drop table if exists t1,t2,t3,t4; drop database if exists mysqltest; create table t1 (id int unsigned not null auto_increment, code tinyint unsigned not null, name char(20) not null, primary key (id), key (code), unique (name)) engine=innodb; insert into t1 (code, name) values (1, 'Tim'), (1, 'Monty'), (2, 'David'), (2, 'Erik'), (3, 'Sasha'), (3, 'Jeremy'), (4, 'Matt'); select id, code, name from t1 order by id; id code name 1 1 Tim 2 1 Monty 3 2 David 4 2 Erik 5 3 Sasha 6 3 Jeremy 7 4 Matt update ignore t1 set id = 8, name = 'Sinisa' where id < 3; select id, code, name from t1 order by id; id code name 2 1 Monty 3 2 David 4 2 Erik 5 3 Sasha 6 3 Jeremy 7 4 Matt 8 1 Sinisa update ignore t1 set id = id + 10, name = 'Ralph' where id < 4; select id, code, name from t1 order by id; id code name 3 2 David 4 2 Erik 5 3 Sasha 6 3 Jeremy 7 4 Matt 8 1 Sinisa 12 1 Ralph drop table t1; CREATE TABLE t1 ( id int(11) NOT NULL auto_increment, parent_id int(11) DEFAULT '0' NOT NULL, level tinyint(4) DEFAULT '0' NOT NULL, PRIMARY KEY (id), KEY parent_id (parent_id), KEY level (level) ) engine=innodb; INSERT INTO t1 VALUES (1,0,0),(3,1,1),(4,1,1),(8,2,2),(9,2,2),(17,3,2),(22,4,2),(24,4,2),(28,5,2),(29,5,2),(30,5,2),(31,6,2),(32,6,2),(33,6,2),(203,7,2),(202,7,2),(20,3,2),(157,0,0),(193,5,2),(40,7,2),(2,1,1),(15,2,2),(6,1,1),(34,6,2),(35,6,2),(16,3,2),(7,1,1),(36,7,2),(18,3,2),(26,5,2),(27,5,2),(183,4,2),(38,7,2),(25,5,2),(37,7,2),(21,4,2),(19,3,2),(5,1,1),(179,5,2); update t1 set parent_id=parent_id+100; select * from t1 where parent_id=102; id parent_id level 8 102 2 9 102 2 15 102 2 update t1 set id=id+1000; update t1 set id=1024 where id=1009; Got one of the listed errors select * from t1; id parent_id level 1001 100 0 1002 101 1 1003 101 1 1004 101 1 1005 101 1 1006 101 1 1007 101 1 1008 102 2 1009 102 2 1015 102 2 1016 103 2 1017 103 2 1018 103 2 1019 103 2 1020 103 2 1021 104 2 1022 104 2 1024 104 2 1025 105 2 1026 105 2 1027 105 2 1028 105 2 1029 105 2 1030 105 2 1031 106 2 1032 106 2 1033 106 2 1034 106 2 1035 106 2 1036 107 2 1037 107 2 1038 107 2 1040 107 2 1157 100 0 1179 105 2 1183 104 2 1193 105 2 1202 107 2 1203 107 2 update ignore t1 set id=id+1; select * from t1; id parent_id level 1001 100 0 1002 101 1 1003 101 1 1004 101 1 1005 101 1 1006 101 1 1007 101 1 1008 102 2 1010 102 2 1015 102 2 1016 103 2 1017 103 2 1018 103 2 1019 103 2 1020 103 2 1021 104 2 1023 104 2 1024 104 2 1025 105 2 1026 105 2 1027 105 2 1028 105 2 1029 105 2 1030 105 2 1031 106 2 1032 106 2 1033 106 2 1034 106 2 1035 106 2 1036 107 2 1037 107 2 1039 107 2 1041 107 2 1158 100 0 1180 105 2 1184 104 2 1194 105 2 1202 107 2 1204 107 2 update ignore t1 set id=1023 where id=1010; select * from t1 where parent_id=102; id parent_id level 1008 102 2 1010 102 2 1015 102 2 explain select level from t1 where level=1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref level level 1 const # Using index explain select level,id from t1 where level=1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref level level 1 const # Using index explain select level,id,parent_id from t1 where level=1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref level level 1 const # select level,id from t1 where level=1; level id 1 1002 1 1003 1 1004 1 1005 1 1006 1 1007 select level,id,parent_id from t1 where level=1; level id parent_id 1 1002 101 1 1003 101 1 1004 101 1 1005 101 1 1006 101 1 1007 101 optimize table t1; Table Op Msg_type Msg_text test.t1 optimize note Table does not support optimize, doing recreate + analyze instead test.t1 optimize status OK show keys from t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 0 PRIMARY 1 id A # NULL NULL BTREE t1 1 parent_id 1 parent_id A # NULL NULL BTREE t1 1 level 1 level A # NULL NULL BTREE drop table t1; CREATE TABLE t1 ( gesuchnr int(11) DEFAULT '0' NOT NULL, benutzer_id int(11) DEFAULT '0' NOT NULL, PRIMARY KEY (gesuchnr,benutzer_id) ) engine=innodb; replace into t1 (gesuchnr,benutzer_id) values (2,1); replace into t1 (gesuchnr,benutzer_id) values (1,1); replace into t1 (gesuchnr,benutzer_id) values (1,1); select * from t1; gesuchnr benutzer_id 1 1 2 1 drop table t1; create table t1 (a int) engine=innodb; insert into t1 values (1), (2); optimize table t1; Table Op Msg_type Msg_text test.t1 optimize note Table does not support optimize, doing recreate + analyze instead test.t1 optimize status OK delete from t1 where a = 1; select * from t1; a 2 check table t1; Table Op Msg_type Msg_text test.t1 check status OK drop table t1; create table t1 (a int,b varchar(20)) engine=innodb; insert into t1 values (1,""), (2,"testing"); delete from t1 where a = 1; select * from t1; a b 2 testing create index skr on t1 (a); insert into t1 values (3,""), (4,"testing"); analyze table t1; Table Op Msg_type Msg_text test.t1 analyze status OK show keys from t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 1 skr 1 a A # NULL NULL YES BTREE drop table t1; create table t1 (a int,b varchar(20),key(a)) engine=innodb; insert into t1 values (1,""), (2,"testing"); select * from t1 where a = 1; a b 1 drop table t1; create table t1 (n int not null primary key) engine=innodb; set autocommit=0; insert into t1 values (4); rollback; select n, "after rollback" from t1; n after rollback insert into t1 values (4); commit; select n, "after commit" from t1; n after commit 4 after commit commit; insert into t1 values (5); insert into t1 values (4); ERROR 23000: Duplicate entry '4' for key 'PRIMARY' commit; select n, "after commit" from t1; n after commit 4 after commit 5 after commit set autocommit=1; insert into t1 values (6); insert into t1 values (4); ERROR 23000: Duplicate entry '4' for key 'PRIMARY' select n from t1; n 4 5 6 set autocommit=0; begin; savepoint `my_savepoint`; insert into t1 values (7); savepoint `savept2`; insert into t1 values (3); select n from t1; n 3 4 5 6 7 savepoint savept3; rollback to savepoint savept2; rollback to savepoint savept3; ERROR 42000: SAVEPOINT savept3 does not exist rollback to savepoint savept2; release savepoint `my_savepoint`; select n from t1; n 4 5 6 7 rollback to savepoint `my_savepoint`; ERROR 42000: SAVEPOINT my_savepoint does not exist rollback to savepoint savept2; ERROR 42000: SAVEPOINT savept2 does not exist insert into t1 values (8); savepoint sv; commit; savepoint sv; set autocommit=1; rollback; drop table t1; create table t1 (n int not null primary key) engine=innodb; start transaction; insert into t1 values (4); flush tables with read lock; commit; unlock tables; commit; select * from t1; n 4 drop table t1; create table t1 ( id int NOT NULL PRIMARY KEY, nom varchar(64)) engine=innodb; begin; insert into t1 values(1,'hamdouni'); select id as afterbegin_id,nom as afterbegin_nom from t1; afterbegin_id afterbegin_nom 1 hamdouni rollback; select id as afterrollback_id,nom as afterrollback_nom from t1; afterrollback_id afterrollback_nom set autocommit=0; insert into t1 values(2,'mysql'); select id as afterautocommit0_id,nom as afterautocommit0_nom from t1; afterautocommit0_id afterautocommit0_nom 2 mysql rollback; select id as afterrollback_id,nom as afterrollback_nom from t1; afterrollback_id afterrollback_nom set autocommit=1; drop table t1; CREATE TABLE t1 (id char(8) not null primary key, val int not null) engine=innodb; insert into t1 values ('pippo', 12); insert into t1 values ('pippo', 12); ERROR 23000: Duplicate entry 'pippo' for key 'PRIMARY' delete from t1; delete from t1 where id = 'pippo'; select * from t1; id val insert into t1 values ('pippo', 12); set autocommit=0; delete from t1; rollback; select * from t1; id val pippo 12 delete from t1; commit; select * from t1; id val drop table t1; create table t1 (a integer) engine=innodb; start transaction; rename table t1 to t2; create table t1 (b integer) engine=innodb; insert