Non-deterministic built-in functions are not supported in expressions for VIRTUAL generated columns. User-defined functions (UDFs) are supported in expressions for generated columns. However, MariaDB can't check whether a UDF is deterministic, so it is up to the user to be sure that they do not use non-deterministic UDFs with VIRTUAL generated columns. Defining a generated column based on other generated columns defined before it in the table definition is supported. For example: CREATE TABLE t1 (a int as (1), b int as (a)); However, defining a generated column based on other generated columns defined after in the table definition is not supported in expressions for generation columns because generated columns are calculated in the order they are defined. Using an expression that exceeds 255 characters in length is supported in expressions for generated columns. The new limit for the entire table definition, including all expressions for generated columns, is 65,535 bytes. Using constant expressions is supported in expressions for generated columns. For example: CREATE TABLE t1 (a int as (1)); MariaDB until 10.2.0 In MariaDB 10.2.0 and before, the following statements apply to expressions for generated columns: Non-deterministic built-in functions are not supported in expressions for generated columns. User-defined functions (UDFs) are not supported in expressions for generated columns. Defining a generated column based on other generated columns defined in the table is not supported. Otherwise, it would generate errors like this: ERROR 1900 (HY000): A computed column cannot be based on a computed column Using an expression that exceeds 255 characters in length is not supported in expressions for generated columns. Using constant expressions is not supported in expressions for generated columns. Otherwise, it would generate errors like this: ERROR 1908 (HY000): Constant expression in computed column function is not allowed MySQL Compatibility Support In MariaDB 10.2.1 and later, the following statements apply to MySQL compatibility for generated columns: The STORED keyword is supported as an alias for the PERSISTENT keyword. Tables created with MySQL 5.7 or later that contain MySQL's generated columns can be imported into MariaDB without a dump and restore. MariaDB until 10.2.0 In MariaDB 10.2.0 and before, the following statements apply to MySQL compatibility for generated columns: The STORED keyword is not supported as an alias for the PERSISTENT keyword. Tables created with MySQL 5.7 or later that contain MySQL's generated columns can not be imported into MariaDB without a dump and restore. Implementation Differences Generated columns are subject to various constraints in other DBMSs that are not present in MariaDB's implementation. Generated columns may also be called computed columns or virtual columns in different implementations. The various details for a specific implementation can be found in the documentation for each specific DBMS. Implementation Differences Compared to Microsoft SQL Server MariaDB's generated columns implementation does not enforce the following restrictions that are present in Microsoft SQL Server's computed columns implementation: MariaDB allows server variables in generated column expressions, including those that change dynamically, such as warning_count. MariaDB allows the CONVERT_TZ() function to be called with a named time zone as an argument, even though time zone names and time offsets are configurable. MariaDB allows the CAST() function to be used with non-unicode character sets, even though character sets are configurable and differ between binaries/versions. MariaDB allows FLOAT expressions to be used in generated columns. Microsoft SQL Server considers these expressions to be "imprecise" due to potential cross-platform differences in floating-point implementations and precision. Microsoft SQL Server requires the ARITHABORT mode to be set, so that division by zero returns an error, and not a NULL. Microsoft SQL Server requires QUOTED_IDENTIFIER to be set in SQL_MODE. In MariaDB, if data is inserted without ANSI_QUOTES set in SQL_MODE, then it will be processed and stored differently in a generated column that contains quoted identifiers. In MariaDB 10.2.0 and before, it does not allow user-defined functions (UDFs) to be used in expressions for generated columns. Microsoft SQL Server enforces the above restrictions by doing one of the following things: Refusing to create computed columns. Refusing to allow updates to a table containing them. Refusing to use an index over such a column if it can not be guaranteed that the expression is fully deterministic. In MariaDB, as long as the SQL_MODE, language, and other settings that were in effect during the CREATE TABLE remain unchanged, the generated column expression will always be evaluated the same. If any of these things change, then please be aware that the generated column expression might not be evaluated the same way as it previously was. In MariaDB 5.2, you will get a warning if you try to update a virtual column. In MariaDB 5.3 and later, this warning will be converted to an error if strict mode is enabled in SQL_MODE. Development History Generated columns was originally developed by Andrey Zhakov. It was then modified by Sanja Byelkin and Igor Babaev at Monty Program for inclusion in MariaDB. Monty did the work on MariaDB 10.2 to lift a some of the old limitations. Examples -------- Here is an example table that uses both VIRTUAL and PERSISTENT virtual columns: USE TEST; CREATE TABLE table1 ( a INT NOT NULL, b VARCHAR(32), c INT AS (a mod 10) VIRTUAL, d VARCHAR(5) AS (left(b,5)) PERSISTENT); If you describe the table, you can easily see which columns are virtual by looking in the "Extra" column: DESCRIBE table1; +-------+-------------+------+-----+---------+------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+------------+ | a | int(11) | NO | | NULL | | | b | varchar(32) | YES | | NULL | | | c | int(11) | YES | | NULL | VIRTUAL | | d | varchar(5) | YES | | NULL | PERSISTENT | +-------+-------------+------+-----+---------+------------+ To find out what function(s) generate the value of the virtual column you can use SHOW CREATE TABLE: SHOW CREATE TABLE table1; | table1 | CREATE TABLE `table1` ( `a` int(11) NOT NULL, `b` varchar(32) DEFAULT NULL, `c` int(11) AS (a mod 10) VIRTUAL, `d` varchar(5) AS (left(b,5)) PERSISTENT ) ENGINE=MyISAM DEFAULT CHARSET=latin1 | If you try to insert non-default values into a virtual column, you will receive a warning and what you tried to insert will be ignored and the derived value inserted instead: WARNINGS; Show warnings enabled. INSERT INTO table1 VALUES (1, 'some text',default,default); Query OK, 1 row affected (0.00 sec) INSERT INTO table1 VALUES (2, 'more text',5,default); Query OK, 1 row affected, 1 warning (0.00 sec) Warning (Code 1645): The value specified for computed column 'c' in table 'table1' has been ignored. INSERT INTO table1 VALUES (123, 'even more text',default,'something'); Query OK, 1 row affected, 2 warnings (0.00 sec) Warning (Code 1645): The value specified for computed column 'd' in table 'table1' has been ignored. Warning (Code 1265): Data truncated for column 'd' at row 1 SELECT * FROM table1; +-----+----------------+------+-------+ | a | b | c | d | +-----+----------------+------+-------+ | 1 | some text | 1 | some | | 2 | more text | 2 | more | | 123 | even more text | 3 | even | +-----+----------------+------+-------+ 3 rows in set (0.00 sec) If the ZEROFILL clause is specified, it should be placed directly after the type definition, before the AS (): CREATE TABLE table2 (a INT, b INT ZEROFILL AS (a*2) VIRTU,(Sequence OverviewSequences were introduced in MariaDB 10.3. Introduction A sequence is an object that generates a sequence of numeric values, as specified by the CREATE SEQUENCE statement. CREATE SEQUENCE will create a sequence that generates new values when called with NEXT VALUE FOR sequence_name. It's an alternative to AUTO INCREMENT when one wants to have more control of how the numbers are generated. As the SEQUENCE caches values (up to the CACHE value in the CREATE SEQUENCE statement, by default 1000) it can in some cases be much faster than AUTO INCREMENT. Another benefit is that one can access the last value generated by all used sequences, which solves one of the limitations with LAST_INSERT_ID(). Creating a Sequence The CREATE SEQUENCE statement is used to create a sequence. Here is an example of a sequence starting at 100, incrementing by 10 each time: CREATE SEQUENCE s START WITH 100 INCREMENT BY 10; The CREATE SEQUENCE statement, along with defaults, can be viewd with the SHOW CREATE SEQUENCE STATEMENT, for example: SHOW CREATE SEQUENCE s\G *************************** 1. row *************************** Table: s Create Table: CREATE SEQUENCE `s` start with 100 minvalue 1 maxvalue 9223372036854775806 increment by 10 cache 1000 nocycle ENGINE=InnoDB Using Sequence Objects To get the next value from a sequence, use NEXT VALUE FOR sequence_name or NEXTVAL(sequence_name) or in Oracle mode (SQL_MODE=ORACLE) sequence_name.nextval For retrieving the last value used by the current connection from a sequence use: PREVIOUS VALUE FOR sequence_name or LASTVAL(sequence_name) or in Oracle mode (SQL_MODE=ORACLE) sequence_name.currval For example: SELECT NEXTVAL(s); +------------+ | NEXTVAL(s) | +------------+ | 100 | +------------+ SELECT NEXTVAL(s); +------------+ | NEXTVAL(s) | +------------+ | 110 | +------------+ SELECT LASTVAL(s); +------------+ | LASTVAL(s) | +------------+ | 110 | +------------+ Using Sequences in DEFAULT Starting from 10.3.3 you can use Sequences in DEFAULT: create sequence s1; create table t1 (a int primary key default (next value for s1), b int); insert into t1 (b) values (1),(2); select * from t1; +---+------+ | a | b | +---+------+ | 1 | 1 | | 2 | 2 | +---+------+ Changing a Sequence The ALTER SEQUENCE statement is used for changing sequences. For example, to restart the sequence at another value: ALTER SEQUENCE s RESTART 50; SELECT NEXTVAL(s); +------------+ | NEXTVAL(s) | +------------+ | 50 | +------------+ The SETVAL function can also be used to set the next value to be returned for a SEQUENCE, for example: SELECT SETVAL(s, 100); +----------------+ | SETVAL(s, 100) | +----------------+ | 100 | +----------------+ SETVAL can only be used to increase the sequence value. Attempting to set a lower value will fail, returning NULL: SELECT SETVAL(s, 50); +---------------+ | SETVAL(s, 50) | +---------------+ | NULL | +---------------+ Dropping a Sequence The DROP SEQUENCE statement is used to drop a sequence, for example: DROP SEQUENCE s; Replication If one wants to use Sequences in a master-master setup or with Galera one should use INCREMENT=0. This will tell the Sequence to use auto_increment_increment and auto_increment_offset to generate unique values for each server. Standards Compliance MariaDB 10.3 supports both ANSI SQL and Oracle syntax for sequences. However as SEQUENCE is implemented as a special kind of table, it uses the same namespace as tables. The benefits are that sequences show up in SHOW TABLES, and one can also create a sequence with CREATE TABLE and drop it with DROP TABLE. One can SELECT from it as from any other table. This ensures that all old tools that work with tables should work with sequences. Since sequence objects act as regular tables in many contexts, they will be affected by LOCK TABLES. This is not the case in other DBMS, such as Oracle, where LOCK TABLE does not affect sequences. Notes One of the goals with the Sequence implementation is that all old tools, such as mysqldump, should work unchanged, while still keeping the normal usage of sequence standard compatibly. To make this possible, sequence is currently implemented as a table with a few exclusive properties. The special properties for sequence tables are: A sequence table has always one row. When one creates a sequence, either with CREATE TABLE or CREATE SEQUENCE, one row will be inserted. If one tries to insert into a sequence table, the single row will be updated. This allows mysqldump to work but also gives the additional benefit that