create table t1(a int not null, b int, c char(10) not null, d varchar(20)) engine = innodb; insert into t1 values (5,5,'oo','oo'),(4,4,'tr','tr'),(3,4,'ad','ad'),(2,3,'ak','ak'); commit; alter table t1 add index b (b), add index b (b); ERROR 42000: Duplicate key name 'b' alter table t1 add index (b,b); ERROR 42S21: Duplicate column name 'b' alter table t1 add index d2 (d); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, KEY `d2` (`d`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 explain select * from t1 force index(d2) order by d; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL d2 23 NULL 4 select * from t1 force index (d2) order by d; a b c d 3 4 ad ad 2 3 ak ak 5 5 oo oo 4 4 tr tr alter table t1 add unique index (b); ERROR 23000: Duplicate entry '4' for key 'b' show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, KEY `d2` (`d`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 add index (b); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, KEY `d2` (`d`), KEY `b` (`b`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CREATE TABLE `t1#1`(a INT PRIMARY KEY) ENGINE=InnoDB; call mtr.add_suppression(" table `test`\\.`t1#[12]` already exists in InnoDB internal"); alter table t1 add unique index (c), add index (d); ERROR HY000: Table 'test.t1#1' already exists rename table `t1#1` to `t1#2`; alter table t1 add unique index (c), add index (d); ERROR HY000: Table 'test.t1#2' already exists drop table `t1#2`; alter table t1 add unique index (c), add index (d); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, UNIQUE KEY `c` (`c`), KEY `d2` (`d`), KEY `b` (`b`), KEY `d` (`d`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL c 10 NULL 4 alter table t1 add primary key (a), drop index c; show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), KEY `d2` (`d`), KEY `b` (`b`), KEY `d` (`d`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 add primary key (c); ERROR 42000: Multiple primary key defined alter table t1 drop primary key, add primary key (b); ERROR 23000: Duplicate entry '4' for key 'PRIMARY' create unique index c on t1 (c); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `c` (`c`), KEY `d2` (`d`), KEY `b` (`b`), KEY `d` (`d`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL c 10 NULL 4 select * from t1 force index(c) order by c; a b c d 3 4 ad ad 2 3 ak ak 5 5 oo oo 4 4 tr tr alter table t1 drop index b, add index (b); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `c` (`c`), KEY `d2` (`d`), KEY `d` (`d`), KEY `b` (`b`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 insert into t1 values(6,1,'ggg','ggg'); select * from t1; a b c d 2 3 ak ak 3 4 ad ad 4 4 tr tr 5 5 oo oo 6 1 ggg ggg select * from t1 force index(b) order by b; a b c d 6 1 ggg ggg 2 3 ak ak 3 4 ad ad 4 4 tr tr 5 5 oo oo select * from t1 force index(c) order by c; a b c d 3 4 ad ad 2 3 ak ak 6 1 ggg ggg 5 5 oo oo 4 4 tr tr select * from t1 force index(d) order by d; a b c d 3 4 ad ad 2 3 ak ak 6 1 ggg ggg 5 5 oo oo 4 4 tr tr explain select * from t1 force index(b) order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 5 NULL 5 explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL c 10 NULL 5 explain select * from t1 force index(d) order by d; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL d 23 NULL 5 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) NOT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `c` (`c`), KEY `d2` (`d`), KEY `d` (`d`), KEY `b` (`b`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1(a int not null, b int, c char(10), d varchar(20), primary key (a)) engine = innodb; insert into t1 values (1,1,'ab','ab'),(2,2,'ac','ac'),(3,3,'ad','ad'),(4,4,'afe','afe'); commit; alter table t1 add index (c(2)); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), KEY `c` (`c`(2)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 add unique index (d(10)); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `d` (`d`(10)), KEY `c` (`c`(2)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 insert into t1 values(5,1,'ggg','ggg'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 3 ad ad 4 4 afe afe 5 1 ggg ggg select * from t1 force index(c) order by c; a b c d 1 1 ab ab 2 2 ac ac 3 3 ad ad 4 4 afe afe 5 1 ggg ggg select * from t1 force index(d) order by d; a b c d 1 1 ab ab 2 2 ac ac 3 3 ad ad 4 4 afe afe 5 1 ggg ggg 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 5 Using filesort explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 5 Using filesort explain select * from t1 force index(d) order by d; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 5 Using filesort show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `d` (`d`(10)), KEY `c` (`c`(2)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 drop index d; insert into t1 