into t1 values (1); rollback; drop table t1; rename table t2 to t1; drop table t1; set autocommit=1; CREATE TABLE t1 (ID INTEGER NOT NULL PRIMARY KEY, NAME VARCHAR(64)) ENGINE=innodb; INSERT INTO t1 VALUES (1, 'Jochen'); select * from t1; ID NAME 1 Jochen drop table t1; CREATE TABLE t1 ( _userid VARCHAR(60) NOT NULL PRIMARY KEY) ENGINE=innodb; set autocommit=0; INSERT INTO t1 SET _userid='marc@anyware.co.uk'; COMMIT; SELECT * FROM t1; _userid marc@anyware.co.uk SELECT _userid FROM t1 WHERE _userid='marc@anyware.co.uk'; _userid marc@anyware.co.uk drop table t1; set autocommit=1; CREATE TABLE t1 ( user_id int(10) DEFAULT '0' NOT NULL, name varchar(100), phone varchar(100), ref_email varchar(100) DEFAULT '' NOT NULL, detail varchar(200), PRIMARY KEY (user_id,ref_email) )engine=innodb; INSERT INTO t1 VALUES (10292,'sanjeev','29153373','sansh777@hotmail.com','xxx'),(10292,'shirish','2333604','shirish@yahoo.com','ddsds'),(10292,'sonali','323232','sonali@bolly.com','filmstar'); select * from t1 where user_id=10292; user_id name phone ref_email detail 10292 sanjeev 29153373 sansh777@hotmail.com xxx 10292 shirish 2333604 shirish@yahoo.com ddsds 10292 sonali 323232 sonali@bolly.com filmstar INSERT INTO t1 VALUES (10291,'sanjeev','29153373','sansh777@hotmail.com','xxx'),(10293,'shirish','2333604','shirish@yahoo.com','ddsds'); select * from t1 where user_id=10292; user_id name phone ref_email detail 10292 sanjeev 29153373 sansh777@hotmail.com xxx 10292 shirish 2333604 shirish@yahoo.com ddsds 10292 sonali 323232 sonali@bolly.com filmstar select * from t1 where user_id>=10292; user_id name phone ref_email detail 10292 sanjeev 29153373 sansh777@hotmail.com xxx 10292 shirish 2333604 shirish@yahoo.com ddsds 10292 sonali 323232 sonali@bolly.com filmstar 10293 shirish 2333604 shirish@yahoo.com ddsds select * from t1 where user_id>10292; user_id name phone ref_email detail 10293 shirish 2333604 shirish@yahoo.com ddsds select * from t1 where user_id<10292; user_id name phone ref_email detail 10291 sanjeev 29153373 sansh777@hotmail.com xxx drop table t1; CREATE TABLE t1 (a int not null, b int not null,c int not null, key(a),primary key(a,b), unique(c),key(a),unique(b)); show index from t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 0 PRIMARY 1 a A # NULL NULL BTREE t1 0 PRIMARY 2 b A # NULL NULL BTREE t1 0 c 1 c A # NULL NULL BTREE t1 0 b 1 b A # NULL NULL BTREE t1 1 a 1 a A # NULL NULL BTREE t1 1 a_2 1 a A # NULL NULL BTREE drop table t1; create table t1 (col1 int not null, col2 char(4) not null, primary key(col1)); alter table t1 engine=innodb; insert into t1 values ('1','1'),('5','2'),('2','3'),('3','4'),('4','4'); select * from t1; col1 col2 1 1 2 3 3 4 4 4 5 2 update t1 set col2='7' where col1='4'; select * from t1; col1 col2 1 1 2 3 3 4 4 7 5 2 alter table t1 add co3 int not null; select * from t1; col1 col2 co3 1 1 0 2 3 0 3 4 0 4 7 0 5 2 0 update t1 set col2='9' where col1='2'; select * from t1; col1 col2 co3 1 1 0 2 9 0 3 4 0 4 7 0 5 2 0 drop table t1; create table t1 (a int not null , b int, primary key (a)) engine = innodb; create table t2 (a int not null , b int, primary key (a)) engine = myisam; insert into t1 VALUES (1,3) , (2,3), (3,3); select * from t1; a b 1 3 2 3 3 3 insert into t2 select * from t1; select * from t2; a b 1 3 2 3 3 3 delete from t1 where b = 3; select * from t1; a b insert into t1 select * from t2; select * from t1; a b 1 3 2 3 3 3 select * from t2; a b 1 3 2 3 3 3 drop table t1,t2; CREATE TABLE t1 ( user_name varchar(12), password text, subscribed char(1), user_id int(11) DEFAULT '0' NOT NULL, quota bigint(20), weight double, access_date date, access_time time, approved datetime, dummy_primary_key int(11) NOT NULL auto_increment, PRIMARY KEY (dummy_primary_key) ) ENGINE=innodb; INSERT INTO t1 VALUES ('user_0','somepassword','N',0,0,0,'2000-09-07','23:06:59','2000-09-07 23:06:59',1); INSERT INTO t1 VALUES ('user_1','somepassword','Y',1,1,1,'2000-09-07','23:06:59','2000-09-07 23:06:59',2); INSERT INTO t1 VALUES ('user_2','somepassword','N',2,2,1.4142135623731,'2000-09-07','23:06:59','2000-09-07 23:06:59',3); INSERT INTO t1 VALUES ('user_3','somepassword','Y',3,3,1.7320508075689,'2000-09-07','23:06:59','2000-09-07 23:06:59',4); INSERT INTO t1 VALUES ('user_4','somepassword','N',4,4,2,'2000-09-07','23:06:59','2000-09-07 23:06:59',5); select user_name, password , subscribed, user_id, quota, weight, access_date, access_time, approved, dummy_primary_key from t1 order by user_name; user_name password subscribed user_id quota weight access_date access_time approved dummy_primary_key user_0 somepassword N 0 0 0 2000-09-07 23:06:59 2000-09-07 23:06:59 1 user_1 somepassword Y 1 1 1 2000-09-07 23:06:59 2000-09-07 23:06:59 2 user_2 somepassword N 2 2 1.4142135623731 2000-09-07 23:06:59 2000-09-07 23:06:59 3 user_3 somepassword Y 3 3 1.7320508075689 2000-09-07 23:06:59 2000-09-07 23:06:59 4 user_4 somepassword N 4 4 2 2000-09-07 23:06:59 2000-09-07 23:06:59 5 drop table t1; CREATE TABLE t1 ( id int(11) NOT NULL auto_increment, parent_id int(11) DEFAULT '0' NOT NULL, level tinyint(4) DEFAULT '0' NOT NULL, KEY (id), KEY parent_id (parent_id), KEY level (level) ) engine=innodb; INSERT INTO t1 VALUES (1,0,0),(3,1,1),(4,1,1),(8,2,2),(9,2,2),(17,3,2),(22,4,2),(24,4,2),(28,5,2),(29,5,2),(30,5,2),(31,6,2),(32,6,2),(33,6,2),(203,7,2),(202,7,2),(20,3,2),(157,0,0),(193,5,2),(40,7,2),(2,1,1),(15,2,2),(6,1,1),(34,6,2),(35,6,2),(16,3,2),(7,1,1),(36,7,2),(18,3,2),(26,5,2),(27,5,2),(183,4,2),(38,7,2),(25,5,2),(37,7,2),(21,4,2),(19,3,2),(5,1,1); INSERT INTO t1 values (179,5,2); update t1 set parent_id=parent_id+100; select * from t1 where parent_id=102; id parent_id level 8 102 2 9 102 2 15 102 2 update t1 set id=id+1000; update t1 set id=1024 where id=1009; select * from t1; id parent_id level 1001 100 0 1003 101 1 1004 101 1 1008 102 2 1024 102 2 1017 103 2 1022 104 2 1024 104 2 1028 105 2 1029 105 2 1030 105 2 1031 106 2 1032 106 2 1033 106 2 1203 107 2 1202 107 2 1020 103 2 1157 100 0 1193 105 2 1040 107 2 1002 101 1 1015 102 2 1006 101 1 1034 106 2 1035 106 2 1016 103 2 1007 101 1 1036 107 2 1018 103 2 1026 105 2 1027 105 2 1183 104 2 1038 107 2 1025 105 2 1037 107 2 1021 104 2 1019 103 2 1005 101 1 1179 105 2 update ignore t1 set id=id+1; select * from t1; id parent_id level 1002 100 0 1004 101 1 1005 101 1 1009 102 2 1025 102 2 1018 103 2 1023 104 2 1025 104 2 1029 105 2 1030 105 2 1031 105 2 1032 106 2 1033 106 2 1034 106 2 1204 107 2 1203 107 2 1021 103 2 1158 100 0 1194 105 2 1041 107 2 1003 101 1 1016 102 2 1007 101 1 1035 106 2 1036 106 2 1017 103 2 1008 101 1 1037 107 2 1019 103 2 1027 105 2 1028 105 2 1184 104 2 1039 107 2 1026 105 2 1038 107 2 1022 104 2 1020 103 2 1006 101 1 1180 105 2 update ignore t1 set id=1023 where id=1010; select * from t1 where parent_id=102; id parent_id level 1009 102 2 1025 102 2 1016 102 2 explain select level from t1 where level=1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref level level 1 const # Using index select level,id from t1 where level=1; level id 1 1004 1 1005 1 1003 1 1007 1 1008 1 1006 select level,id,parent_id from t1 where level=1; level id parent_id 1 1004 101 1 1005 101 1 1003 101 1 1007 101 1 1008 101 1 1006 101 select level,id from t1 where level=1 order by id; level id 1 1003 1 1004 1 1005 1 1006 1 1007 1 1008 delete from t1 where level=1; select * from t1; id parent_id level 1002 100 0 1009 102 2 1025 102 2 1018 103 2 1023 104 2 1025 104 2 1029 105 2 1030 105 2 1031 105 2 1032 106 2 1033 106 2 1034 106 2 1204 107 2 1203 107 2 1021 103 2 1158 100 0 1194 105 2 1041 107 2 1016 102 2 1035 106 2 1036 106 2 1017 103 2 1037 107 2 1019 103 2 1027 105 2 1028 105 2 1184 104 2 1039 107 2 1026 105 2 1038 107 2 1022 104 2 1020 103 2 1180 105 2 drop table t1; CREATE TABLE t1 ( sca_code char(6) NOT