one can change all properties of a sequence with a single insert. New applications should of course also use ALTER SEQUENCE. UPDATE or DELETE can't be performed on Sequence objects. Doing a select on the sequence shows the current state of the sequence, except the values that are reserved in the cache. The next_value column shows the next value not reserved by the cache. FLUSH TABLES will close the sequence and the next sequence number generated will be according to what's stored in the Sequence object. In effect, this will discard the cached values. A number of normal table operations work on Sequence tables. See next section. Table Operations that Work with Sequences SHOW CREATE TABLE sequence_name. This shows the table structure that is behind the SEQUENCE including the field names that can be used with SELECT or even CREATE TABLE. CREATE TABLE sequence-structure ... SEQUENCE=1 ALTER TABLE sequence RENAME TO sequence2 RENAME TABLE sequence_name TO new_sequence_name DROP TABLE sequence_name. This is allowed mainly to get old tools like mysqldump to work with sequence tables. SHOW TABLES Implementation Internally, sequence tables are created as a normal table without rollback (the InnoDB, Aria and MySAM engines support this), wrapped by a sequence engine object. This allowed us to create sequences with almost no performance impact for normal tables. (The cost is one 'if' per insert if the binary log is enabled). Underlying Table Structure The following example shows the table structure of sequences and how it can be used as a table. (Output of results are slightly edited to make them easier to read) create sequence t1; show create sequence t1\G ***** 1. row ***** CREATE SEQUENCE `t1` start with 1 minvalue 1 maxvalue 9223372036854775806 increment by 1 cache 1000 nocycle ENGINE=InnoDB show create table t1\G ***** 1. row ***** Create Table: CREATE TABLE `t1` ( `next_not_cached_value` bigint(21) NOT NULL, `minimum_value` bigint(21) NOT NULL, `maximum_value` bigint(21) NOT NULL, `start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created or value if RESTART is used', `increment` bigint(21) NOT NULL COMMENT 'increment value', `cache_size` bigint(21) unsigned NOT NULL, `cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 1 if the sequence should begin a new cycle when maximum_value is passed', `cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done' ) ENGINE=InnoDB SEQUENCE=1 select * from t1\G next_not_cached_value: 1 minimum_value: 1 maximum_value: 9223372036854775806 start_value: 1 increment: 1 cache_size: 1000 cycle_option: 0 cycle_count: 0 The cycle_count column is incremented every time the sequence wraps around. Credits Thanks to Jianwe Zhao from Aliyun for his work on SEQUENCE in AliSQL, which gave ideas and inspiration for this work. Thanks to Peter Gulutzan,who helped test and gave useful comments about the implementation. URL: https://mariadb.com/kb/en/sequence-overview/https://mariadb.com/kb/en/sequence-overview/ :Upo T !(SETVAL()SEQUENCEs were introduced in MariaDB 10.3. Syntax ------ SETVAL(sequence_name, next_value, [is_used, [round]]) Description ----------- Set the next value to be returned for a SEQUENCE. This function is compatible with PostgreSQL syntax, extended with the round argument. If the is_used argument is not given or is 1 or true, then the next used value will one after the given value. If is_used is 0 or false then the next generated value will be the given value. If round is used then it will set the round value (or the internal cycle count, starting at zero) for the sequence. If round is not used, it's assumed to be 0. next_value must be an integer literal. For SEQUENCE tables defined with CYCLE (see CREATE SEQUENCE) one should use both next_value and round to define the next value. In this case the current sequence value is defined to be round, next_value. The result returned by SETVAL() is next_value or NULL if the given next_value and round is smaller than the current value. SETVAL() will not set the SEQUENCE value to a something that is less than its current value. This is needed to ensure that SETVAL() is replication safe. If you want to set the SEQUENCE to a smaller number use ALTER SEQUENCE. If CYCLE is used, first round and then next_value are compared to see if the value is bigger than the current value. Internally, in the MariaDB server, SETVAL() is used to inform slaves that a SEQUENCE has changed value. The slave may get SETVAL() statements out of order, but this is ok as only the biggest one will have an effect. SETVAL requires the INSERT privilege. Examples -------- SELECT setval(foo, 42); -- Next nextval will return 43 SELECT setval(foo, 42, true); -- Same as above SELECT setval(foo, 42, false); -- Next nextval will return 42 SETVAL setting higher and lower values on a sequence with an increment of 10: SELECT NEXTVAL(s); +------------+ | NEXTVAL(s) | +------------+ | 50 | +------------+ SELECT SETVAL(s, 100); +----------------+ | SETVAL(s, 100) | +----------------+ | 100 | +----------------+ SELECT NEXTVAL(s); +------------+ | NEXTVAL(s) | +------------+ | 110 | +------------+ SELECT SETVAL(s, 50); +---------------+ | SETVAL(s, 50) | +---------------+ | NULL | +---------------+ SELECT NEXTVAL(s); +------------+ | NEXTVAL(s) | +------------+ | 120 | +------------+ Example demonstrating round: CREATE OR REPLACE SEQUENCE s1 START WITH 1 MINVALUE 1 MAXVALUE 99 INCREMENT BY 1 CACHE 20 CYCLE; SELECT SETVAL(s1, 99, 1, 0); +----------------------+ | SETVAL(s1, 99, 1, 0) | +----------------------+ | 99 | +----------------------+ SELECT NEXTVAL(s1); +-------------+ | NEXTVAL(s1) | +-------------+ | 1 | +-------------+ The following statement returns NULL, as the given next_value and round is smaller than the current value. SELECT SETVAL(s1, 99, 1, 0); +----------------------+ | SETVAL(s1, 99, 1, 0) | +----------------------+ | NULL | +----------------------+ SELECT NEXTVAL(s1); +-------------+ | NEXTVAL(s1) | +-------------+ | 2 | +-------------+ Increasing the round from zero to 1 will allow next_value to be returned. SELECT SETVAL(s1, 99, 1, 1); +----------------------+ | SETVAL(s1, 99, 1, 1) | +----------------------+ | 99 | +----------------------+ SELECT NEXTVAL(s1); +-------------+ | NEXTVAL(s1) | +-------------+ | 1 | +-------------+ URL: https://mariadb.com/kb/en/setval/https://mariadb.com/kb/en/setval/,)JSON_ARRAY_APPENDJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_ARRAY_APPEND(json_doc, path, value[, path, value] ...) Description ----------- Appends values to the end of the specified arrays within a JSON document, returning the result, or NULL if any of the arguments are NULL. Evaluation is performed from left to right, with the resulting document from the previous pair becoming the new value against which the next pair is evaluated. If the json_doc is not a valid JSON document, or if any of the paths are not valid, or contain a * or ** wildcard, an error is returned. Examples -------- SET @json = '[1, 2, [3, 4]]'; SELECT JSON_ARRAY_APPEND(@json, '$[0]', 5) +-------------------------------------+ | JSON_ARRAY_APPEND(@json, '$[0]', 5) | +-------------------------------------+ | [[1, 5], 2, [3, 4]] | +-------------------------------------+ SELECT JSON_ARRAY_APPEND(@json, '$[1]', 6); +-------------------------------------+ | JSON_ARRAY_APPEND(@json, '$[1]', 6) | +-------------------------------------+ | [1, [2, 6], [3, 4]] | +-------------------------------------+ SELECT JSON_ARRAY_APPEND(@json, '$[1]', 6, '$[2]', 7); +------------------------------------------------+ | JSON_ARRAY_APPEND(@json, '$[1]', 6, '$[2]', 7) | +------------------------------------------------+ | [1, [2, 6], [3, 4, 7]] | +------------------------------------------------+ SELECT JSON_ARRAY_APPEND(@json, '$', 5); +----------------------------------+ | JSON_ARRAY_APPEND(@json, '$', 5) | +----------------------------------+ | [1, 2, [3, 4], 5] | +----------------------------------+ SET @json = '{"A": 1, "B": [2], "C": [3, 4]}'; SELECT JSON_ARRAY_APPEND(@json, '$.B', 5); +------------------------------------+ | JSON_ARRAY_APPEND(@json, '$.B', 5) | +------------------------------------+ | {"A": 1, "B": [2, 5], "C": [3, 4]} | +------------------------------------+ URL: https://mariadb.com/kb/en/json_array_append/https://mariadb.com/kb/en/json_array_append/  F  ,)JSON_ARRAY_INSERTJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_ARRAY_INSERT(json_doc, path, value[, path, value] ...) Description ----------- Inserts a value into a JSON document, returning the modified document, or NULL if any of the arguments are NULL. Evaluation is performed from left to right, with the resulting document from the previous pair becoming the new value against which the next pair is evaluated. If the json_doc is not a valid JSON document, or if any of the paths are not valid, or contain a * or ** wildcard, an error is returned. Examples -------- SET @json = '[1, 2, [3, 4]]'; SELECT JSON_ARRAY_INSERT(@json, '$[0]', 5); +-------------------------------------+ | JSON_ARRAY_INSERT(@json, '$[0]', 5) | +-------------------------------------+ | [5, 1, 2, [3, 4]] | +-------------------------------------+ SELECT JSON_ARRAY_INSERT(@json, '$[1]', 6); +-------------------------------------+ | JSON_ARRAY_INSERT(@json, '$[1]', 6) | +-------------------------------------+ | [1, 6, 2, [3, 4]] | +-------------------------------------+ SELECT JSON_ARRAY_INSERT(@json, '$[1]', 6, '$[2]', 7); +------------------------------------------------+ | JSON_ARRAY_INSERT(@json, '$[1]', 6, '$[2]', 7) | +------------------------------------------------+ | [1, 6, 7, 2, [3, 4]] | +------------------------------------------------+ URL: https://mariadb.com/kb/en/json_array_insert/https://mariadb.com/kb/en/json_array_insert/ ()JSON_CONTAINSJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_CONTAINS(json_doc, val[, path]) Description ----------- Returns whether or not the specified value is found in the given JSON document or, optionally, at the specified path within the document. Returns 1 if it does, 0 if not and NULL if any of the arguments are null. An error occurs if the document or path is not valid, or contains the * or ** wildcards. Examples -------- SET @json = '{"A": 0, "B": {"C": 1}, "D": 2}'; SELECT JSON_CONTAINS(@json, '2', '$.A'); +----------------------------------+ | JSON_CONTAINS(@json, '2', '$.A') | +----------------------------------+ | 0 | +----------------------------------+ SELECT JSON_CONTAINS(@json, '2', '$.D'); +----------------------------------+ | JSON_CONTAINS(@json, '2', '$.D') | +----------------------------------+ | 1 | +----------------------------------+ SELECT JSON_CONTAINS(@json, '{"C": 1}', '$.A'); +-----------------------------------------+ | JSON_CONTAINS(@json, '{"C": 1}', '$.A') | +-----------------------------------------+ | 0 | +-----------------------------------------+ SELECT JSON_CONTAINS(@json, '{"C": 1}', '$.B'); +-----------------------------------------+ | JSON_CONTAINS(@json, '{"C": 1}', '$.B') | +-----------------------------------------+ | 1 | +-----------------------------------------+ URL: https://mariadb.com/kb/en/json_contains/https://mariadb.com/kb/en/json_contains/-)JSON_CONTAINS_PATHJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_CONTAINS_PATH(json_doc, return_arg, path[, path] ...) Description ----------- Indicates whether the given JSON document contains data at the specified path or paths. Returns 1 if it does, 0 if not and NULL if any of the arguments are null. The return_arg can be one or all: one - Returns 1 if at least one path exists within the JSON document. all - Returns 1 only if all paths exist within the JSON document. Examples -------- SET @json = '{"A": 1, "B": [2], "C": [3, 4]}'; SELECT JSON_CONTAINS_PATH(@json, 'one', '$.A', '$.D'); +------------------------------------------------+ | JSON_CONTAINS_PATH(@json, 'one', '$.A', '$.D') | +------------------------------------------------+ | 1 | +------------------------------------------------+ 1 row in set (0.00 sec) SELECT JSON_CONTAINS_PATH(@json, 'all', '$.A', '$.D'); +------------------------------------------------+ | JSON_CONTAINS_PATH(@json, 'all', '$.A', '$.D') | +------------------------------------------------+ | 0 | +------------------------------------------------+ URL: https://mariadb.com/kb/en/json_contains_path/https://mariadb.com/kb/en/json_contains_path/ %)JSON_DEPTHJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_DEPTH(json_doc) Description ----------- Returns the maximum depth of the given JSON document, or NULL if the argument is null. An error will occur if the argument is an invalid JSON document. Scalar values or empty arrays or objects have a depth of 1. Arrays or objects that are not empty but contain only elements or member values of depth 1 will have a depth of 2. In other cases, the depth will be greater than 2. Examples -------- SELECT JSON_DEPTH('[]'), JSON_DEPTH('true'), JSON_DEPTH('{}'); +------------------+--------------------+------------------+ | JSON_DEPTH('[]') | JSON_DEPTH('true') | JSON_DEPTH('{}') | +------------------+--------------------+------------------+ | 1 | 1 | 1 | +------------------+--------------------+------------------+ SELECT JSON_DEPTH('[1, 2, 3]'), JSON_DEPTH('[[], {}, []]'); +-------------------------+----------------------------+ | JSON_DEPTH('[1, 2, 3]') | JSON_DEPTH('[[], {}, []]') | +-------------------------+----------------------------+ | 2 | 2 | +-------------------------+----------------------------+ SELECT JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]'); +---------------------------------------+ | JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]') | +---------------------------------------+ | 3 | +---------------------------------------+ URL: https://mariadb.com/kb/en/json_depth/https://mariadb.com/kb/en/json_depth/  [_  p&)JSON_EXISTSJSON functions were added in MariaDB 10.2.3. Syntax ------ Description ----------- Determines whether a specified JSON value exists in the given data. Returns 1 if found, 0 if not, or NULL if any of the inputs were NULL. Examples -------- SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2"); +------------------------------------------------------------+ | JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2") | +------------------------------------------------------------+ | 1 | +------------------------------------------------------------+ SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key3"); +------------------------------------------------------------+ | JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key3") | +------------------------------------------------------------+ | 0 | +------------------------------------------------------------+ SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[1]"); +---------------------------------------------------------------+ | JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[1]") | +---------------------------------------------------------------+ | 1 | +---------------------------------------------------------------+ SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[10]"); +----------------------------------------------------------------+ | JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[10]") | +----------------------------------------------------------------+ | 0 | +----------------------------------------------------------------+ URL: https://mariadb.com/kb/en/json_exists/https://mariadb.com/kb/en/json_exists/ ')JSON_EXTRACTJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_EXTRACT(json_doc, path[, path] ...) Description ----------- Extracts data from a JSON document. The extracted data is selected from the parts matching the path arguments. Returns all matched values; either as a single matched value, or, if the arguments could return multiple values, a result autowrapped as an array in the matching order. Returns NULL if no paths match or if any of the arguments are NULL. An error will occur if any path argument is not a valid path, or if the json_doc argument is not a valid JSON document. Examples -------- SET @json = '[1, 2, [3, 4]]'; SELECT JSON_EXTRACT(@json, '$[1]'); +-----------------------------+ | JSON_EXTRACT(@json, '$[1]') | +-----------------------------+ | 2 | +-----------------------------+ SELECT JSON_EXTRACT(@json, '$[2]'); +-----------------------------+ | JSON_EXTRACT(@json, '$[2]') | +-----------------------------+ | [3, 4] | +-----------------------------+ SELECT JSON_EXTRACT(@json, '$[2][1]'); +--------------------------------+ | JSON_EXTRACT(@json, '$[2][1]') | +--------------------------------+ | 4 | +--------------------------------+ URL: https://mariadb.com/kb/en/json_extract/https://mariadb.com/kb/en/json_extract/ L&)JSON_INSERTJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_INSERT(json_doc, path, val[, path, val] ...) Description ----------- Inserts data into a JSON document, returning the resulting document or NULL if any argument is null. An error will occur if the JSON document is not invalid, or if any of the paths are invalid or contain a * or ** wildcard. JSON_INSERT can only insert data while JSON_REPLACE can only update. JSON_SET can update or insert data. Examples -------- SET @json = '{ "A": 0, "B": [1, 2]}'; SELECT JSON_INSERT(@json, '$.C', '[3, 4]'); +--------------------------------------+ | JSON_INSERT(@json, '$.C', '[3, 4]') | +--------------------------------------+ | { "A": 0, "B": [1, 2], "C":"[3, 4]"} | +--------------------------------------+ URL: https://mariadb.com/kb/en/json_insert/https://mariadb.com/kb/en/json_insert/ $)JSON_KEYSJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_KEYS(json_doc[, path]) Description ----------- Returns the keys as a JSON array from the top-level value of a JSON object or, if the optional path argument is provided, the top-level keys from the path. Excludes keys from nested sub-objects in the top level value. The resulting array will be empty if the selected object is empty. Returns NULL if any of the arguments are null, a given path does not locate an object, or if the json_doc argument is not an object. An error will occur if JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard. Examples -------- SELECT JSON_KEYS('{"A": 1, "B": {"C": 2}}'); +--------------------------------------+ | JSON_KEYS('{"A": 1, "B": {"C": 2}}') | +--------------------------------------+ | ["A", "B"] | +--------------------------------------+ SELECT JSON_KEYS('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C'); +-----------------------------------------------------+ | JSON_KEYS('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C') | +-----------------------------------------------------+ | ["D"] | +-----------------------------------------------------+ URL: https://mariadb.com/kb/en/json_keys/https://mariadb.com/kb/en/json_keys/k" % ]  6&)JSON_LENGTHJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_LENGTH(json_doc[, path]) Description ----------- Returns the length of a JSON document, or, if the optional path argument is given, the length of the value within the document specified by the path. Returns NULL if any of the arguments argument are null or the path argument does not identify a value in the document. An error will occur if the JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard. Length will be determined as follow: A scalar's length is always 1. If an array, the number of elements in the array. If an object, the number of members in the object. The length of nested arrays or objects are not counted. Examples -------- URL: https://mariadb.com/kb/en/json_length/https://mariadb.com/kb/en/json_length/ %)JSON_MERGEJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_MERGE(json_doc, json_doc[, json_doc] ...) Description ----------- Merges the given JSON documents. Returns the merged result,or NULL if any argument is NULL. An error occurs if any of the arguments are not valid JSON documents. JSON_MERGE has been deprecated since MariaDB 10.2.25, MariaDB 10.3.16 and MariaDB 10.4.5. JSON_MERGE_PATCH is an RFC 7396-compliant replacement, and JSON_MERGE_PRESERVE is a synonym. Example SET @json1 = '[1, 2]'; SET @json2 = '[3, 4]'; SELECT JSON_MERGE(@json1,@json2); +---------------------------+ | JSON_MERGE(@json1,@json2) | +---------------------------+ | [1, 2, 3, 4] | +---------------------------+ URL: https://mariadb.com/kb/en/json_merge/https://mariadb.com/kb/en/json_merge/+)JSON_MERGE_PATCHJSON_MERGE_PATCH was introduced in MariaDB 10.2.25, MariaDB 10.3.16 and MariaDB 10.4.5. Syntax ------ JSON_MERGE_PATCH(json_doc, json_doc[, json_doc] ...) Description ----------- Merges the given JSON documents, returning the merged result, or NULL if any argument is NULL. JSON_MERGE_PATCH is an RFC 7396-compliant replacement for JSON_MERGE, which has been deprecated. Example SET @json1 = '[1, 2]'; SET @json2 = '[2, 3]'; SELECT JSON_MERGE_PATCH(@json1,@json2),JSON_MERGE_PRESERVE(@json1,@json2); +---------------------------------+------------------------------------+ | JSON_MERGE_PATCH(@json1,@json2) | JSON_MERGE_PRESERVE(@json1,@json2) | +---------------------------------+------------------------------------+ | [2, 3] | [1, 2, 2, 3] | +---------------------------------+------------------------------------+ URL: https://mariadb.com/kb/en/json_merge_patch/https://mariadb.com/kb/en/json_merge_patch/.)JSON_MERGE_PRESERVEJSON_MERGE_PRESERVE was introduced in MariaDB 10.2.25, MariaDB 10.3.16 and MariaDB 10.4.5. Syntax ------ JSON_MERGE_PRESERVE(json_doc, json_doc[, json_doc] ...) Description ----------- Merges the given JSON documents, returning the merged result, or NULL if any argument is NULL. JSON_MERGE_PRESERVE was introduced in MariaDB 10.2.25, MariaDB 10.3.16 and MariaDB 10.4.5 as a synonym for JSON_MERGE, which has been deprecated. Example SET @json1 = '[1, 2]'; SET @json2 = '[2, 3]'; SELECT JSON_MERGE_PATCH(@json1,@json2),JSON_MERGE_PRESERVE(@json1,@json2); +---------------------------------+------------------------------------+ | JSON_MERGE_PATCH(@json1,@json2) | JSON_MERGE_PRESERVE(@json1,@json2) | +---------------------------------+------------------------------------+ | [2, 3] | [1, 2, 2, 3] | +---------------------------------+------------------------------------+ URL: https://mariadb.com/kb/en/json_merge_preserve/https://mariadb.com/kb/en/json_merge_preserve/ %)JSON_QUERYJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_QUERY(json_doc, path) Description ----------- Given a JSON document, returns an object or array specified by the path. Returns NULL if not given a valid JSON document, or if there is no match. Examples -------- select json_query('{"key1":{"a":1, "b":[1,2]}}', '$.key1'); +-----------------------------------------------------+ | json_query('{"key1":{"a":1, "b":[1,2]}}', '$.key1') | +-----------------------------------------------------+ | {"a":1, "b":[1,2]} | +-----------------------------------------------------+ select json_query('{"key1":123, "key1": [1,2,3]}', '$.key1'); +-------------------------------------------------------+ | json_query('{"key1":123, "key1": [1,2,3]}', '$.key1') | +-------------------------------------------------------+ | [1,2,3] | +-------------------------------------------------------+ URL: https://mariadb.com/kb/en/json_query/https://mariadb.com/kb/en/json_query/ %)JSON_QUOTEJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_QUOTE(json_value) Description ----------- Quotes a string as a JSON value, usually for producing valid JSON string literals for inclusion in JSON documents. Wraps the string with double quote characters and escapes interior quotes and other special characters, returning a utf8mb4 string. Returns NULL if the argument is NULL. Examples -------- SELECT JSON_QUOTE('A'), JSON_QUOTE("B"), JSON_QUOTE('"C"'); +-----------------+-----------------+-------------------+ | JSON_QUOTE('A') | JSON_QUOTE("B") | JSON_QUOTE('"C"') | +-----------------+-----------------+-------------------+ | "A" | "B" | "\"C\"" | +-----------------+-----------------+-------------------+ URL: https://mariadb.com/kb/en/json_quote/https://mariadb.com/kb/en/json_quote/Z ; u.  &)JSON_REMOVEJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_REMOVE(json_doc, path[, path] ...) Description ----------- Removes data from a JSON document returning the result, or NULL if any of the arguments are null. If the element does not exist in the document, no changes are made. An error will occur if JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard. Path arguments are evaluated from left to right, with the result from the earlier evaluation being used as the value for the next. Examples -------- SELECT JSON_REMOVE('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C'); +-------------------------------------------------------+ | JSON_REMOVE('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C') | +-------------------------------------------------------+ | {"A": 1, "B": 2} | +-------------------------------------------------------+ SELECT JSON_REMOVE('["A", "B", ["C", "D"], "E"]', '$[1]'); +----------------------------------------------------+ | JSON_REMOVE('["A", "B", ["C", "D"], "E"]', '$[1]') | +----------------------------------------------------+ | ["A", ["C", "D"], "E"] | +----------------------------------------------------+ URL: https://mariadb.com/kb/en/json_remove/https://mariadb.com/kb/en/json_remove/ ')JSON_REPLACEJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_REPLACE(json_doc, path, val[, path, val] ...) Description ----------- Replaces existing values in a JSON document, returning the result, or NULL if any of the arguments are NULL. An error will occur if the JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard. Paths and values are evaluated from left to right, with the result from the earlier evaluation being used as the value for the next. JSON_REPLACE can only update data, while JSON_INSERT can only insert. JSON_SET can update or insert data. Examples -------- SELECT JSON_REPLACE('{ "A": 1, "B": [2, 3]}', '$.B[1]', 4); +-----------------------------------------------------+ | JSON_REPLACE('{ "A": 1, "B": [2, 3]}', '$.B[1]', 4) | +-----------------------------------------------------+ | { "A": 1, "B": [2, 4]} | +-----------------------------------------------------+ URL: https://mariadb.com/kb/en/json_replace/https://mariadb.com/kb/en/json_replace/ &)JSON_SEARCHJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_SEARCH(json_doc, return_arg, search_str[, escape_char[, path] ...]) Description ----------- Returns the path to the given string within a JSON document, or NULL if any of json_doc, search_str or a path argument is NULL; if the search string is not found, or if no path exists within the document. A warning will occur if the JSON document is not valid, any of the path arguments are not valid, if return_arg is neither one nor all, or if the escape character is not a constant. NULL will be returned. return_arg can be one of two values: 'one: Terminates after finding the first match, so will return one path string. If there is more than one match, it is undefined which is considered first. all: Returns all matching path strings, without duplicates. Multiple strings are autowrapped as an array. The order is undefined. Examples -------- SET @json = '["A", [{"B": "1"}], {"C":"AB"}, {"D":"BC"}]'; SELECT JSON_SEARCH(@json, 'one', 'AB'); +---------------------------------+ | JSON_SEARCH(@json, 'one', 'AB') | +---------------------------------+ | "$[2].C" | +---------------------------------+ URL: https://mariadb.com/kb/en/json_search/https://mariadb.com/kb/en/json_search/ $)JSON_TYPEJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_TYPE(json_val) Description ----------- Returns the type of a JSON value, or NULL if the argument is null. An error will occur if the argument is an invalid JSON value. The following is a complete list of the possible return types: Return type | Value | ARRAY | JSON array | BIT | MariaDB BIT scalar | BLOB | MariaDB binary types (BINARY, VARBINARY or BLOB) | BOOLEAN | JSON true/false literals | DATE | MariaDB DATE scalar | DATETIME | MariaDB DATETIME or TIMESTAMP scalar | DECIMAL | MariaDB DECIMAL or NUMERIC scalar | DOUBLE | MariaDB DOUBLE FLOAT scalar | INTEGER | MariaDB integer types (TINYINT, SMALLINT, MEDIUMINT, INT or BIGINT) | NULL | JSON null literal or NULL argument | OBJECT | JSON object | OPAQUE | Any valid JSON value that is not one of the other types. | STRING | MariaDB character types (CHAR, VARCHAR, TEXT, ENUM or SET) | TIME | MariaDB TIME scalar | Examples -------- SELECT JSON_TYPE('{"A": 1, "B": 2, "C": 3}'); +---------------------------------------+ | JSON_TYPE('{"A": 1, "B": 2, "C": 3}') | +---------------------------------------+ | OBJECT | +---------------------------------------+ URL: https://mariadb.com/kb/en/json_type/https://mariadb.com/kb/en/json_type/qM[ +0 |ǵ  ')JSON_UNQUOTEJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_UNQUOTE(val) Description ----------- Unquotes a JSON value, returning a string, or NULL if the argument is null. An error will occur if the given value begins and ends with double quotes and is an invalid JSON string literal. Certain character sequences have special meanings within a string. Usually, a backspace is ignored, but the escape sequences in the table below are recognised by MariaDB, unless the SQL Mode is set to NO_BACKSLASH_ESCAPES SQL. Escape sequence | Character | \" | Double quote (") | \b | Backspace | \f | Formfeed | \n | Newline (linefeed) | \r | Carriage return | \t | Tab | \\ | Backslash (\) | \uXXXX | UTF-8 bytes for Unicode value XXXX | Examples -------- SELECT JSON_UNQUOTE('"Monty"'); +-------------------------+ | JSON_UNQUOTE('"Monty"') | +-------------------------+ | Monty | +-------------------------+ With the default SQL Mode: SELECT JSON_UNQUOTE('Si\bng\ting'); +-----------------------------+ | JSON_UNQUOTE('Si\bng\ting') | +-----------------------------+ | Sng ing | +-----------------------------+ Setting NO_BACKSLASH_ESCAPES: SET @@sql_mode = 'NO_BACKSLASH_ESCAPES'; SELECT JSON_UNQUOTE('Si\bng\ting'); +-----------------------------+ | JSON_UNQUOTE('Si\bng\ting') | +-----------------------------+ | Si\bng\ting | +-----------------------------+ URL: https://mariadb.com/kb/en/json_unquote/https://mariadb.com/kb/en/json_unquote/ %)JSON_VALIDJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_VALID(value) Description ----------- Indicates whether the given value is a valid JSON document or not. Returns 1 if valid, 0 if not, and NULL if the argument is NULL. From MariaDB 10.4.3, the JSON_VALID function is automatically used as a CHECK constraint for the JSON data type alias in order to ensure that a valid json document is inserted. Examples -------- SELECT JSON_VALID('{"id": 1, "name": "Monty"}'); +------------------------------------------+ | JSON_VALID('{"id": 1, "name": "Monty"}') | +------------------------------------------+ | 1 | +------------------------------------------+ SELECT JSON_VALID('{"id": 1, "name": "Monty", "oddfield"}'); +------------------------------------------------------+ | JSON_VALID('{"id": 1, "name": "Monty", "oddfield"}') | +------------------------------------------------------+ | 0 | +------------------------------------------------------+ URL: https://mariadb.com/kb/en/json_valid/https://mariadb.com/kb/en/json_valid/ Y%)JSON_VALUEJSON functions were added in MariaDB 10.2.3. Syntax ------ JSON_VALUE(json_doc, path) Description ----------- Given a JSON document, returns the scalar specified by the path. Returns NULL if not given a valid JSON document, or if there is no match. Examples -------- select json_value('{"key1":123}', '$.key1'); +--------------------------------------+ | json_value('{"key1":123}', '$.key1') | +--------------------------------------+ | 123 | +--------------------------------------+ select json_value('{"key1": [1,2,3], "key1":123}', '$.key1'); +-------------------------------------------------------+ | json_value('{"key1": [1,2,3], "key1":123}', '$.key1') | +-------------------------------------------------------+ | 123 | +-------------------------------------------------------+ URL: https://mariadb.com/kb/en/json_value/https://mariadb.com/kb/en/json_value/ %*DENSE_RANKThe DENSE_RANK() function was first introduced with window functions in MariaDB 10.2.0. Syntax ------ DENSE_RANK() OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- DENSE_RANK() is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving the same result. Unlike the RANK() function, there are no skipped values if the preceding results are identical. It is also similar to the ROW_NUMBER() function except that in that function, identical values will receive a different row number for each result. Examples -------- The distinction between DENSE_RANK(), RANK() and ROW_NUMBER(): CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10)); INSERT INTO student VALUES ('Maths', 60, 'Thulile'), ('Maths', 60, 'Pritha'), ('Maths', 70, 'Voitto'), ('Maths', 55, 'Chun'), ('Biology', 60, 'Bilal'), ('Biology', 70, 'Roger'); SELECT RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank, DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank, ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num, course, mark, name FROM student ORDER BY course, mark DESC; +------+------------+---------+---------+------+---------+ | rank | dense_rank | row_num | course | mark | name | +------+------------+---------+---------+------+---------+ | 1 | 1 | 1 | Biology | 70 | Roger | | 2 | 2 | 2 | Biology | 60 | Bilal | | 1 | 1 | 1 | Maths | 70 | Voitto | | 2 | 2 | 2 | Maths | 60 | Thulile | | 2 | 2 | 3 | Maths | 60 | Pritha | | 4 | 3 | 4 | Maths | 55 | Chun | +------+------------+---------+---------+------+---------+ URL: https://mariadb.com/kb/en/dense_rank/https://mariadb.com/kb/en/dense_rank/ 9O  D WV}<*Window Functions OverviewWindow functions were introduced in MariaDB 10.2. Introduction Window functions allow calculations to be performed across a set of rows related to the current row. Syntax ------ function (expression) OVER ( [ PARTITION BY expression_list ] [ ORDER BY order_list [ frame_clause ] ] ) function: A valid window function expression_list: expression | column_name [, expr_list ] order_list: expression | column_name [ ASC | DESC ] [, ... ] frame_clause: {ROWS | RANGE} {frame_border | BETWEEN frame_border AND frame_border} frame_border: | UNBOUNDED PRECEDING | UNBOUNDED FOLLOWING | CURRENT ROW | expr PRECEDING | expr FOLLOWING Description ----------- In some ways, window functions are similar to aggregate functions in that they perform calculations across a set of rows. However, unlike aggregate functions, the output is not grouped into a single row. Non-aggregate window functions include CUME_DIST DENSE_RANK FIRST_VALUE LAG LAST_VALUE LEAD MEDIAN NTH_VALUE NTILE PERCENT_RANK PERCENTILE_CONT PERCENTILE_DISC RANK, ROW_NUMBER Aggregate functions that can also be used as window functions include AVG BIT_AND BIT_OR BIT_XOR COUNT MAX MIN STD STDDEV STDDEV_POP STDDEV_SAMP SUM VAR_POP VAR_SAMP VARIANCE Window function queries are characterised by the OVER keyword, following which the set of rows used for the calculation is specified. By default, the set of rows used for the calculation (the "window) is the entire dataset, which can be ordered with the ORDER BY clause. The PARTITION BY clause is used to reduce the window to a particular group within the dataset. For example, given the following data: CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); INSERT INTO student VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83); the following two queries return the average partitioned by test and by name respectively: SELECT name, test, score, AVG(score) OVER (PARTITION BY test) AS average_by_test FROM student; +---------+--------+-------+-----------------+ | name | test | score | average_by_test | +---------+--------+-------+-----------------+ | Chun | SQL | 75 | 65.2500 | | Chun | Tuning | 73 | 68.7500 | | Esben | SQL | 43 | 65.2500 | | Esben | Tuning | 31 | 68.7500 | | Kaolin | SQL | 56 | 65.2500 | | Kaolin | Tuning | 88 | 68.7500 | | Tatiana | SQL | 87 | 65.2500 | | Tatiana | Tuning | 83 | 68.7500 | +---------+--------+-------+-----------------+ SELECT name, test, score, AVG(score) OVER (PARTITION BY name) AS average_by_name FROM student; +---------+--------+-------+-----------------+ | name | test | score | average_by_name | +---------+--------+-------+-----------------+ | Chun | SQL | 75 | 74.0000 | | Chun | Tuning | 73 | 74.0000 | | Esben | SQL | 43 | 37.0000 | | Esben | Tuning | 31 | 37.0000 | | Kaolin | SQL | 56 | 72.0000 | | Kaolin | Tuning | 88 | 72.0000 | | Tatiana | SQL | 87 | 85.0000 | | Tatiana | Tuning | 83 | 85.0000 | +---------+--------+-------+-----------------+ It is also possible to specify which rows to include for the window function (for example, the current row and all preceding rows). See Window Frames for more details. Scope Window functions were introduced in SQL:2003, and their definition was expanded in subsequent versions of the standard. The last expansion was in the latest version of the standard, SQL:2011. Most database products support a subset of the standard, they implement some functions defined as late as in SQL:2011, and at the same time leave some parts of SQL:2008 unimplemented. MariaDB: Supports ROWS and RANGE-type frames All kinds of frame bounds are supported, including RANGE PRECEDING|FOLLOWING n frame bounds (unlike PostgreSQL or MS SQL Server) Does not yet support DATE[TIME] datatype and arithmetic for RANGE-type frames (MDEV-9727) Does not support GROUPS-type frames (it seems that no popular database supports it, either) Does not support frame exclusion (no other database seems to support it, either) (MDEV-9724) Does not support explicit NULLS FIRST or NULLS LAST. Does not support nested navigation in window functions (this is VALUE_OF(expr AT row_marker [, default_value) syntax) The following window functions are supported: "Streamable" window functions: ROW_NUMBER, RANK, DENSE_RANK, Window functions that can be streamed once the number of rows in partition is known: PERCENT_RANK, CUME_DIST, NTILE Aggregate functions that are currently supported as window functions are: COUNT, SUM, AVG, BIT_OR, BIT_AND, BIT_XOR. Aggregate functions with the DISTINCT specifier (e.g. COUNT( DISTINCT x)) are not supported as window functions. Links MDEV-6115 is the main jira task for window functions development. Other tasks are are attached as sub-tasks bb-10.2-mdev9543 is the feature tree for window functions. Development is ongoing, and this tree has the newest changes. Testcases are in mysql-test/t/win*.test Examples -------- Given the following sample data: CREATE TABLE users ( email VARCHAR(30), first_name VARCHAR(30), last_name VARCHAR(30), account_type VARCHAR(30) ); INSERT INTO users VALUES ('admin@boss.org', 'Admin', 'Boss', 'admin'), ('bob.carlsen@foo.bar', 'Bob', 'Carlsen', 'regular'), ('eddie.stevens@data.org', 'Eddie', 'Stevens', 'regular'), ('john.smith@xyz.org', 'John', 'Smith', 'regular'), ('root@boss.org', 'Root', 'Chief', 'admin') First, let's order the records by email alphabetically, giving each an ascending rnum value starting with 1. This will make use of the ROW_NUMBER window function: SELECT row_number() OVER (ORDER BY email) AS rnum, email, first_name, last_name, account_type FROM users ORDER BY email; +------+------------------------+------------+-----------+--------------+ | rnum | email | first_name | last_name | account_type | +------+------------------------+------------+-----------+--------------+ | 1 | admin@boss.org | Admin | Boss | admin | | 2 | bob.carlsen@foo.bar | Bob | Carlsen | regular | | 3 | eddie.stevens@data.org | Eddie | Stevens | regular | | 4 | john.smith@xyz.org | John | Smith | regular | | 5 | root@boss.org | Root | Chief | admin | +------+------------------------+------------+-----------+-------------- We can generate separate sequences based on account type, using the PARTITION BY clause: SELECT row_number() OVER (PARTITION BY account_type ORDER BY email) AS rnum, email, first_name, last_name, account_type FROM users ORDER BY account_type,email; +------+------------------------+------------+-----------+--------------+ | rnum | email | first_name | last_name | account_type | +------+------------------------+------------+-----------+--------------+ | 1 | admin@boss.org | Admin | Boss | admin | | 2 | root@boss.org | Root | Chief | admin | | 1 | bob.carlsen@foo.bar | Bob | Carlsen | regular | | 2 | eddie.stevens@data.org | Eddie | Stevens | regular | | 3 | john.smith@xyz.org | John | Smith | regular | +------+------------------------+------------+-----------+--------------+ Given the following structure and data, we want to find the top 5 salaries from each department. CREATE TABLE employee_salaries (dept VARCHAR(20), name VARCHAR(20), salary INT(11)); INSERT INTO employee_salaries VALUES ('Engineering', 'Dharma', 3500), ('Engineering', 'Bình', 3000), ('Engineering', 'Adalynn', 2800), ('Engineering', 'Samuel', 2500), ('Engineering', 'Cveta', 2200), ('Engineering', 'Ebele', 1800), ('Sales', 'Carbry', 500), ('Sales', 'Clytemnestra', 400), ('Sales', 'Juraj', 300), ('Sales', 'Kalpana', 300), ('Sales', 'Svantepolk', 250), ('Sales', 'Angelo', 200); We could do this without using window functions, as follows: select dept, name, salary from employee_salaries as t1 where (select count(t2.salary) from employee_salaries as t2 where t1.name != t2.name and t1.dept = t2.dept and t2.salary > t1.salary) URL: https://mariadb.com/kb/en/library/window-functions-overview/https://mariadb.com/kb/en/library/window-functions-overview/ tpJ  W0*Window FramesWindow functions were first introduced in MariaDB 10.2.0. Syntax ------ frame_clause: {ROWS | RANGE} {frame_border | BETWEEN frame_border AND frame_border} frame_border: | UNBOUNDED PRECEDING | UNBOUNDED FOLLOWING | CURRENT ROW | expr PRECEDING | expr FOLLOWING Description ----------- A basic overview of window functions is described in Window Functions Overview. Window frames expand this functionality by allowing the function to include a specified a number of rows around the current row. These include: All rows before the current row (UNBOUNDED PRECEDING), for example RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW All rows after the current row (UNBOUNDED FOLLOWING), for example RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING A set number of rows before the current row (expr PRECEDING) for example RANGE BETWEEN 6 PRECEDING AND CURRENT ROW A set number of rows after the current row (expr PRECEDING AND expr FOLLOWING) for example RANGE BETWEEN CURRENT ROW AND 2 FOLLOWING A specified number of rows both before and after the current row, for example RANGE BETWEEN 6 PRECEDING AND 3 FOLLOWING The following functions operate on window frames: AVG BIT_AND BIT_OR BIT_XOR COUNT LEAD MAX MIN NTILE STD STDDEV STDDEV_POP STDDEV_SAMP SUM VAR_POP VAR_SAMP VARIANCE Window frames are determined by the frame_clause in the window function request. Take the following example: CREATE TABLE `student_test` ( name char(10), test char(10), score tinyint(4) ); INSERT INTO student_test VALUES ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), ('Tatiana', 'SQL', 87); SELECT name, test, score, SUM(score) OVER () AS total_score FROM student_test; +---------+--------+-------+-------------+ | name | test | score | total_score | +---------+--------+-------+-------------+ | Chun | SQL | 75 | 453 | | Chun | Tuning | 73 | 453 | | Esben | SQL | 43 | 453 | | Esben | Tuning | 31 | 453 | | Kaolin | SQL | 56 | 453 | | Kaolin | Tuning | 88 | 453 | | Tatiana | SQL | 87 | 453 | +---------+--------+-------+-------------+ By not specifying an OVER condition, the SUM function is run over the entire dataset. However, if we specify an ORDER BY condition based on score (and order the entire result in the same way for clarity), the following result is returned: SELECT name, test, score, SUM(score) OVER (ORDER BY score) AS total_score FROM student_test ORDER BY score; +---------+--------+-------+-------------+ | name | test | score | total_score | +---------+--------+-------+-------------+ | Esben | Tuning | 31 | 31 | | Esben | SQL | 43 | 74 | | Kaolin | SQL | 56 | 130 | | Chun | Tuning | 73 | 203 | | Chun | SQL | 75 | 278 | | Tatiana | SQL | 87 | 365 | | Kaolin | Tuning | 88 | 453 | +---------+--------+-------+-------------+ The total_score column represents a running total of the current row, and all previous rows. The window frame in this example expands as the function proceeds. The above query makes use of the default to define the window frame. It could be written explicitly as follows: SELECT name, test, score, SUM(score) OVER (ORDER BY score RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS total_score FROM student_test ORDER BY score; +---------+--------+-------+-------------+ | name | test | score | total_score | +---------+--------+-------+-------------+ | Esben | Tuning | 31 | 31 | | Esben | SQL | 43 | 74 | | Kaolin | SQL | 56 | 130 | | Chun | Tuning | 73 | 203 | | Chun | SQL | 75 | 278 | | Tatiana | SQL | 87 | 365 | | Kaolin | Tuning | 88 | 453 | +---------+--------+-------+-------------+ Let's look at some alternatives: Firstly, applying the window function to the current row and all following rows can be done with the use of UNBOUNDED FOLLOWING: SELECT name, test, score, SUM(score) OVER (ORDER BY score RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS total_score FROM student_test ORDER BY score; +---------+--------+-------+-------------+ | name | test | score | total_score | +---------+--------+-------+-------------+ | Esben | Tuning | 31 | 453 | | Esben | SQL | 43 | 422 | | Kaolin | SQL | 56 | 379 | | Chun | Tuning | 73 | 323 | | Chun | SQL | 75 | 250 | | Tatiana | SQL | 87 | 175 | | Kaolin | Tuning | 88 | 88 | +---------+--------+-------+-------------+ It's possible to specify a number of rows, rather than the entire unbounded following or preceding set. The following example takes the current row, as well as the previous row: SELECT name, test, score, SUM(score) OVER (ORDER BY score ROWS BETWEEN 1 PRECEDING AND CURRENT ROW) AS total_score FROM student_test ORDER BY score; +---------+--------+-------+-------------+ | name | test | score | total_score | +---------+--------+-------+-------------+ | Esben | Tuning | 31 | 31 | | Esben | SQL | 43 | 74 | | Kaolin | SQL | 56 | 99 | | Chun | Tuning | 73 | 129 | | Chun | SQL | 75 | 148 | | Tatiana | SQL | 87 | 162 | | Kaolin | Tuning | 88 | 175 | +---------+--------+-------+-------------+ The current row and the following row: SELECT name, test, score, SUM(score) OVER (ORDER BY score ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS total_score FROM student_test ORDER BY score; +---------+--------+-------+-------------+ | name | test | score | total_score | +---------+--------+-------+-------------+ | Esben | Tuning | 31 | 74 | | Esben | SQL | 43 | 130 | | Kaolin | SQL | 56 | 172 | | Chun | Tuning | 73 | 204 | | Chun | SQL | 75 | 235 | | Tatiana | SQL | 87 | 250 | | Kaolin | Tuning | 88 | 175 | +---------+--------+-------+-------------+ URL: https://mariadb.com/kb/en/library/window-frames/https://mariadb.com/kb/en/library/window-frames/ Z4   &*FIRST_VALUEThe FIRST_VALUE() function was first introduced with other window functions in MariaDB 10.2. Syntax ------ FIRST_VALUE(expr) OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- FIRST_VALUE returns the first result from an ordered set, or NULL if no such result exists. Examples -------- CREATE TABLE t1 ( pk int primary key, a int, b int, c char(10), d decimal(10, 3), e real ); INSERT INTO t1 VALUES ( 1, 0, 1, 'one', 0.1, 0.001), ( 2, 0, 2, 'two', 0.2, 0.002), ( 3, 0, 3, 'three', 0.3, 0.003), ( 4, 1, 2, 'three', 0.4, 0.004), ( 5, 1, 1, 'two', 0.5, 0.005), ( 6, 1, 1, 'one', 0.6, 0.006), ( 7, 2, NULL, 'n_one', 0.5, 0.007), ( 8, 2, 1, 'n_two', NULL, 0.008), ( 9, 2, 2, NULL, 0.7, 0.009), (10, 2, 0, 'n_four', 0.8, 0.010), (11, 2, 10, NULL, 0.9, NULL); SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc, LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc, FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc, LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc FROM t1 ORDER BY pk DESC; +----+-----------+----------+------------+-----------+ | pk | first_asc | last_asc | first_desc | last_desc | +----+-----------+----------+------------+-----------+ | 11 | 1 | 11 | 11 | 11 | | 10 | 1 | 10 | 11 | 10 | | 9 | 1 | 9 | 11 | 9 | | 8 | 1 | 8 | 11 | 8 | | 7 | 1 | 7 | 11 | 7 | | 6 | 1 | 6 | 11 | 6 | | 5 | 1 | 5 | 11 | 5 | | 4 | 1 | 4 | 11 | 4 | | 3 | 1 | 3 | 11 | 3 | | 2 | 1 | 2 | 11 | 2 | | 1 | 1 | 1 | 11 | 1 | +----+-----------+----------+------------+-----------+ CREATE OR REPLACE TABLE t1 (i int); INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10); SELECT i, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS f_1f, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS l_1f, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p, FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f, LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f FROM t1; +------+------+------+--------+--------+--------+--------+--------+--------+ | i | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p | f_1f2f | f_1f2f | +------+------+------+--------+--------+--------+--------+--------+--------+ | 1 | 1 | 2 | 1 | 2 | NULL | NULL | 2 | 3 | | 2 | 2 | 3 | 1 | 3 | 1 | 1 | 3 | 4 | | 3 | 3 | 4 | 2 | 4 | 1 | 2 | 4 | 5 | | 4 | 4 | 5 | 3 | 5 | 2 | 3 | 5 | 6 | | 5 | 5 | 6 | 4 | 6 | 3 | 4 | 6 | 7 | | 6 | 6 | 7 | 5 | 7 | 4 | 5 | 7 | 8 | | 7 | 7 | 8 | 6 | 8 | 5 | 6 | 8 | 9 | | 8 | 8 | 9 | 7 | 9 | 6 | 7 | 9 | 10 | | 9 | 9 | 10 | 8 | 10 | 7 | 8 | 10 | 10 | | 10 | 10 | 10 | 9 | 10 | 8 | 9 | NULL | NULL | +------+------+------+--------+--------+--------+--------+--------+--------+ URL: https://mariadb.com/kb/en/first_value/https://mariadb.com/kb/en/first_value/)*LAGThe LAG() function was first introduced with other window functions in MariaDB 10.2. Syntax ------ LAG (expr[, offset]) OVER ( [ PARTITION BY partition_expression ] < ORDER BY order_list > ) Description ----------- The LAG function accesses data from a previous row according to the ORDER BY clause without the need for a self-join. The specific row is determined by the offset (default 1), which specifies the number of rows behind the current row to use. An offset of 0 is the current row. Examples -------- CREATE TABLE t1 (pk int primary key, a int, b int, c char(10), d decimal(10, 3), e real); INSERT INTO t1 VALUES ( 1, 0, 1, 'one', 0.1, 0.001), ( 2, 0, 2, 'two', 0.2, 0.002), ( 3, 0, 3, 'three', 0.3, 0.003), ( 4, 1, 2, 'three', 0.4, 0.004), ( 5, 1, 1, 'two', 0.5, 0.005), ( 6, 1, 1, 'one', 0.6, 0.006), ( 7, 2, NULL, 'n_one', 0.5, 0.007), ( 8, 2, 1, 'n_two', NULL, 0.008), ( 9, 2, 2, NULL, 0.7, 0.009), (10, 2, 0, 'n_four', 0.8, 0.010), (11, 2, 10, NULL, 0.9, NULL); SELECT pk, LAG(pk) OVER (ORDER BY pk) AS l, LAG(pk,1) OVER (ORDER BY pk) AS l1, LAG(pk,2) OVER (ORDER BY pk) AS l2, LAG(pk,0) OVER (ORDER BY pk) AS l0, LAG(pk,-1) OVER (ORDER BY pk) AS lm1, LAG(pk,-2) OVER (ORDER BY pk) AS lm2 FROM t1; +----+------+------+------+------+------+------+ | pk | l | l1 | l2 | l0 | lm1 | lm2 | +----+------+------+------+------+------+------+ | 1 | NULL | NULL | NULL | 1 | 2 | 3 | | 2 | 1 | 1 | NULL | 2 | 3 | 4 | | 3 | 2 | 2 | 1 | 3 | 4 | 5 | | 4 | 3 | 3 | 2 | 4 | 5 | 6 | | 5 | 4 | 4 | 3 | 5 | 6 | 7 | | 6 | 5 | 5 | 4 | 6 | 7 | 8 | | 7 | 6 | 6 | 5 | 7 | 8 | 9 | | 8 | 7 | 7 | 6 | 8 | 9 | 10 | | 9 | 8 | 8 | 7 | 9 | 10 | 11 | | 10 | 9 | 9 | 8 | 10 | 11 | NULL | | 11 | 10 | 10 | 9 | 11 | NULL | NULL | +----+------+------+------+------+------+------+ URL: https://mariadb.com/kb/en/lag/https://mariadb.com/kb/en/lag/h X \ RM^W !*LEADThe LEAD() function was first introduced with other window functions in MariaDB 10.2. Syntax ------ LEAD (expr[, offset]) OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- The LEAD function accesses data from a following row in the same result set without the need for a self-join. The specific row is determined by the offset (default 1), which specifies the number of rows ahead the current row to use. An offset of 0 is the current row. Example CREATE TABLE t1 (pk int primary key, a int, b int, c char(10), d decimal(10, 3), e real); INSERT INTO t1 VALUES ( 1, 0, 1, 'one', 0.1, 0.001), ( 2, 0, 2, 'two', 0.2, 0.002), ( 3, 0, 3, 'three', 0.3, 0.003), ( 4, 1, 2, 'three', 0.4, 0.004), ( 5, 1, 1, 'two', 0.5, 0.005), ( 6, 1, 1, 'one', 0.6, 0.006), ( 7, 2, NULL, 'n_one', 0.5, 0.007), ( 8, 2, 1, 'n_two', NULL, 0.008), ( 9, 2, 2, NULL, 0.7, 0.009), (10, 2, 0, 'n_four', 0.8, 0.010), (11, 2, 10, NULL, 0.9, NULL); SELECT pk, LEAD(pk) OVER (ORDER BY pk) AS l, LEAD(pk,1) OVER (ORDER BY pk) AS l1, LEAD(pk,2) OVER (ORDER BY pk) AS l2, LEAD(pk,0) OVER (ORDER BY pk) AS l0, LEAD(pk,-1) OVER (ORDER BY pk) AS lm1, LEAD(pk,-2) OVER (ORDER BY pk) AS lm2 FROM t1; +----+------+------+------+------+------+------+ | pk | l | l1 | l2 | l0 | lm1 | lm2 | +----+------+------+------+------+------+------+ | 1 | 2 | 2 | 3 | 1 | NULL | NULL | | 2 | 3 | 3 | 4 | 2 | 1 | NULL | | 3 | 4 | 4 | 5 | 3 | 2 | 1 | | 4 | 5 | 5 | 6 | 4 | 3 | 2 | | 5 | 6 | 6 | 7 | 5 | 4 | 3 | | 6 | 7 | 7 | 8 | 6 | 5 | 4 | | 7 | 8 | 8 | 9 | 7 | 6 | 5 | | 8 | 9 | 9 | 10 | 8 | 7 | 6 | | 9 | 10 | 10 | 11 | 9 | 8 | 7 | | 10 | 11 | 11 | NULL | 10 | 9 | 8 | | 11 | NULL | NULL | NULL | 11 | 10 | 9 | +----+------+------+------+------+------+------+ URL: https://mariadb.com/kb/en/lead/https://mariadb.com/kb/en/lead/!*Median Window FunctionThe MEDIAN() window function was first introduced with in MariaDB 10.3.3. Syntax ------ MEDIAN(median expression) OVER ( [ PARTITION BY partition_expression ] ) Description ----------- MEDIAN() is a window function that returns the median value of a range of values. It is a specific case of PERCENTILE_CONT, with an argument of 0.5 and the ORDER BY column the one in MEDIAN's argument. MEDIAN() OVER ( [ PARTITION BY partition_expression] ) Is equivalent to: PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY ) OVER ( [ PARTITION BY partition_expression ]) Examples -------- CREATE TABLE book_rating (name CHAR(30), star_rating TINYINT); INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 5); INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 3); INSERT INTO book_rating VALUES ('Lady of the Flies', 1); INSERT INTO book_rating VALUES ('Lady of the Flies', 2); INSERT INTO book_rating VALUES ('Lady of the Flies', 5); SELECT name, median(star_rating) OVER (PARTITION BY name) FROM book_rating; +-----------------------+----------------------------------------------+ | name | median(star_rating) OVER (PARTITION BY name) | +-----------------------+----------------------------------------------+ | Lord of the Ladybirds | 4.0000000000 | | Lord of the Ladybirds | 4.0000000000 | | Lady of the Flies | 2.0000000000 | | Lady of the Flies | 2.0000000000 | | Lady of the Flies | 2.0000000000 | +-----------------------+----------------------------------------------+ URL: https://mariadb.com/kb/en/median/https://mariadb.com/kb/en/median/ *NTILEThe NTILE() function was first introduced with window functions in MariaDB 10.2.0. Syntax ------ NTILE (expr) OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- NTILE() is a window function that returns an integer indicating which group a given row falls into. The number of groups is specified in the argument (expr), starting at one. Ordered rows in the partition are divided into the specified number of groups with as equal a size as possible. Examples -------- create table t1 ( pk int primary key, a int, b int ); insert into t1 values (11 , 0, 10), (12 , 0, 10), (13 , 1, 10), (14 , 1, 10), (18 , 2, 10), (15 , 2, 20), (16 , 2, 20), (17 , 2, 20), (19 , 4, 20), (20 , 4, 20); select pk, a, b, ntile(1) over (order by pk) from t1; +----+------+------+-----------------------------+ | pk | a | b | ntile(1) over (order by pk) | +----+------+------+-----------------------------+ | 11 | 0 | 10 | 1 | | 12 | 0 | 10 | 1 | | 13 | 1 | 10 | 1 | | 14 | 1 | 10 | 1 | | 15 | 2 | 20 | 1 | | 16 | 2 | 20 | 1 | | 17 | 2 | 20 | 1 | | 18 | 2 | 10 | 1 | | 19 | 4 | 20 | 1 | | 20 | 4 | 20 | 1 | +----+------+------+-----------------------------+ select pk, a, b, ntile(4) over (order by pk) from t1; +----+------+------+-----------------------------+ | pk | a | b | ntile(4) over (order by pk) | +----+------+------+-----------------------------+ | 11 | 0 | 10 | 1 | | 12 | 0 | 10 | 1 | | 13 | 1 | 10 | 1 | | 14 | 1 | 10 | 2 | | 15 | 2 | 20 | 2 | | 16 | 2 | 20 | 2 | | 17 | 2 | 20 | 3 | | 18 | 2 | 10 | 3 | | 19 | 4 | 20 | 4 | | 20 | 4 | 20 | 4 | +----+------+------+-----------------------------+ URL: https://mariadb.com/kb/en/ntile/https://mariadb.com/kb/en/ntile/ ^I Rp  \ '*PERCENT_RANKThe PERCENT_RANK() function was first introduced with window functions in MariaDB 10.2.0. Syntax ------ PERCENT_RANK() OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- PERCENT_RANK() is a window function that returns the relative percent rank of a given row. The following formula is used to calculate the percent rank: (rank - 1) / (number of rows in the window or partition - 1) Examples -------- create table t1 ( pk int primary key, a int, b int ); insert into t1 values ( 1 , 0, 10), ( 2 , 0, 10), ( 3 , 1, 10), ( 4 , 1, 10), ( 8 , 2, 10), ( 5 , 2, 20), ( 6 , 2, 20), ( 7 , 2, 20), ( 9 , 4, 20), (10 , 4, 20); select pk, a, b, rank() over (order by a) as rank, percent_rank() over (order by a) as pct_rank, cume_dist() over (order by a) as cume_dist from t1; +----+------+------+------+--------------+--------------+ | pk | a | b | rank | pct_rank | cume_dist | +----+------+------+------+--------------+--------------+ | 1 | 0 | 10 | 1 | 0.0000000000 | 0.2000000000 | | 2 | 0 | 10 | 1 | 0.0000000000 | 0.2000000000 | | 3 | 1 | 10 | 3 | 0.2222222222 | 0.4000000000 | | 4 | 1 | 10 | 3 | 0.2222222222 | 0.4000000000 | | 5 | 2 | 20 | 5 | 0.4444444444 | 0.8000000000 | | 6 | 2 | 20 | 5 | 0.4444444444 | 0.8000000000 | | 7 | 2 | 20 | 5 | 0.4444444444 | 0.8000000000 | | 8 | 2 | 10 | 5 | 0.4444444444 | 0.8000000000 | | 9 | 4 | 20 | 9 | 0.8888888889 | 1.0000000000 | | 10 | 4 | 20 | 9 | 0.8888888889 | 1.0000000000 | +----+------+------+------+--------------+--------------+ select pk, a, b, percent_rank() over (order by pk) as pct_rank, cume_dist() over (order by pk) as cume_dist from t1 order by pk; +----+------+------+--------------+--------------+ | pk | a | b | pct_rank | cume_dist | +----+------+------+--------------+--------------+ | 1 | 0 | 10 | 0.0000000000 | 0.1000000000 | | 2 | 0 | 10 | 0.1111111111 | 0.2000000000 | | 3 | 1 | 10 | 0.2222222222 | 0.3000000000 | | 4 | 1 | 10 | 0.3333333333 | 0.4000000000 | | 5 | 2 | 20 | 0.4444444444 | 0.5000000000 | | 6 | 2 | 20 | 0.5555555556 | 0.6000000000 | | 7 | 2 | 20 | 0.6666666667 | 0.7000000000 | | 8 | 2 | 10 | 0.7777777778 | 0.8000000000 | | 9 | 4 | 20 | 0.8888888889 | 0.9000000000 | | 10 | 4 | 20 | 1.0000000000 | 1.0000000000 | +----+------+------+--------------+--------------+ select pk, a, b, percent_rank() over (partition by a order by a) as pct_rank, cume_dist() over (partition by a order by a) as cume_dist from t1; +----+------+------+--------------+--------------+ | pk | a | b | pct_rank | cume_dist | +----+------+------+--------------+--------------+ | 1 | 0 | 10 | 0.0000000000 | 1.0000000000 | | 2 | 0 | 10 | 0.0000000000 | 1.0000000000 | | 3 | 1 | 10 | 0.0000000000 | 1.0000000000 | | 4 | 1 | 10 | 0.0000000000 | 1.0000000000 | | 5 | 2 | 20 | 0.0000000000 | 1.0000000000 | | 6 | 2 | 20 | 0.0000000000 | 1.0000000000 | | 7 | 2 | 20 | 0.0000000000 | 1.0000000000 | | 8 | 2 | 10 | 0.0000000000 | 1.0000000000 | | 9 | 4 | 20 | 0.0000000000 | 1.0000000000 | | 10 | 4 | 20 | 0.0000000000 | 1.0000000000 | +----+------+------+--------------+--------------+ URL: https://mariadb.com/kb/en/percent_rank/https://mariadb.com/kb/en/percent_rank/ **PERCENTILE_DISCThe PERCENTILE_DISC() window function was first introduced with in MariaDB 10.3.3. Syntax ------ Description ----------- PERCENTILE_DISC() (standing for discrete percentile) is a window function which returns the first value in the set whose ordered position is the same or more than the specified fraction. Essentially, the following process is followed to find the value to return: Get the number of rows in the partition. Walk through the partition, in order, until finding the the first row with CUME_DIST() > function_argument. Examples -------- CREATE TABLE book_rating (name CHAR(30), star_rating TINYINT); INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 5); INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 3); INSERT INTO book_rating VALUES ('Lady of the Flies', 1); INSERT INTO book_rating VALUES ('Lady of the Flies', 2); INSERT INTO book_rating VALUES ('Lady of the Flies', 5); SELECT name, PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+------+ | name | pc | +-----------------------+------+ | Lord of the Ladybirds | 3 | | Lord of the Ladybirds | 3 | | Lady of the Flies | 2 | | Lady of the Flies | 2 | | Lady