values(8,9,'fff','fff'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 3 ad ad 4 4 afe afe 5 1 ggg ggg 8 9 fff fff select * from t1 force index(c) order by c; a b c d 1 1 ab ab 2 2 ac ac 3 3 ad ad 4 4 afe afe 8 9 fff fff 5 1 ggg ggg 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 6 Using filesort explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 6 Using filesort explain select * from t1 order by d; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 6 Using filesort show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), KEY `c` (`c`(2)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1(a int not null, b int, c char(10), d varchar(20), primary key (a)) engine = innodb; insert into t1 values (1,1,'ab','ab'),(2,2,'ac','ac'),(3,2,'ad','ad'),(4,4,'afe','afe'); commit; alter table t1 add unique index (b,c); insert into t1 values(8,9,'fff','fff'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff select * from t1 force index(b) order by b; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff explain select * from t1 force index(b) order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 16 NULL 5 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `b` (`b`,`c`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 add index (b,c); insert into t1 values(11,11,'kkk','kkk'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 11 11 kkk kkk select * from t1 force index(b) order by b; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 11 11 kkk kkk explain select * from t1 force index(b) order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 16 NULL 6 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `b` (`b`,`c`), KEY `b_2` (`b`,`c`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t1 add unique index (c,d); insert into t1 values(13,13,'yyy','aaa'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 11 11 kkk kkk 13 13 yyy aaa select * from t1 force index(b) order by b; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 11 11 kkk kkk 13 13 yyy aaa select * from t1 force index(c) order by c; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 11 11 kkk kkk 13 13 yyy aaa explain select * from t1 force index(b) order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 16 NULL 7 explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL c 34 NULL 7 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `b` (`b`,`c`), UNIQUE KEY `c` (`c`,`d`), KEY `b_2` (`b`,`c`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1(a int not null, b int not null, c int, primary key (a), key (b)) engine = innodb; create table t3(a int not null, c int not null, d int, primary key (a), key (c)) engine = innodb; create table t4(a int not null, d int not null, e int, primary key (a), key (d)) engine = innodb; create table t2(a int not null, b int not null, c int not null, d int not null, e int, foreign key (b) references t1(b) on delete cascade, foreign key (c) references t3(c), foreign key (d) references t4(d)) engine = innodb; alter table t1 drop index b; ERROR HY000: Cannot drop index 'b': needed in a foreign key constraint alter table t3 drop index c; ERROR HY000: Cannot drop index 'c': needed in a foreign key constraint alter table t4 drop index d; ERROR HY000: Cannot drop index 'd': needed in a foreign key constraint alter table t2 drop index b; ERROR HY000: Cannot drop index 'b': needed in a foreign key constraint alter table t2 drop index b, drop index c, drop index d; ERROR HY000: Cannot drop index 'b': needed in a foreign key constraint create unique index dc on t2 (d,c); create index dc on t1 (b,c); alter table t2 add primary key (a); insert into t1 values (1,1,1); insert into t3 values (1,1,1); insert into t4 values (1,1,1); insert into t2 values (1,1,1,1,1); commit; alter table t4 add constraint dc foreign key (a) references t1(a); show create table t4; Table Create Table t4 CREATE TABLE `t4` ( `a` int(11) NOT NULL, `d` int(11) NOT NULL, `e` int(11) DEFAULT NULL, PRIMARY KEY (`a`), KEY `d` (`d`), CONSTRAINT `dc` FOREIGN KEY (`a`) REFERENCES `t1` (`a`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t3 add constraint dc foreign key (a) references t1(a); ERROR HY000: Can't create table '#sql-temporary' (errno: 121) show create table t3; Table Create Table t3 CREATE TABLE `t3` ( `a` int(11) NOT NULL, `c` int(11) NOT NULL, `d` int(11) DEFAULT NULL, PRIMARY KEY (`a`), KEY `c` (`c`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 alter table t2 drop index b, add index (b); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `a` int(11) NOT NULL, `b` int(11) NOT NULL, `c` int(11) NOT NULL, `d` int(11) NOT NULL, `e` int(11) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `dc` (`d`,`c`), KEY `c` (`c`), KEY `b` (`b`), CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`b`) REFERENCES `t1` (`b`) ON DELETE CASCADE, CONSTRAINT `t2_ibfk_2` FOREIGN KEY (`c`) REFERENCES `t3` (`c`), CONSTRAINT `t2_ibfk_3` FOREIGN KEY (`d`) REFERENCES `t4` (`d`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 delete from t1; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t4`, CONSTRAINT `dc` FOREIGN KEY (`a`) REFERENCES `t1` (`a`)) drop index dc on t4; ERROR 42000: Can't DROP 'dc'; check that column/key exists alter table t3 drop foreign key dc; ERROR HY000: Error on rename of './test/t3' to './#sql2-temporary' (errno: 152) alter table t4 drop foreign key dc; select * from t2; a b c d e 1 1 1 1 1 delete from t1; select * from t2; a b c d e drop table t2,t4,t3,t1; create table t1(a int not null, b int, c char(10), d varchar(20), primary key (a)) engine = innodb default charset=utf8; insert into t1 values (1,1,'ab','ab'),(2,2,'ac','ac'),(3,2,'ad','ad'),(4,4,'afe','afe'); commit; alter table t1 add unique index (b); ERROR 23000: Duplicate entry '2' for key 'b' insert into t1 values(8,9,'fff','fff'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 alter table t1 add index (b); insert into t1 values(10,10,'kkk','iii'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 10 10 kkk iii select * from t1 force index(b) order by b; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 10 10 kkk iii explain select * from t1 force index(b) order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 5 NULL 6 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), KEY `b` (`b`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 alter table t1 add unique index (c), add index (d); insert into t1 values(11,11,'aaa','mmm'); select * from t1; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 10 10 kkk iii 11 11 aaa mmm select * from t1 force index(b) order by b; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 10 10 kkk iii 11 11 aaa mmm select * from t1 force index(c) order by c; a b c d 11 11 aaa mmm 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 10 10 kkk iii select * from t1 force index(d) order by d; a b c d 1 1 ab ab 2 2 ac ac 3 2 ad ad 4 4 afe afe 8 9 fff fff 10 10 kkk iii 11 11 aaa mmm explain select * from t1 force index(b) order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 5 NULL 7 explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL c 31 NULL 7 explain select * from t1 force index(d) order by d; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL d 63 NULL 7 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `c` (`c`), KEY `b` (`b`), KEY `d` (`d`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 check table t1; Table Op Msg_type Msg_text test.t1 check status OK drop table t1; create table t1(a int not null, b int) engine = innodb; insert into t1 values (1,1),(1,1),(1,1),(1,1); alter table t1 add unique index (a); ERROR 23000: Duplicate entry '1' for key 'a' alter table t1 add unique index (b); ERROR 23000: Duplicate entry '1' for key 'b' alter table t1 add unique index (a), add unique index(b); ERROR 23000: Duplicate entry '1' for key 'a' show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1(a int not null, c int not null,b int, primary key(a), unique key(c), key(b)) engine = innodb; alter table t1 drop index c, drop index b; show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `c` int(11) NOT NULL, `b` int(11) DEFAULT NULL, PRIMARY KEY (`a`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1(a int not null, b int, primary key(a)) engine = innodb; alter table t1 add index (b); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, PRIMARY KEY (`a`), KEY `b` (`b`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1(a int not null, b int, c char(10), d varchar(20), primary key (a)) engine = innodb; insert into t1 values (1,1,'ab','ab'),(2,2,'ac','ac'),(3,3,'ac','ac'),(4,4,'afe','afe'),(5,4,'affe','affe'); alter table t1 add unique index (b), add unique index (c), add unique index (d); ERROR 23000: Duplicate entry 'ac' for key 'c' alter table t1 add unique index (c), add unique index (b), add index (d); ERROR 23000: Duplicate entry 'ac' for key 'c' show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` char(10) DEFAULT NULL, `d` varchar(20) DEFAULT NULL, PRIMARY KEY (`a`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 drop table t1; create table t1(a int not null, b int not null, c int, primary key (a), key(c)) engine=innodb; insert into t1 values (5,1,5),(4,2,4),(3,3,3),(2,4,2),(1,5,1); alter table t1 add unique index (b); insert into t1 values (10,20,20),(11,19,19),(12,18,18),(13,17,17); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) NOT NULL, `c` int(11) DEFAULT NULL, PRIMARY KEY (`a`), UNIQUE KEY `b` (`b`), KEY `c` (`c`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 check table t1; Table Op Msg_type Msg_text test.t1 check status OK