NULL, cat_code char(6) NOT NULL, sca_desc varchar(50), lan_code char(2) NOT NULL, sca_pic varchar(100), sca_sdesc varchar(50), sca_sch_desc varchar(16), PRIMARY KEY (sca_code, cat_code, lan_code), INDEX sca_pic (sca_pic) ) engine = innodb ; INSERT INTO t1 ( sca_code, cat_code, sca_desc, lan_code, sca_pic, sca_sdesc, sca_sch_desc) VALUES ( 'PD', 'J', 'PENDANT', 'EN', NULL, NULL, 'PENDANT'),( 'RI', 'J', 'RING', 'EN', NULL, NULL, 'RING'),( 'QQ', 'N', 'RING', 'EN', 'not null', NULL, 'RING'); select count(*) from t1 where sca_code = 'PD'; count(*) 1 select count(*) from t1 where sca_code <= 'PD'; count(*) 1 select count(*) from t1 where sca_pic is null; count(*) 2 alter table t1 drop index sca_pic, add index sca_pic (cat_code, sca_pic); select count(*) from t1 where sca_code='PD' and sca_pic is null; count(*) 1 select count(*) from t1 where cat_code='E'; count(*) 0 alter table t1 drop index sca_pic, add index (sca_pic, cat_code); select count(*) from t1 where sca_code='PD' and sca_pic is null; count(*) 1 select count(*) from t1 where sca_pic >= 'n'; count(*) 1 select sca_pic from t1 where sca_pic is null; sca_pic NULL NULL update t1 set sca_pic="test" where sca_pic is null; delete from t1 where sca_code='pd'; drop table t1; set @a:=now(); CREATE TABLE t1 (a int not null, b timestamp not null, primary key (a)) engine=innodb; insert into t1 (a) values(1),(2),(3); select t1.a from t1 natural join t1 as t2 where t1.b >= @a order by t1.a; a 1 2 3 select a from t1 natural join t1 as t2 where b >= @a order by a; a 1 2 3 update t1 set a=5 where a=1; select a from t1; a 2 3 5 drop table t1; create table t1 (a varchar(100) not null, primary key(a), b int not null) engine=innodb; insert into t1 values("hello",1),("world",2); select * from t1 order by b desc; a b world 2 hello 1 optimize table t1; Table Op Msg_type Msg_text test.t1 optimize note Table does not support optimize, doing recreate + analyze instead test.t1 optimize status OK show keys from t1; Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment t1 0 PRIMARY 1 a A # NULL NULL BTREE drop table t1; create table t1 (i int, j int ) ENGINE=innodb; insert into t1 values (1,2); select * from t1 where i=1 and j=2; i j 1 2 create index ax1 on t1 (i,j); select * from t1 where i=1 and j=2; i j 1 2 drop table t1; CREATE TABLE t1 ( a int3 unsigned NOT NULL, b int1 unsigned NOT NULL, UNIQUE (a, b) ) ENGINE = innodb; INSERT INTO t1 VALUES (1, 1); SELECT MIN(B),MAX(b) FROM t1 WHERE t1.a = 1; MIN(B) MAX(b) 1 1 drop table t1; CREATE TABLE t1 (a int unsigned NOT NULL) engine=innodb; INSERT INTO t1 VALUES (1); SELECT * FROM t1; a 1 DROP TABLE t1; create table t1 (a int primary key,b int, c int, d int, e int, f int, g int, h int, i int, j int, k int, l int, m int, n int, o int, p int, q int, r int, s int, t int, u int, v int, w int, x int, y int, z int, a1 int, a2 int, a3 int, a4 int, a5 int, a6 int, a7 int, a8 int, a9 int, b1 int, b2 int, b3 int, b4 int, b5 int, b6 int) engine = innodb; insert into t1 values (1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1); explain select * from t1 where a > 0 and a < 50; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL # Using where drop table t1; create table t1 (id int NOT NULL,id2 int NOT NULL,id3 int NOT NULL,dummy1 char(30),primary key (id,id2),index index_id3 (id3)) engine=innodb; insert into t1 values (0,0,0,'ABCDEFGHIJ'),(2,2,2,'BCDEFGHIJK'),(1,1,1,'CDEFGHIJKL'); LOCK TABLES t1 WRITE; insert into t1 values (99,1,2,'D'),(1,1,2,'D'); ERROR 23000: Duplicate entry '1-1' for key 'PRIMARY' select id from t1; id 0 1 2 select id from t1; id 0 1 2 UNLOCK TABLES; DROP TABLE t1; create table t1 (id int NOT NULL,id2 int NOT NULL,id3 int NOT NULL,dummy1 char(30),primary key (id,id2),index index_id3 (id3)) engine=innodb; insert into t1 values (0,0,0,'ABCDEFGHIJ'),(2,2,2,'BCDEFGHIJK'),(1,1,1,'CDEFGHIJKL'); LOCK TABLES t1 WRITE; begin; insert into t1 values (99,1,2,'D'),(1,1,2,'D'); ERROR 23000: Duplicate entry '1-1' for key 'PRIMARY' select id from t1; id 0 1 2 insert ignore into t1 values (100,1,2,'D'),(1,1,99,'D'); commit; select id,id3 from t1; id id3 0 0 1 1 2 2 100 2 UNLOCK TABLES; DROP TABLE t1; create table t1 (a char(20), unique (a(5))) engine=innodb; drop table t1; create table t1 (a char(20), index (a(5))) engine=innodb; show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` char(20) DEFAULT NULL, KEY `a` (`a`(5)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create temporary table t1 (a int not null auto_increment, primary key(a)) engine=innodb; insert into t1 values (NULL),(NULL),(NULL); delete from t1 where a=3; insert into t1 values (NULL); select * from t1; a 1 2 4 alter table t1 add b int; select * from t1; a b 1 NULL 2 NULL 4 NULL drop table t1; create table t1 ( id int auto_increment primary key, name varchar(32) not null, value text not null, uid int not null, unique key(name,uid) ) engine=innodb; insert into t1 values (1,'one','one value',101), (2,'two','two value',102),(3,'three','three value',103); set insert_id=5; replace into t1 (value,name,uid) values ('other value','two',102); delete from t1 where uid=102; set insert_id=5; replace into t1 (value,name,uid) values ('other value','two',102); set insert_id=6; replace into t1 (value,name,uid) values ('other value','two',102); select * from t1; id name value uid 1 one one value 101 3 three three value 103 6 two other value 102 drop table t1; create database mysqltest; create table mysqltest.t1 (a int not null) engine= innodb; insert into mysqltest.t1 values(1); create table mysqltest.t2 (a int not null) engine= myisam; insert into mysqltest.t2 values(1); create table mysqltest.t3 (a int not null) engine= heap; insert into mysqltest.t3 values(1); commit; drop database mysqltest; show tables from mysqltest; ERROR 42000: Unknown database 'mysqltest' set autocommit=0; create table t1 (a int not null) engine= innodb; insert into t1 values(1),(2); truncate table t1; commit; truncate table t1; truncate table t1; select * from t1; a insert into t1 values(1),(2); delete from t1; select * from t1; a commit; drop table t1; set autocommit=1; create table t1 (a int not null) engine= innodb; insert into t1 values(1),(2); truncate table t1; insert into t1 values(1),(2); select * from t1; a 1 2 truncate table t1; insert into t1 values(1),(2); delete from t1; select * from t1; a drop table t1; create table t1 (a int not null, b int not null, c int not null, primary key (a),key(b)) engine=innodb; insert into t1 values (3,3,3),(1,1,1),(2,2,2),(4,4,4); explain select * from t1 order by a; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL PRIMARY 4 NULL # explain select * from t1 order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL # Using filesort explain select * from t1 order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL # Using filesort explain select a from t1 order by a; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL PRIMARY 4 NULL # Using index explain select b from t1 order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 4 NULL # Using index explain select a,b from t1 order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 4 NULL # Using index explain select a,b from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 4 NULL # Using index explain select a,b,c from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL # drop table t1; create table t1 (t int not null default 1, key (t)) engine=innodb; desc t1; Field Type Null Key Default Extra t int(11) NO MUL 1 drop table t1; CREATE TABLE t1 ( number bigint(20) NOT NULL default '0', cname char(15) NOT NULL default '', carrier_id smallint(6) NOT NULL default '0', privacy tinyint(4) NOT NULL default '0', last_mod_date timestamp NOT NULL, last_mod_id smallint(6) NOT NULL default '0', last_app_date timestamp NOT NULL, last_app_id