of the Flies | 2 | +-----------------------+------+ 5 rows in set (0.000 sec) SELECT name, PERCENTILE_DISC(0) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+------+ | name | pc | +-----------------------+------+ | Lord of the Ladybirds | 3 | | Lord of the Ladybirds | 3 | | Lady of the Flies | 1 | | Lady of the Flies | 1 | | Lady of the Flies | 1 | +-----------------------+------+ 5 rows in set (0.000 sec) SELECT name, PERCENTILE_DISC(1) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+------+ | name | pc | +-----------------------+------+ | Lord of the Ladybirds | 5 | | Lord of the Ladybirds | 5 | | Lady of the Flies | 5 | | Lady of the Flies | 5 | | Lady of the Flies | 5 | +-----------------------+------+ 5 rows in set (0.000 sec) SELECT name, PERCENTILE_DISC(0.6) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+------+ | name | pc | +-----------------------+------+ | Lord of the Ladybirds | 5 | | Lord of the Ladybirds | 5 | | Lady of the Flies | 2 | | Lady of the Flies | 2 | | Lady of the Flies | 2 | +-----------------------+------ URL: https://mariadb.com/kb/en/percentile_disc/https://mariadb.com/kb/en/percentile_disc/ 9 G  **PERCENTILE_CONTThe PERCENTILE_CONT() window function was first introduced with in MariaDB 10.3.3. Syntax ------ Description ----------- PERCENTILE_CONT() (standing for continuous percentile) is a window function which returns a value which corresponds to the given fraction in the sort order. If required, it will interpolate between adjacent input items. Essentially, the following process is followed to find the value to return: Get the number of rows in the partition, denoted by N RN = p*(N-1), where p denotes the argument to the PERCENTILE_CONT function calculate the FRN(floor row number) and CRN(column row number for the group( FRN= floor(RN) and CRN = ceil(RN)) look up rows FRN and CRN If (CRN = FRN = RN) then the result is (value of expression from row at RN) Otherwise the result is (CRN - RN) * (value of expression for row at FRN) + (RN - FRN) * (value of expression for row at CRN) The MEDIAN function is a specific case of PERCENTILE_CONT, equivalent to PERCENTILE_CONT(0.5). Examples -------- CREATE TABLE book_rating (name CHAR(30), star_rating TINYINT); INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 5); INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 3); INSERT INTO book_rating VALUES ('Lady of the Flies', 1); INSERT INTO book_rating VALUES ('Lady of the Flies', 2); INSERT INTO book_rating VALUES ('Lady of the Flies', 5); SELECT name, PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+--------------+ | name | pc | +-----------------------+--------------+ | Lord of the Ladybirds | 4.0000000000 | | Lord of the Ladybirds | 4.0000000000 | | Lady of the Flies | 2.0000000000 | | Lady of the Flies | 2.0000000000 | | Lady of the Flies | 2.0000000000 | +-----------------------+--------------+ SELECT name, PERCENTILE_CONT(1) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+--------------+ | name | pc | +-----------------------+--------------+ | Lord of the Ladybirds | 5.0000000000 | | Lord of the Ladybirds | 5.0000000000 | | Lady of the Flies | 5.0000000000 | | Lady of the Flies | 5.0000000000 | | Lady of the Flies | 5.0000000000 | +-----------------------+--------------+ SELECT name, PERCENTILE_CONT(0) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+--------------+ | name | pc | +-----------------------+--------------+ | Lord of the Ladybirds | 3.0000000000 | | Lord of the Ladybirds | 3.0000000000 | | Lady of the Flies | 1.0000000000 | | Lady of the Flies | 1.0000000000 | | Lady of the Flies | 1.0000000000 | +-----------------------+--------------+ SELECT name, PERCENTILE_CONT(0.6) WITHIN GROUP (ORDER BY star_rating) OVER (PARTITION BY name) AS pc FROM book_rating; +-----------------------+--------------+ | name | pc | +-----------------------+--------------+ | Lord of the Ladybirds | 4.2000000000 | | Lord of the Ladybirds | 4.2000000000 | | Lady of the Flies | 2.6000000000 | | Lady of the Flies | 2.6000000000 | | Lady of the Flies | 2.6000000000 | +-----------------------+--------------+ URL: https://mariadb.com/kb/en/percentile_cont/https://mariadb.com/kb/en/percentile_cont/*RANKThe RANK() function was first introduced with window functions in MariaDB 10.2.0. Syntax ------ RANK() OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- RANK() is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving the same result. It is similar to the ROW_NUMBER() function except that in that function, identical values will receive a different row number for each result. Examples -------- The distinction between DENSE_RANK(), RANK() and ROW_NUMBER(): CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10)); INSERT INTO student VALUES ('Maths', 60, 'Thulile'), ('Maths', 60, 'Pritha'), ('Maths', 70, 'Voitto'), ('Maths', 55, 'Chun'), ('Biology', 60, 'Bilal'), ('Biology', 70, 'Roger'); SELECT RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank, DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank, ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num, course, mark, name FROM student ORDER BY course, mark DESC; +------+------------+---------+---------+------+---------+ | rank | dense_rank | row_num | course | mark | name | +------+------------+---------+---------+------+---------+ | 1 | 1 | 1 | Biology | 70 | Roger | | 2 | 2 | 2 | Biology | 60 | Bilal | | 1 | 1 | 1 | Maths | 70 | Voitto | | 2 | 2 | 2 | Maths | 60 | Thulile | | 2 | 2 | 3 | Maths | 60 | Pritha | | 4 | 3 | 4 | Maths | 55 | Chun | +------+------------+---------+---------+------+---------+ URL: https://mariadb.com/kb/en/rank/https://mariadb.com/kb/en/rank/  #a %*ROW_NUMBERROW_NUMBER() was first introduced with window functions in MariaDB 10.2.0. Syntax ------ ROW_NUMBER() OVER ( [ PARTITION BY partition_expression ] [ ORDER BY order_list ] ) Description ----------- ROW_NUMBER() is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving different row numbers. It is similar to the RANK() and DENSE_RANK() functions except that in that function, identical values will receive the same rank for each result. Examples -------- The distinction between DENSE_RANK(), RANK() and ROW_NUMBER(): CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10)); INSERT INTO student VALUES ('Maths', 60, 'Thulile'), ('Maths', 60, 'Pritha'), ('Maths', 70, 'Voitto'), ('Maths', 55, 'Chun'), ('Biology', 60, 'Bilal'), ('Biology', 70, 'Roger'); SELECT RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank, DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank, ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num, course, mark, name FROM student ORDER BY course, mark DESC; +------+------------+---------+---------+------+---------+ | rank | dense_rank | row_num | course | mark | name | +------+------------+---------+---------+------+---------+ | 1 | 1 | 1 | Biology | 70 | Roger | | 2 | 2 | 2 | Biology | 60 | Bilal | | 1 | 1 | 1 | Maths | 70 | Voitto | | 2 | 2 | 2 | Maths | 60 | Thulile | | 2 | 2 | 3 | Maths | 60 | Pritha | | 4 | 3 | 4 | Maths | 55 | Chun | +------+------------+---------+---------+------+---------+ URL: https://mariadb.com/kb/en/row_number/https://mariadb.com/kb/en/row_number//+SPIDER_BG_DIRECT_SQLSyntax ------ SPIDER_BG_DIRECT_SQL('sql', 'tmp_table_list', 'parameters') Description ----------- Executes the given SQL statement in the background on the remote server, as defined in the parameters listing. If the query returns a result-set, it sttores the results in the given temporary table. When the given SQL statement executes successfully, this function returns the number of called UDF's. It returns 0 when the given SQL statement fails. This function is a UDF installed with the Spider storage engine. Examples -------- SELECT SPIDER_BG_DIRECT_SQL('SELECT * FROM example_table', '', 'srv "node1", port "8607"') AS "Direct Query"; +--------------+ | Direct Query | +--------------+ | 1 | +--------------+ Parameters error_rw_mode Description: Returns empty results on network error. 0 : Return error on getting network error. 1: Return 0 records on getting network error. Default Table Value: 0 DSN Parameter Name: erwm URL: https://mariadb.com/kb/en/spider_bg_direct_sql/https://mariadb.com/kb/en/spider_bg_direct_sql/*-+SPIDER_COPY_TABLESSyntax ------ SPIDER_COPY_TABLES(spider_table_name, source_link_id, destination_link_id_list [,parameters]) Description ----------- A UDF installed with the Spider Storage Engine, this function copies table data from source_link_id to destination_link_id_list. The service does not need to be stopped in order to copy. If the Spider table is partitioned, the name must be of the format table_name#P#partition_name. The partition name can be viewed in the mysql.spider_tables table, for example: SELECT table_name FROM mysql.spider_tables; +-------------+ | table_name | +-------------+ | spt_a#P#pt1 | | spt_a#P#pt2 | | spt_a#P#pt3 | +-------------+ Returns 1 if the data was copied successfully, or 0 if copying the data failed. URL: https://mariadb.com/kb/en/spider_copy_tables/https://mariadb.com/kb/en/spider_copy_tables/L,+SPIDER_DIRECT_SQLSyntax ------ SPIDER_DIRECT_SQL('sql', 'tmp_table_list', 'parameters') Description ----------- A UDF installed with the Spider Storage Engine, this function is used to execute the SQL string sql on the remote server, as defined in parameters. If any resultsets are returned, they are stored in the tmp_table_list. The function returns 1 if the SQL executes successfully, or 0 if it fails. Examples -------- SELECT SPIDER_DIRECT_SQL('SELECT * FROM s', '', 'srv "node1", port "8607"'); +----------------------------------------------------------------------+ | SPIDER_DIRECT_SQL('SELECT * FROM s', '', 'srv "node1", port "8607"') | +----------------------------------------------------------------------+ | 1 | +----------------------------------------------------------------------+ URL: https://mariadb.com/kb/en/spider_direct_sql/https://mariadb.com/kb/en/spider_direct_sql/ !%,COLUMN_ADDThe Dynamic columns feature was introduced in MariaDB 5.3. Syntax ------ COLUMN_ADD(dyncol_blob, column_nr, value [as type], [column_nr, value [as type]]...); COLUMN_ADD(dyncol_blob, column_name, value [as type], [column_name, value [as type]]...); Description ----------- Adds or updates dynamic columns. dyncol_blob must be either a valid dynamic columns blob (for example, COLUMN_CREATE returns such blob), or an empty string. column_name specifies the name of the column to be added. If dyncol_blob already has a column with this name, it will be overwritten. value specifies the new value for the column. Passing a NULL value will cause the column to be deleted. as type is optional. See #datatypes section for a discussion about types. The return value is a dynamic column blob after the modifications. Examples -------- -- MariaDB 5.3+: UPDATE tbl SET dyncol_blob=COLUMN_ADD(dyncol_blob, 1 /*column id*/, "value") WHERE id=1; -- MariaDB 10.0.1+: UPDATE t1 SET dyncol_blob=COLUMN_ADD(dyncol_blob, "column_name", "value") WHERE id=1; Note: COLUMN_ADD() is a regular function (just like CONCAT()), hence, in order to update the value in the table you have to use the UPDATE ... SET dynamic_col=COLUMN_ADD(dynamic_col, ....) pattern. URL: https://mariadb.com/kb/en/column_add/https://mariadb.com/kb/en/column_add/)^ w? O3a w(,COLUMN_CREATEThe Dynamic columns feature was introduced in MariaDB 5.3. Syntax ------ COLUMN_CREATE(column_nr, value [as type], [column_nr, value [as type]]...); COLUMN_CREATE(column_name, value [as type], [column_name, value [as type]]...); Description ----------- Returns a dynamic columns blob that stores the specified columns with values. The return value is suitable for storing in a table further modification with other dynamic columns functions The as type part allows one to specify the value type. In most cases, this is redundant because MariaDB will be able to deduce the type of the value. Explicit type specification may be needed when the type of the value is not apparent. For example, a literal '2012-12-01' has a CHAR type by default, one will need to specify '2012-12-01' AS DATE to have it stored as a date. See Dynamic Columns:Datatypes for further details. Examples -------- -- MariaDB 5.3+: INSERT INTO tbl SET dyncol_blob=COLUMN_CREATE(1 /*column id*/, "value"); -- MariaDB 10.0.1+: INSERT INTO tbl SET dyncol_blob=COLUMN_CREATE("column_name", "value"); URL: https://mariadb.com/kb/en/column_create/https://mariadb.com/kb/en/column_create/ %,COLUMN_GETThe Dynamic columns feature was introduced in MariaDB 5.3. Syntax ------ COLUMN_GET(dyncol_blob, column_nr as type); COLUMN_GET(dyncol_blob, column_name as type); Description ----------- Gets the value of a dynamic column by its name. If no column with the given name exists, NULL will be returned. column_name as type requires that one specify the datatype of the dynamic column they are reading. This may seem counter-intuitive: why would one need to specify which datatype they're retrieving? Can't the dynamic columns system figure the datatype from the data being stored? The answer is: SQL is a statically-typed language. The SQL interpreter needs to know the datatypes of all expressions before the query is run (for example, when one is using prepared statements and runs "select COLUMN_GET(...)", the prepared statement API requires the server to inform the client about the datatype of the column being read before the query is executed and the server can see what datatype the column actually has). A note about lengths If you're running queries like: SELECT COLUMN_GET(blob, 'colname' as CHAR) ... without specifying a maximum length (i.e. using #as CHAR#, not as CHAR(n)), MariaDB will report the maximum length of the resultset column to be 53,6870,911 for MariaDB 5.3-10.0.0 and 16,777,216 for MariaDB 10.0.1+. This may cause excessive memory usage in some client libraries, because they try to pre-allocate a buffer of maximum resultset width. To avoid this problem, use CHAR(n) whenever you're using COLUMN_GET in the select list. See Dynamic Columns:Datatypes for more information about datatypes. URL: https://mariadb.com/kb/en/column_get/https://mariadb.com/kb/en/column_get/ &,COLUMN_JSONCOLUMN_JSON was introduced in MariaDB 10.0.1 Syntax ------ COLUMN_JSON(dyncol_blob) Description ----------- Returns a JSON representation of data in dyncol_blob. Can also be used to display nested columns. See dynamic columns for more information. Example select item_name, COLUMN_JSON(dynamic_cols) from assets; +-----------------+----------------------------------------+ | item_name | COLUMN_JSON(dynamic_cols) | +-----------------+----------------------------------------+ | MariaDB T-shirt | {"size":"XL","color":"blue"} | | Thinkpad Laptop | {"color":"black","warranty":"3 years"} | +-----------------+----------------------------------------+ Limitation: COLUMN_JSON will decode nested dynamic columns at a nesting level of not more than 10 levels deep. Dynamic columns that are nested deeper than 10 levels will be shown as BINARY string, without encoding. URL: https://mariadb.com/kb/en/column_json/https://mariadb.com/kb/en/column_json/  L[@ 8.Instant ADD COLUMN for InnoDBInstant ALTER TABLE ... ADD COLUMN for InnoDB was introduced in MariaDB 10.3.2. The INSTANT option for the ALGORITHM clause was introduced in MariaDB 10.3.7. Normally, adding a column to a table requires the full table to be rebuilt. The complexity of the operation is proportional to the size of the table, or O(n·m) where n is the number of rows in the table and m is the number of indexes. In MariaDB 10.0 and later, the ALTER TABLE statement supports online DDL for storage engines that have implemented the relevant online DDL algorithms and locking strategies. The InnoDB storage engine has implemented online DDL for many operations. These online DDL optimizations allow concurrent DML to the table in many cases, even if the table needs to be rebuilt. See InnoDB Online DDL Overview for more information about online DDL with InnoDB. Allowing concurrent DML during the operation does not solve all problems. When a column was added to a table with the older in-place optimization, the resulting table rebuild could still significantly increase the I/O and memory consumption and cause replication lag. In contrast, with the new instant ALTER TABLE ... ADD COLUMN, all that is needed is an O(log n) operation to insert a special hidden record into the table, and an update of the data dictionary. For a large table, instead of taking several hours, the operation would be completed in the blink of an eye. The ALTER TABLE ... ADD COLUMN operation is only slightly more expensive than a regular INSERT, due to locking constraints. In the past, some developers may have implemented a kind of "instant add column" in the application by encoding multiple columns in a single TEXT or BLOB column. MariaDB Dynamic Columns was an early example of that. A more recent example is JSON and related string manipulation functions. Adding real columns has the following advantages over encoding columns into a single "expandable" column: Efficient storage in a native binary format Data type safety Indexes can be built natively Constraints are available: UNIQUE, CHECK, FOREIGN KEY DEFAULT values can be specified Triggers can be written more easily With instant ALTER TABLE ... ADD COLUMN, you can enjoy all the benefits of structured storage without the drawback of having to rebuild the table. Instant ALTER TABLE ... ADD COLUMN is available for both old and new InnoDB tables. Basically you can just upgrade from MySQL 5.x or MariaDB and start adding columns instantly. Columns instantly added to a table exist in a separate data structure from the main table definition, similar to how InnoDB separates BLOB columns. If the table ever becomes empty, (such as from TRUNCATE or DELETE statements), InnoDB incorporates the instantly added columns into the main table definition. See InnoDB Online DDL Operations with ALGORITHM=INSTANT: Non-canonical Storage Format Caused by Some Operations for more information. The operation is also crash safe. If the server is killed while executing an instant ALTER TABLE ... ADD COLUMN, when the table is restored InnoDB integrates the new column, flattening the table definition. Limitations In MariaDB 10.3, instant ALTER TABLE ... ADD COLUMN only applies when the added columns appear last in the table. The place specifier LAST is the default. If AFTER col is specified, then col must be the last column, or the operation will require the table to be rebuilt. In MariaDB 10.4, this restriction has been lifted. If the table contains a hidden FTS_DOC_ID column due to a FULLTEXT INDEX, then instant ALTER TABLE ... ADD COLUMN will not be possible. InnoDB data files after instant ALTER TABLE ... ADD COLUMN cannot be imported to older versions of MariaDB or MySQL without first being rebuilt. After using Instant ALTER TABLE ... ADD COLUMN, any table-rebuilding operation such as ALTER TABLE … FORCE will incorporate instantaneously added columns into the main table body. Instant ALTER TABLE ... ADD COLUMN is not available for ROW_FORMAT=COMPRESSED. In MariaDB 10.3, ALTER TABLE … DROP COLUMN requires the table to be rebuilt. In MariaDB 10.4, this restriction has been lifted. Example CREATE TABLE t(id INT PRIMARY KEY, u INT UNSIGNED NOT NULL UNIQUE) ENGINE=InnoDB; INSERT INTO t(id,u) VALUES(1,1),(2,2),(3,3); ALTER TABLE t ADD COLUMN (d DATETIME DEFAULT current_timestamp(), p POINT NOT NULL DEFAULT ST_GeomFromText('POINT(0 0)'), t TEXT CHARSET utf8 DEFAULT 'The quick brown fox jumps over the lazy dog'); UPDATE t SET t=NULL WHERE id=3; SELECT id,u,d,ST_AsText(p),t FROM t; SELECT variable_value FROM information_schema.global_status WHERE variable_name = 'innodb_instant_alter_column'; The above example illustrates that when the added columns are declared NOT NULL, a DEFAULT value must be available, either implied by the data type or set explicitly by the user. The expression need not be constant, but it must not refer to the columns of the table, such as DEFAULT u+1 (a MariaDB extension). The DEFAULT current_timestamp() would be evaluated at the time of the ALTER TABLE and apply to each row, like it does for non-instant ALTER TABLE. If a subsequent ALTER TABLE changes the DEFAULT value for subsequent INSERT, the values of the columns in existing records will naturally be unaffected. The design was brainstormed in April by engineers from MariaDB Corporation, Alibaba and Tencent. A prototype was developed by Vin Chen (陈福荣) from the Tencent Game DBA Team. URL: https://mariadb.com/kb/en/instant-add-column-for-innodb/https://mariadb.com/kb/en/instant-add-column-for-innodb/ !ʣ  s30Full-Text Index OverviewMariaDB has support for full-text indexing and searching: A full-text index in MariaDB is an index of type FULLTEXT, and it allows more options when searching for portions of text from a field. Full-text indexes can be used only with MyISAM and Aria tables, from MariaDB 10.0.5 with InnoDB tables and from MariaDB 10.0.15 with Mroonga tables, and can be created only for CHAR, VARCHAR, or TEXT columns. Partitioned tables cannot contain fulltext indexes, even if the storage engine supports them. A FULLTEXT index definition can be given in the CREATE TABLE statement when a table is created, or added later using ALTER TABLE or CREATE INDEX. For large data sets, it is much faster to load your data into a table that has no FULLTEXT index and then create the index after that, than to load data into a table that has an existing FULLTEXT index. Full-text searching is performed using MATCH() ... AGAINST syntax. MATCH() takes a comma-separated list that names the columns to be searched. AGAINST takes a string to search for, and an optional modifier that indicates what type of search to perform. The search string must be a literal string, not a variable or a column name. MATCH (col1,col2,...) AGAINST (expr [search_modifier]) Excluded Results Partial words are excluded. Words less than 4 characters in length (3 or less) will not be stored in the fulltext index. This value can be adjusted by changing the ft_min_word_length system variable (or, for InnoDB, innodb_ft_min_token_size). Words longer than 84 characters in length will also not be stored in the fulltext index. This values can be adjusted by changing the ft_max_word_length system variable (or, for InnoDB, innodb_ft_max_token_size). Stopwords are a list of common words such as "once" or "then" that do not reflect in the search results unless IN BOOLEAN MODE is used. The stopword list for MyISAM/Aria tables and InnoDB tables can differ. See stopwords for details and a full list, as well as for details on how to change the default list. For MyISAM/Aria fulltext indexes only, if a word appears in more than half the rows, it is also excluded from the results of a fulltext search. For InnoDB indexes, only committed rows appear - modifications from the current transaction do not apply. Relevance MariaDB calculates a relevance for each result, based on a number of factors, including the number of words in the index, the number of unique words in a row, the total number of words in both the index and the result, and the weight of the word. In English, 'cool' will be weighted less than 'dandy', at least at present! The relevance can be returned as part of a query simply by using the MATCH function in the field list. Types of Full-Text search IN NATURAL LANGUAGE MODE IN NATURAL LANGUAGE MODE is the default type of full-text search, and the keywords can be omitted. There are no special operators, and searches consist of one or more comma-separated keywords. Searches are returned in descending order of relevance. IN BOOLEAN MODE Boolean search permits the use of a number of special operators: Operator | Description | + | The word is mandatory in all rows returned. | - | The word cannot appear in any row returned. | < | The word that follows has a lower relevance than other words, although rows containing it will still match | > | The word that follows has a higher relevance than other words. | () | Used to group words into subexpressions. | ~ | The word following contributes negatively to the relevance of the row (which is different to the '-' operator, which specifically excludes the word, or the ' URL: https://mariadb.com/kb/en/full-text-index-overview/https://mariadb.com/kb/en/full-text-index-overview/ [