smallint(6) default '-1', version smallint(6) NOT NULL default '0', assigned_scps int(11) default '0', status tinyint(4) default '0' ) ENGINE=InnoDB; INSERT INTO t1 VALUES (4077711111,'SeanWheeler',90,2,20020111112846,500,00000000000000,-1,2,3,1); INSERT INTO t1 VALUES (9197722223,'berry',90,3,20020111112809,500,20020102114532,501,4,10,0); INSERT INTO t1 VALUES (650,'San Francisco',0,0,20011227111336,342,00000000000000,-1,1,24,1); INSERT INTO t1 VALUES (302467,'Sue\'s Subshop',90,3,20020109113241,500,20020102115111,501,7,24,0); INSERT INTO t1 VALUES (6014911113,'SudzCarwash',520,1,20020102115234,500,20020102115259,501,33,32768,0); INSERT INTO t1 VALUES (333,'tubs',99,2,20020109113440,501,20020109113440,500,3,10,0); CREATE TABLE t2 ( number bigint(20) NOT NULL default '0', cname char(15) NOT NULL default '', carrier_id smallint(6) NOT NULL default '0', privacy tinyint(4) NOT NULL default '0', last_mod_date timestamp NOT NULL, last_mod_id smallint(6) NOT NULL default '0', last_app_date timestamp NOT NULL, last_app_id smallint(6) default '-1', version smallint(6) NOT NULL default '0', assigned_scps int(11) default '0', status tinyint(4) default '0' ) ENGINE=InnoDB; INSERT INTO t2 VALUES (4077711111,'SeanWheeler',0,2,20020111112853,500,00000000000000,-1,2,3,1); INSERT INTO t2 VALUES (9197722223,'berry',90,3,20020111112818,500,20020102114532,501,4,10,0); INSERT INTO t2 VALUES (650,'San Francisco',90,0,20020109113158,342,00000000000000,-1,1,24,1); INSERT INTO t2 VALUES (333,'tubs',99,2,20020109113453,501,20020109113453,500,3,10,0); select * from t1; number cname carrier_id privacy last_mod_date last_mod_id last_app_date last_app_id version assigned_scps status 4077711111 SeanWheeler 90 2 2002-01-11 11:28:46 500 0000-00-00 00:00:00 -1 2 3 1 9197722223 berry 90 3 2002-01-11 11:28:09 500 2002-01-02 11:45:32 501 4 10 0 650 San Francisco 0 0 2001-12-27 11:13:36 342 0000-00-00 00:00:00 -1 1 24 1 302467 Sue's Subshop 90 3 2002-01-09 11:32:41 500 2002-01-02 11:51:11 501 7 24 0 6014911113 SudzCarwash 520 1 2002-01-02 11:52:34 500 2002-01-02 11:52:59 501 33 32768 0 333 tubs 99 2 2002-01-09 11:34:40 501 2002-01-09 11:34:40 500 3 10 0 select * from t2; number cname carrier_id privacy last_mod_date last_mod_id last_app_date last_app_id version assigned_scps status 4077711111 SeanWheeler 0 2 2002-01-11 11:28:53 500 0000-00-00 00:00:00 -1 2 3 1 9197722223 berry 90 3 2002-01-11 11:28:18 500 2002-01-02 11:45:32 501 4 10 0 650 San Francisco 90 0 2002-01-09 11:31:58 342 0000-00-00 00:00:00 -1 1 24 1 333 tubs 99 2 2002-01-09 11:34:53 501 2002-01-09 11:34:53 500 3 10 0 delete t1, t2 from t1 left join t2 on t1.number=t2.number where (t1.carrier_id=90 and t1.number=t2.number) or (t2.carrier_id=90 and t1.number=t2.number) or (t1.carrier_id=90 and t2.number is null); select * from t1; number cname carrier_id privacy last_mod_date last_mod_id last_app_date last_app_id version assigned_scps status 6014911113 SudzCarwash 520 1 2002-01-02 11:52:34 500 2002-01-02 11:52:59 501 33 32768 0 333 tubs 99 2 2002-01-09 11:34:40 501 2002-01-09 11:34:40 500 3 10 0 select * from t2; number cname carrier_id privacy last_mod_date last_mod_id last_app_date last_app_id version assigned_scps status 333 tubs 99 2 2002-01-09 11:34:53 501 2002-01-09 11:34:53 500 3 10 0 select * from t2; number cname carrier_id privacy last_mod_date last_mod_id last_app_date last_app_id version assigned_scps status 333 tubs 99 2 2002-01-09 11:34:53 501 2002-01-09 11:34:53 500 3 10 0 drop table t1,t2; create table t1 (id int unsigned not null auto_increment, code tinyint unsigned not null, name char(20) not null, primary key (id), key (code), unique (name)) engine=innodb; BEGIN; SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE; SELECT @@tx_isolation,@@global.tx_isolation; @@tx_isolation @@global.tx_isolation SERIALIZABLE REPEATABLE-READ insert into t1 (code, name) values (1, 'Tim'), (1, 'Monty'), (2, 'David'); select id, code, name from t1 order by id; id code name 1 1 Tim 2 1 Monty 3 2 David COMMIT; BEGIN; SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ; insert into t1 (code, name) values (2, 'Erik'), (3, 'Sasha'); select id, code, name from t1 order by id; id code name 1 1 Tim 2 1 Monty 3 2 David 4 2 Erik 5 3 Sasha COMMIT; SET binlog_format='MIXED'; BEGIN; SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; insert into t1 (code, name) values (3, 'Jeremy'), (4, 'Matt'); select id, code, name from t1 order by id; id code name 1 1 Tim 2 1 Monty 3 2 David 4 2 Erik 5 3 Sasha 6 3 Jeremy 7 4 Matt COMMIT; DROP TABLE t1; create table t1 (n int(10), d int(10)) engine=innodb; create table t2 (n int(10), d int(10)) engine=innodb; insert into t1 values(1,1),(1,2); insert into t2 values(1,10),(2,20); UPDATE t1,t2 SET t1.d=t2.d,t2.d=30 WHERE t1.n=t2.n; select * from t1; n d 1 10 1 10 select * from t2; n d 1 30 2 20 drop table t1,t2; drop table if exists t1, t2; CREATE TABLE t1 (a int, PRIMARY KEY (a)); CREATE TABLE t2 (a int, PRIMARY KEY (a)) ENGINE=InnoDB; create trigger trg_del_t2 after delete on t2 for each row insert into t1 values (1); insert into t1 values (1); insert into t2 values (1),(2); delete t2 from t2; ERROR 23000: Duplicate entry '1' for key 'PRIMARY' select count(*) from t2 /* must be 2 as restored after rollback caused by the error */; count(*) 2 drop table t1, t2; drop table if exists t1, t2; CREATE TABLE t1 (a int, PRIMARY KEY (a)); CREATE TABLE t2 (a int, PRIMARY KEY (a)) ENGINE=InnoDB; create trigger trg_del_t2 after delete on t2 for each row insert into t1 values (1); insert into t1 values (1); insert into t2 values (1),(2); delete t2 from t2; ERROR 23000: Duplicate entry '1' for key 'PRIMARY' select count(*) from t2 /* must be 2 as restored after rollback caused by the error */; count(*) 2 drop table t1, t2; create table t1 (a int, b int) engine=innodb; insert into t1 values(20,null); select t2.b, ifnull(t2.b,"this is null") from t1 as t2 left join t1 as t3 on t2.b=t3.a; b ifnull(t2.b,"this is null") NULL this is null select t2.b, ifnull(t2.b,"this is null") from t1 as t2 left join t1 as t3 on t2.b=t3.a order by 1; b ifnull(t2.b,"this is null") NULL this is null insert into t1 values(10,null); select t2.b, ifnull(t2.b,"this is null") from t1 as t2 left join t1 as t3 on t2.b=t3.a order by 1; b ifnull(t2.b,"this is null") NULL this is null NULL this is null drop table t1; create table t1 (a varchar(10) not null) engine=myisam; create table t2 (b varchar(10) not null unique) engine=innodb; select t1.a from t1,t2 where t1.a=t2.b; a drop table t1,t2; create table t1 (a int not null, b int, primary key (a)) engine = innodb; create table t2 (a int not null, b int, primary key (a)) engine = innodb; insert into t1 values (10, 20); insert into t2 values (10, 20); update t1, t2 set t1.b = 150, t2.b = t1.b where t2.a = t1.a and t1.a = 10; drop table t1,t2; CREATE TABLE t1 (id INT NOT NULL, PRIMARY KEY (id)) ENGINE=INNODB; CREATE TABLE t2 (id INT PRIMARY KEY, t1_id INT, INDEX par_ind (t1_id), FOREIGN KEY (t1_id) REFERENCES t1(id) ON DELETE CASCADE ) ENGINE=INNODB; insert into t1 set id=1; insert into t2 set id=1, t1_id=1; delete t1,t2 from t1,t2 where t1.id=t2.t1_id; select * from t1; id select * from t2; id t1_id drop table t2,t1; CREATE TABLE t1(id INT NOT NULL, PRIMARY KEY (id)) ENGINE=INNODB; CREATE TABLE t2(id INT PRIMARY KEY, t1_id INT, INDEX par_ind (t1_id) ) ENGINE=INNODB; INSERT INTO t1 VALUES(1); INSERT INTO t2 VALUES(1, 1); SELECT * from t1; id 1 UPDATE t1,t2 SET t1.id=t1.id+1, t2.t1_id=t1.id+1; SELECT * from t1; id 2 UPDATE t1,t2 SET t1.id=t1.id+1 where t1.id!=t2.id; SELECT * from t1; id 3 DROP TABLE t1,t2; set autocommit=0; CREATE TABLE t1 (id CHAR(15) NOT NULL, value CHAR(40) NOT NULL, PRIMARY KEY(id)) ENGINE=InnoDB; CREATE TABLE t2 (id CHAR(15) NOT NULL, value CHAR(40) NOT NULL, PRIMARY KEY(id)) ENGINE=InnoDB; CREATE TABLE t3 (id1 CHAR(15) NOT NULL, id2 CHAR(15) NOT NULL, PRIMARY KEY(id1, id2)) ENGINE=InnoDB; INSERT INTO t3 VALUES("my-test-1", "my-test-2"); COMMIT; INSERT INTO t1 VALUES("this-key", "will disappear"); INSERT INTO t2 VALUES("this-key", "will also disappear"); DELETE FROM t3 WHERE id1="my-test-1"; SELECT * FROM t1; id value this-key will disappear SELECT * FROM t2; id value this-key will also disappear SELECT * FROM t3; id1 id2 ROLLBACK; SELECT * FROM t1; id value SELECT * FROM t2; id value SELECT * FROM t3; id1 id2 my-test-1 my-test-2 SELECT * FROM t3 WHERE id1="my-test-1" LOCK IN SHARE MODE; id1 id2 my-test-1 my-test-2 COMMIT; set autocommit=1; DROP TABLE t1,t2,t3; CREATE TABLE t1 (a int not null primary key, b int not null, unique (b)) engine=innodb; INSERT INTO t1 values (1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(7,7),(8,8),(9,9); UPDATE t1 set a=a+100 where b between 2 and 3 and a < 1000; SELECT * from t1; a b 1 1 102 2 103 3 4 4 5 5 6 6 7 7 8 8 9 9 drop table t1; CREATE TABLE t2 ( NEXT_T BIGINT NOT NULL PRIMARY KEY) ENGINE=MyISAM; CREATE TABLE t1 ( B_ID INTEGER NOT NULL PRIMARY KEY) ENGINE=InnoDB; SET AUTOCOMMIT=0; INSERT INTO t1 ( B_ID ) VALUES ( 1 ); INSERT INTO t2 ( NEXT_T ) VALUES ( 1 ); ROLLBACK; Warnings: Warning 1196 Some non-transactional changed tables couldn't be rolled back SELECT * FROM t1; B_ID drop table t1,t2; create table t1 ( pk int primary key, parent int not null, child int not null, index (parent) ) engine = innodb; insert into t1 values (1,0,4), (2,1,3), (3,2,1), (4,1,2); select distinct parent,child from t1 order by parent; parent child 0 4 1 2 1 3 2 1 drop table t1; create table t1 (a int not null auto_increment primary key, b int, c int, key(c)) engine=innodb; create table t2 (a int not null auto_increment primary key, b int); insert into t1 (b) values (null),(null),(null),(null),(null),(null),(null); insert into t2 (a) select b from t1; insert into t1 (b) select b from t2; insert into t2 (a) select b from t1; insert into t1 (a) select b from t2; insert into t2 (a) select b from t1; insert into t1 (a) select b from t2; insert into t2 (a) select b from t1; insert into t1 (a) select b from t2; insert into t2 (a) select b from t1; insert into t1 (a) select b from t2; select count(*) from t1; count(*) 623 explain select * from t1 where c between 1 and 2500; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range c c 5 NULL # Using where update t1 set c=a; explain select * from t1 where c between 1 and 2500; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL c NULL NULL NULL # Using where drop table t1,t2; create table t1 (id int primary key auto_increment, fk int, index index_fk (fk)) engine=innodb; insert into t1 (id) values (null),(null),(null),(null),(null); update t1 set fk=69 where fk is null order by id limit 1; SELECT * from t1; id fk 2 NULL 3 NULL 4 NULL 5 NULL 1 69 drop table t1; create table t1 (a int not null, b int not null, key (a)); insert into t1 values (1,1),(1,2),(1,3),(3,1),(3,2),(3,3),(3,1),(3,2),(3,3),(2,1),(2,2),(2,3); SET @tmp=0; update t1 set b=(@tmp:=@tmp+1) order by a; update t1 set b=99 where a=1 order by b asc limit 1; update t1 set b=100 where a=1 order by b desc limit 2; update t1 set a=a+10+b where a=1 order by b; select * from t1 order by a,b; a b 2 4 2 5 2 6 3 7 3 8 3 9 3 10 3 11 3 12 13 2 111 100 111 100 drop table t1; create table t1 ( c char(8) not null ) engine=innodb; insert into t1 values ('0'),('1'),('2'),('3'),('4'),('5'),('6'),('7'),('8'),('9'); insert into t1 values ('A'),('B'),('C'),('D'),('E'),('F'); alter table t1 add b char(8) not null; alter table t1 add a char(8) not null; alter table t1 add primary key (a,b,c); update t1 set a=c, b=c; create table t2 (c char(8) not null, b char(8) not null, a char(8) not null, primary key(a,b,c)) engine=innodb; insert into t2 select * from t1; delete t1,t2 from t2,t1 where t1.a<'B' and t2.b=t1.b; drop table t1,t2; SET AUTOCOMMIT=1; create table t1 (a integer auto_increment primary key) engine=innodb; insert into t1 (a) values (NULL),(NULL); truncate table t1; insert into t1 (a) values (NULL),(NULL); SELECT * from t1; a 1 2 drop table t1; CREATE TABLE t1 (`id 1` INT NOT NULL, PRIMARY KEY (`id 1`)) ENGINE=INNODB; CREATE TABLE t2 (id INT PRIMARY KEY, t1_id INT, INDEX par_ind (t1_id), FOREIGN KEY (`t1_id`) REFERENCES `t1`(`id 1`) ON DELETE CASCADE ) ENGINE=INNODB; drop table t2,t1; create table `t1` (`id` int( 11 ) not null ,primary key ( `id` )) engine = innodb; insert into `t1`values ( 1 ) ; create table `t2` (`id` int( 11 ) not null default '0',unique key `id` ( `id` ) ,constraint `t1_id_fk` foreign key ( `id` ) references `t1` (`id` )) engine = innodb; insert into `t2`values ( 1 ) ; create table `t3` (`id` int( 11 ) not null default '0',key `id` ( `id` ) ,constraint `t2_id_fk` foreign key ( `id` ) references `t2` (`id` )) engine = innodb; insert into `t3`values ( 1 ) ; delete t3,t2,t1 from t1,t2,t3 where t1.id =1 and t2.id = t1.id and t3.id = t2.id; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`)) update t1,t2,t3 set t3.id=5, t2.id=6, t1.id=7 where t1.id =1 and t2.id = t1.id and t3.id = t2.id; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`)) update t3 set t3.id=7 where t1.id =1 and t2.id = t1.id and t3.id = t2.id; ERROR 42S22: Unknown column 't1.id' in 'where clause' drop table t3,t2,t1; create table t1( id int primary key, pid int, index(pid), foreign key(pid) references t1(id) on delete cascade) engine=innodb; insert into t1 values(0,0),(1,0),(2,1),(3,2),(4,3),(5,4),(6,5),(7,6), (8,7),(9,8),(10,9),(11,10),(12,11),(13,12),(14,13),(15,14); delete from t1 where id=0; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t1`, CONSTRAINT `t1_ibfk_1` FOREIGN KEY (`pid`) REFERENCES `t1` (`id`) ON DELETE CASCADE) delete from t1 where id=15; delete from t1 where id=0; drop table t1; CREATE TABLE t1 (col1 int(1))ENGINE=InnoDB; CREATE TABLE t2 (col1 int(1),stamp TIMESTAMP,INDEX stamp_idx (stamp))ENGINE=InnoDB; insert into t1 values (1),(2),(3); insert into t2 values (1, 20020204130000),(2, 20020204130000),(4,20020204310000 ),(5,20020204230000); Warnings: Warning 1265 Data truncated for column 'stamp' at row 3 SELECT col1 FROM t1 UNION SELECT col1 FROM t2 WHERE stamp < '20020204120000' GROUP BY col1; col1 1 2 3 4 drop table t1,t2; CREATE TABLE t1 ( `id` int(10) unsigned NOT NULL auto_increment, `id_object` int(10) unsigned default '0', `id_version` int(10) unsigned NOT NULL default '1', `label` varchar(100) NOT NULL default '', `description` text, PRIMARY KEY (`id`), KEY `id_object` (`id_object`), KEY `id_version` (`id_version`) ) ENGINE=InnoDB; INSERT INTO t1 VALUES("6", "3382", "9", "Test", NULL), ("7", "102", "5", "Le Pekin (Test)", NULL),("584", "1794", "4", "Test de resto", NULL),("837", "1822", "6", "Test 3", NULL),("1119", "3524", "1", "Societe Test", NULL),("1122", "3525", "1", "Fournisseur Test", NULL); CREATE TABLE t2 ( `id` int(10) unsigned NOT NULL auto_increment, `id_version` int(10) unsigned NOT NULL default '1', PRIMARY KEY (`id`), KEY `id_version` (`id_version`) ) ENGINE=InnoDB; INSERT INTO t2 VALUES("3524", "1"),("3525", "1"),("1794", "4"),("102", "5"),("1822", "6"),("3382", "9"); SELECT t2.id, t1.`label` FROM t2 INNER JOIN (SELECT t1.id_object as id_object FROM t1 WHERE t1.`label` LIKE '%test%') AS lbl ON (t2.id = lbl.id_object) INNER JOIN t1 ON (t2.id = t1.id_object); id label 3382 Test 102 Le Pekin (Test) 1794 Test de resto 1822 Test 3 3524 Societe Test 3525 Fournisseur Test drop table t1,t2; create table t1 (a int, b varchar(200), c text not null) checksum=1 engine=myisam; create table t2 (a int, b varchar(200), c text not null) checksum=0 engine=innodb; create table t3 (a int, b varchar(200), c text not null) checksum=1 engine=innodb; insert t1 values (1, "aaa", "bbb"), (NULL, "", "ccccc"), (0, NULL, ""); insert t2 select * from t1; insert t3 select * from t1; checksum table t1, t2, t3, t4 quick; Table Checksum test.t1 2948697075 test.t2 NULL test.t3 NULL test.t4 NULL Warnings: Error 1146 Table 'test.t4' doesn't exist checksum table t1, t2, t3, t4; Table Checksum test.t1 2948697075 test.t2 2948697075 test.t3 2948697075 test.t4 NULL Warnings: Error 1146 Table 'test.t4' doesn't exist checksum table t1, t2, t3, t4 extended; Table Checksum test.t1 2948697075 test.t2 2948697075 test.t3 2948697075 test.t4 NULL Warnings: Error 1146 Table 'test.t4' doesn't exist drop table t1,t2,t3; create table t1 (id int, name char(10) not null, name2 char(10) not null) engine=innodb; insert into t1 values(1,'first','fff'),(2,'second','sss'),(3,'third','ttt'); select trim(name2) from t1 union all select trim(name) from t1 union all select trim(id) from t1; trim(name2) fff sss ttt first second third 1 2 3 drop table t1; create table t1 (a int) engine=innodb; create table t2 like t1; drop table t1,t2; create table t1 (id int(11) not null, id2 int(11) not null, unique (id,id2)) engine=innodb; create table t2 (id int(11) not null, constraint t1_id_fk foreign key ( id ) references t1 (id)) engine = innodb; show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `id` int(11) NOT NULL, `id2` int(11) NOT NULL, UNIQUE KEY `id` (`id`,`id2`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, KEY `t1_id_fk` (`id`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 create index id on t2 (id); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, KEY `id` (`id`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 create index id2 on t2 (id); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, KEY `id` (`id`), KEY `id2` (`id`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop index id2 on t2; drop index id on t2; Got one of the listed errors show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, KEY `id` (`id`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (id int(11) not null, id2 int(11) not null, constraint t1_id_fk foreign key (id,id2) references t1 (id,id2)) engine = innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, `id2` int(11) NOT NULL, KEY `t1_id_fk` (`id`,`id2`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`, `id2`) REFERENCES `t1` (`id`, `id2`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 create unique index id on t2 (id,id2); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, `id2` int(11) NOT NULL, UNIQUE KEY `id` (`id`,`id2`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`, `id2`) REFERENCES `t1` (`id`, `id2`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (id int(11) not null, id2 int(11) not null, unique (id,id2),constraint t1_id_fk foreign key (id2,id) references t1 (id,id2)) engine = innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, `id2` int(11) NOT NULL, UNIQUE KEY `id` (`id`,`id2`), KEY `t1_id_fk` (`id2`,`id`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id2`, `id`) REFERENCES `t1` (`id`, `id2`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (id int(11) not null, id2 int(11) not null, unique (id,id2), constraint t1_id_fk foreign key (id) references t1 (id)) engine = innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, `id2` int(11) NOT NULL, UNIQUE KEY `id` (`id`,`id2`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (id int(11) not null, id2 int(11) not null, unique (id,id2),constraint t1_id_fk foreign key (id2,id) references t1 (id,id2)) engine = innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL, `id2` int(11) NOT NULL, UNIQUE KEY `id` (`id`,`id2`), KEY `t1_id_fk` (`id2`,`id`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id2`, `id`) REFERENCES `t1` (`id`, `id2`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (id int(11) not null auto_increment, id2 int(11) not null, constraint t1_id_fk foreign key (id) references t1 (id), primary key (id), index (id,id2)) engine = innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL AUTO_INCREMENT, `id2` int(11) NOT NULL, PRIMARY KEY (`id`), KEY `id` (`id`,`id2`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (id int(11) not null auto_increment, id2 int(11) not null, constraint t1_id_fk foreign key (id) references t1 (id)) engine= innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL AUTO_INCREMENT, `id2` int(11) NOT NULL, KEY `t1_id_fk` (`id`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t2 add index id_test (id), add index id_test2 (id,id2); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `id` int(11) NOT NULL AUTO_INCREMENT, `id2` int(11) NOT NULL, KEY `id_test` (`id`), KEY `id_test2` (`id`,`id2`), CONSTRAINT `t1_id_fk` FOREIGN KEY (`id`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (id int(11) not null, id2 int(11) not null, constraint t1_id_fk foreign key (id2,id) references t1 (id)) engine = innodb; ERROR 42000: Incorrect foreign key definition for 't1_id_fk': Key reference and table reference don't match create table t2 (a int auto_increment primary key, b int, index(b), foreign key (b) references t1(id), unique(b)) engine=innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `a` int(11) NOT NULL AUTO_INCREMENT, `b` int(11) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `b_2` (`b`), KEY `b` (`b`), CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`b`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2; create table t2 (a int auto_increment primary key, b int, foreign key (b) references t1(id), foreign key (b) references t1(id), unique(b)) engine=innodb; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `a` int(11) NOT NULL AUTO_INCREMENT, `b` int(11) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `b` (`b`), CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`b`) REFERENCES `t1` (`id`), CONSTRAINT `t2_ibfk_2` FOREIGN KEY (`b`) REFERENCES `t1` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t2, t1; create table t1 (c char(10), index (c,c)) engine=innodb; ERROR 42S21: Duplicate column name 'c' create table t1 (c1 char(10), c2 char(10), index (c1,c2,c1)) engine=innodb; ERROR 42S21: Duplicate column name 'c1' create table t1 (c1 char(10), c2 char(10), index (c1,c1,c2)) engine=innodb; ERROR 42S21: Duplicate column name 'c1' create table t1 (c1 char(10), c2 char(10), index (c2,c1,c1)) engine=innodb; ERROR 42S21: Duplicate column name 'c1' create table t1 (c1 char(10), c2 char(10)) engine=innodb; alter table t1 add key (c1,c1); ERROR 42S21: Duplicate column name 'c1' alter table t1 add key (c2,c1,c1); ERROR 42S21: Duplicate column name 'c1' alter table t1 add key (c1,c2,c1); ERROR 42S21: Duplicate column name 'c1' alter table t1 add key (c1,c1,c2); ERROR 42S21: Duplicate column name 'c1' drop table t1; create table t1(a int(1) , b int(1)) engine=innodb; insert into t1 values ('1111', '3333'); select distinct concat(a, b) from t1; concat(a, b) 11113333 drop table t1; CREATE TABLE t1 ( a char(10) ) ENGINE=InnoDB; SELECT a FROM t1 WHERE MATCH (a) AGAINST ('test' IN BOOLEAN MODE); ERROR HY000: The used table type doesn't support FULLTEXT indexes DROP TABLE t1; CREATE TABLE t1 (a_id tinyint(4) NOT NULL default '0', PRIMARY KEY (a_id)) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO t1 VALUES (1),(2),(3); CREATE TABLE t2 (b_id tinyint(4) NOT NULL default '0',b_a tinyint(4) NOT NULL default '0', PRIMARY KEY (b_id), KEY (b_a), CONSTRAINT fk_b_a FOREIGN KEY (b_a) REFERENCES t1 (a_id) ON DELETE CASCADE ON UPDATE NO ACTION) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO t2 VALUES (1,1),(2,1),(3,1),(4,2),(5,2); SELECT * FROM (SELECT t1.*,GROUP_CONCAT(t2.b_id SEPARATOR ',') as b_list FROM (t1 LEFT JOIN (t2) on t1.a_id = t2.b_a) GROUP BY t1.a_id ) AS xyz; a_id b_list 1 1,2,3 2 4,5 3 NULL DROP TABLE t2; DROP TABLE t1; create temporary table t1 (a int) engine=innodb; insert into t1 values (4711); truncate t1; insert into t1 values (42); select * from t1; a 42 drop table t1; create table t1 (a int) engine=innodb; insert into t1 values (4711); truncate t1; insert into t1 values (42); select * from t1; a 42 drop table t1; create table t1 (a int not null, b int not null, c blob not null, d int not null, e int, primary key (a,b,c(255),d)) engine=innodb; insert into t1 values (2,2,"b",2,2),(1,1,"a",1,1),(3,3,"ab",3,3); select * from t1 order by a,b,c,d; a b c d e 1 1 a 1 1 2 2 b 2 2 3 3 ab 3 3 explain select * from t1 order by a,b,c,d; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using filesort drop table t1; create table t1 (a char(1), b char(1), key(a, b)) engine=innodb; insert into t1 values ('8', '6'), ('4', '7'); select min(a) from t1; min(a) 4 select min(b) from t1 where a='8'; min(b) 6 drop table t1; create table t1 (x bigint unsigned not null primary key) engine=innodb; insert into t1(x) values (0xfffffffffffffff0),(0xfffffffffffffff1); select * from t1; x 18446744073709551600 18446744073709551601 select count(*) from t1 where x>0; count(*) 2 select count(*) from t1 where x=0; count(*) 0 select count(*) from t1 where x<0; count(*) 0 select count(*) from t1 where x < -16; count(*) 0 select count(*) from t1 where x = -16; count(*) 0 explain select count(*) from t1 where x > -16; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index PRIMARY PRIMARY 8 NULL 2 Using where; Using index select count(*) from t1 where x > -16; count(*) 2 select * from t1 where x > -16; x 18446744073709551600 18446744073709551601 select count(*) from t1 where x = 18446744073709551601; count(*) 1 drop table t1; SELECT variable_value FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_buffer_pool_pages_total'; variable_value 512 SELECT variable_value FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_page_size'; variable_value 16384 SELECT variable_value - @innodb_rows_deleted_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_rows_deleted'; variable_value - @innodb_rows_deleted_orig 71 SELECT variable_value - @innodb_rows_inserted_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_rows_inserted'; variable_value - @innodb_rows_inserted_orig 1063 SELECT variable_value - @innodb_rows_updated_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_rows_updated'; variable_value - @innodb_rows_updated_orig 865 SELECT variable_value - @innodb_row_lock_waits_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_row_lock_waits'; variable_value - @innodb_row_lock_waits_orig 0 SELECT variable_value - @innodb_row_lock_current_waits_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_row_lock_current_waits'; variable_value - @innodb_row_lock_current_waits_orig 0 SELECT variable_value - @innodb_row_lock_time_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_row_lock_time'; variable_value - @innodb_row_lock_time_orig 0 SELECT variable_value - @innodb_row_lock_time_max_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_row_lock_time_max'; variable_value - @innodb_row_lock_time_max_orig 0 SELECT variable_value - @innodb_row_lock_time_avg_orig FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_row_lock_time_avg'; variable_value - @innodb_row_lock_time_avg_orig 0 show variables like "innodb_sync_spin_loops"; Variable_name Value innodb_sync_spin_loops 20 set global innodb_sync_spin_loops=1000; show variables like "innodb_sync_spin_loops"; Variable_name Value innodb_sync_spin_loops 1000 set global innodb_sync_spin_loops=0; show variables like "innodb_sync_spin_loops"; Variable_name Value innodb_sync_spin_loops 0 set global innodb_sync_spin_loops=20; show variables like "innodb_sync_spin_loops"; Variable_name Value innodb_sync_spin_loops 20 SET @old_innodb_thread_concurrency= @@global.innodb_thread_concurrency; show variables like "innodb_thread_concurrency"; Variable_name Value innodb_thread_concurrency 8 set global innodb_thread_concurrency=1001; Warnings: Warning 1292 Truncated incorrect thread_concurrency value: '1001' show variables like "innodb_thread_concurrency"; Variable_name Value innodb_thread_concurrency 1000 set global innodb_thread_concurrency=0; show variables like "innodb_thread_concurrency"; Variable_name Value innodb_thread_concurrency 0 set global innodb_thread_concurrency=16; show variables like "innodb_thread_concurrency"; Variable_name Value innodb_thread_concurrency 16 SET @@global.innodb_thread_concurrency= @old_innodb_thread_concurrency; show variables like "innodb_concurrency_tickets"; Variable_name Value innodb_concurrency_tickets 500 set global innodb_concurrency_tickets=1000; show variables like "innodb_concurrency_tickets"; Variable_name Value innodb_concurrency_tickets 1000 set global innodb_concurrency_tickets=0; Warnings: Warning 1292 Truncated incorrect concurrency_tickets value: '0' show variables like "innodb_concurrency_tickets"; Variable_name Value innodb_concurrency_tickets 1 set global innodb_concurrency_tickets=500; show variables like "innodb_concurrency_tickets"; Variable_name Value innodb_concurrency_tickets 500 show variables like "innodb_thread_sleep_delay"; Variable_name Value innodb_thread_sleep_delay 10000 set global innodb_thread_sleep_delay=100000; show variables like "innodb_thread_sleep_delay"; Variable_name Value innodb_thread_sleep_delay 100000 set global innodb_thread_sleep_delay=0; show variables like "innodb_thread_sleep_delay"; Variable_name Value innodb_thread_sleep_delay 0 set global innodb_thread_sleep_delay=10000; show variables like "innodb_thread_sleep_delay"; Variable_name Value innodb_thread_sleep_delay 10000 set storage_engine=INNODB; drop table if exists t1,t2,t3; --- Testing varchar --- --- Testing varchar --- create table t1 (v varchar(10), c char(10), t text); insert into t1 values('+ ', '+ ', '+ '); set @a=repeat(' ',20); insert into t1 values (concat('+',@a),concat('+',@a),concat('+',@a)); Warnings: Note 1265 Data truncated for column 'v' at row 1 select concat('*',v,'*',c,'*',t,'*') from t1; concat('*',v,'*',c,'*',t,'*') *+ *+*+ * *+ *+*+ * show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text ) ENGINE=InnoDB DEFAULT CHARSET=latin1 create table t2 like t1; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text ) ENGINE=InnoDB DEFAULT CHARSET=latin1 create table t3 select * from t1; show create table t3; Table Create Table t3 CREATE TABLE `t3` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 modify c varchar(10); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` varchar(10) DEFAULT NULL, `t` text ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 modify v char(10); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` char(10) DEFAULT NULL, `c` varchar(10) DEFAULT NULL, `t` text ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 modify t varchar(10); Warnings: Note 1265 Data truncated for column 't' at row 2 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` char(10) DEFAULT NULL, `c` varchar(10) DEFAULT NULL, `t` varchar(10) DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1 select concat('*',v,'*',c,'*',t,'*') from t1; concat('*',v,'*',c,'*',t,'*') *+*+*+ * *+*+*+ * drop table t1,t2,t3; create table t1 (v varchar(10), c char(10), t text, key(v), key(c), key(t(10))); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text, KEY `v` (`v`), KEY `c` (`c`), KEY `t` (`t`(10)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 select count(*) from t1; count(*) 270 insert into t1 values(concat('a',char(1)),concat('a',char(1)),concat('a',char(1))); select count(*) from t1 where v='a'; count(*) 10 select count(*) from t1 where c='a'; count(*) 10 select count(*) from t1 where t='a'; count(*) 10 select count(*) from t1 where v='a '; count(*) 10 select count(*) from t1 where c='a '; count(*) 10 select count(*) from t1 where t='a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; count(*) 10 select count(*) from t1 where v like 'a%'; count(*) 11 select count(*) from t1 where c like 'a%'; count(*) 11 select count(*) from t1 where t like 'a%'; count(*) 11 select count(*) from t1 where v like 'a %'; count(*) 9 explain select count(*) from t1 where v='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const # Using where; Using index explain select count(*) from t1 where c='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref c c 11 const # Using where; Using index explain select count(*) from t1 where t='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref t t 13 const # Using where explain select count(*) from t1 where v like 'a%'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range v v 13 NULL # Using where; Using index explain select count(*) from t1 where v between 'a' and 'a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const # Using where; Using index explain select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const # Using where; Using index alter table t1 add unique(v); ERROR 23000: Duplicate entry '{ ' for key 'v_2' alter table t1 add key(v); select concat('*',v,'*',c,'*',t,'*') as qq from t1 where v='a'; qq *a*a*a* *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * explain select * from t1 where v='a'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v,v_2 # 13 const # Using where select v,count(*) from t1 group by v limit 10; v count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select v,count(c) from t1 group by v limit 10; v count(c) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result v,count(c) from t1 group by v limit 10; v count(c) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select c,count(*) from t1 group by c limit 10; c count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select c,count(t) from t1 group by c limit 10; c count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result c,count(t) from t1 group by c limit 10; c count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select t,count(*) from t1 group by t limit 10; t count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select t,count(t) from t1 group by t limit 10; t count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result t,count(t) from t1 group by t limit 10; t count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 alter table t1 modify v varchar(300), drop key v, drop key v_2, add key v (v); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(300) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text, KEY `c` (`c`), KEY `t` (`t`(10)), KEY `v` (`v`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 select count(*) from t1 where v='a'; count(*) 10 select count(*) from t1 where v='a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; count(*) 10 select count(*) from t1 where v like 'a%'; count(*) 11 select count(*) from t1 where v like 'a %'; count(*) 9 explain select count(*) from t1 where v='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 303 const # Using where; Using index explain select count(*) from t1 where v like 'a%'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range v v 303 NULL # Using where; Using index explain select count(*) from t1 where v between 'a' and 'a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 303 const # Using where; Using index explain select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 303 const # Using where; Using index explain select * from t1 where v='a'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 303 const # Using where select v,count(*) from t1 group by v limit 10; v count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 alter table t1 drop key v, add key v (v(30)); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(300) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text, KEY `c` (`c`), KEY `t` (`t`(10)), KEY `v` (`v`(30)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 select count(*) from t1 where v='a'; count(*) 10 select count(*) from t1 where v='a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; count(*) 10 select count(*) from t1 where v like 'a%'; count(*) 11 select count(*) from t1 where v like 'a %'; count(*) 9 explain select count(*) from t1 where v='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 33 const # Using where explain select count(*) from t1 where v like 'a%'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range v v 33 NULL # Using where explain select count(*) from t1 where v between 'a' and 'a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 33 const # Using where explain select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 33 const # Using where explain select * from t1 where v='a'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 33 const # Using where select v,count(*) from t1 group by v limit 10; v count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 alter table t1 modify v varchar(600), drop key v, add key v (v); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(600) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text, KEY `c` (`c`), KEY `t` (`t`(10)), KEY `v` (`v`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 select v,count(*) from t1 group by v limit 10; v count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 drop table t1; create table t1 (a char(10), unique (a)); insert into t1 values ('a '); insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a' for key 'a' alter table t1 modify a varchar(10); insert into t1 values ('a '),('a '),('a '),('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' update t1 set a='a ' where a like 'a%'; select concat(a,'.') from t1; concat(a,'.') a . update t1 set a='abc ' where a like 'a '; select concat(a,'.') from t1; concat(a,'.') a . update t1 set a='a ' where a like 'a %'; select concat(a,'.') from t1; concat(a,'.') a . update t1 set a='a ' where a like 'a '; select concat(a,'.') from t1; concat(a,'.') a . drop table t1; create table t1 (v varchar(10), c char(10), t text, key(v(5)), key(c(5)), key(t(5))); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` text, KEY `v` (`v`(5)), KEY `c` (`c`(5)), KEY `t` (`t`(5)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1 (v char(10) character set utf8); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` char(10) CHARACTER SET utf8 DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1 (v varchar(10), c char(10)) row_format=fixed; show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=FIXED insert into t1 values('a','a'),('a ','a '); select concat('*',v,'*',c,'*') from t1; concat('*',v,'*',c,'*') *a*a* *a *a* drop table t1; create table t1 (v varchar(65530), key(v(10))); insert into t1 values(repeat('a',65530)); select length(v) from t1 where v=repeat('a',65530); length(v) 65530 drop table t1; create table t1(a int, b varchar(12), key ba(b, a)); insert into t1 values (1, 'A'), (20, NULL); explain select * from t1 where a=20 and b is null; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref ba ba 20 const,const 1 Using where; Using index select * from t1 where a=20 and b is null; a b 20 NULL drop table t1; create table t1 (v varchar(65530), key(v)); Warnings: Warning 1071 Specified key was too long; max key length is 767 bytes drop table t1; create table t1 (v varchar(65536)); Warnings: Note 1246 Converting column 'v' from VARCHAR to TEXT show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` mediumtext ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1 (v varchar(65530) character set utf8); Warnings: Note 1246 Converting column 'v' from VARCHAR to TEXT show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` mediumtext CHARACTER SET utf8 ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; set storage_engine=MyISAM;