explain select * from t1 force index(c) order by c; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL c 5 NULL 9 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 9 explain select * from t1 force index(b) order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL b 4 NULL 9 select * from t1 order by a; a b c 1 5 1 2 4 2 3 3 3 4 2 4 5 1 5 10 20 20 11 19 19 12 18 18 13 17 17 select * from t1 force index(b) order by b; a b c 5 1 5 4 2 4 3 3 3 2 4 2 1 5 1 13 17 17 12 18 18 11 19 19 10 20 20 select * from t1 force index(c) order by c; a b c 1 5 1 2 4 2 3 3 3 4 2 4 5 1 5 13 17 17 12 18 18 11 19 19 10 20 20 drop table t1; create table t1(a int not null, b int not null) engine=innodb; insert into t1 values (1,1); alter table t1 add primary key(b); insert into t1 values (2,2); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, `b` int(11) NOT NULL, PRIMARY KEY (`b`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 check table t1; Table Op Msg_type Msg_text test.t1 check status OK select * from t1; a b 1 1 2 2 explain select * from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 2 explain select * from t1 order by a; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL NULL NULL NULL NULL 2 Using filesort explain select * from t1 order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL PRIMARY 4 NULL 2 checksum table t1; Table Checksum test.t1 582702641 drop table t1; create table t1(a int not null) engine=innodb; insert into t1 values (1); alter table t1 add primary key(a); insert into t1 values (2); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, PRIMARY KEY (`a`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 check table t1; Table Op Msg_type Msg_text test.t1 check status OK commit; select * from t1; a 1 2 explain select * from t1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL PRIMARY 4 NULL 2 Using index 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 2 Using index drop table t1; create table t2(d varchar(17) primary key) engine=innodb default charset=utf8; create table t3(a int primary key) engine=innodb; insert into t3 values(22),(44),(33),(55),(66); insert into t2 values ('jejdkrun87'),('adfd72nh9k'), ('adfdpplkeock'),('adfdijnmnb78k'),('adfdijn0loKNHJik'); create table t1(a int, b blob, c text, d text not null) engine=innodb default charset = utf8; insert into t1 select a,left(repeat(d,100*a),65535),repeat(d,20*a),d from t2,t3; drop table t2, t3; select count(*) from t1 where a=44; count(*) 5 select a, length(b),b=left(repeat(d,100*a),65535),length(c),c=repeat(d,20*a),d from t1; a length(b) b=left(repeat(d,100*a),65535) length(c) c=repeat(d,20*a) d 22 22000 1 4400 1 adfd72nh9k 22 35200 1 7040 1 adfdijn0loKNHJik 22 28600 1 5720 1 adfdijnmnb78k 22 26400 1 5280 1 adfdpplkeock 22 22000 1 4400 1 jejdkrun87 33 33000 1 6600 1 adfd72nh9k 33 52800 1 10560 1 adfdijn0loKNHJik 33 42900 1 8580 1 adfdijnmnb78k 33 39600 1 7920 1 adfdpplkeock 33 33000 1 6600 1 jejdkrun87 44 44000 1 8800 1 adfd72nh9k 44 65535 1 14080 1 adfdijn0loKNHJik 44 57200 1 11440 1 adfdijnmnb78k 44 52800 1 10560 1 adfdpplkeock 44 44000 1 8800 1 jejdkrun87 55 55000 1 11000 1 adfd72nh9k 55 65535 1 17600 1 adfdijn0loKNHJik 55 65535 1 14300 1 adfdijnmnb78k 55 65535 1 13200 1 adfdpplkeock 55 55000 1 11000 1 jejdkrun87 66 65535 1 13200 1 adfd72nh9k 66 65535 1 21120 1 adfdijn0loKNHJik 66 65535 1 17160 1 adfdijnmnb78k 66 65535 1 15840 1 adfdpplkeock 66 65535 1 13200 1 jejdkrun87 alter table t1 add primary key (a), add key (b(20)); ERROR 23000: Duplicate entry '22' for key 'PRIMARY' delete from t1 where a%2; check table t1; Table Op Msg_type Msg_text test.t1 check status OK alter table t1 add primary key (a,b(255),c(255)), add key (b(767)); select count(*) from t1 where a=44; count(*) 5 select a, length(b),b=left(repeat(d,100*a),65535),length(c),c=repeat(d,20*a),d from t1; a length(b) b=left(repeat(d,100*a),65535) length(c) c=repeat(d,20*a) d 22 22000 1 4400 1 adfd72nh9k 22 35200 1 7040 1 adfdijn0loKNHJik 22 28600 1 5720 1 adfdijnmnb78k 22 26400 1 5280 1 adfdpplkeock 22 22000 1 4400 1 jejdkrun87 44 44000 1 8800 1 adfd72nh9k 44 65535 1 14080 1 adfdijn0loKNHJik 44 57200 1 11440 1 adfdijnmnb78k 44 52800 1 10560 1 adfdpplkeock 44 44000 1 8800 1 jejdkrun87 66 65535 1 13200 1 adfd72nh9k 66 65535 1 21120 1 adfdijn0loKNHJik 66 65535 1 17160 1 adfdijnmnb78k 66 65535 1 15840 1 adfdpplkeock 66 65535 1 13200 1 jejdkrun87 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL DEFAULT '0', `b` blob NOT NULL, `c` text NOT NULL, `d` text NOT NULL, PRIMARY KEY (`a`,`b`(255),`c`(255)), KEY `b` (`b`(767)) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 check table t1; Table Op Msg_type Msg_text test.t1 check status OK explain select * from t1 where b like 'adfd%'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL b NULL NULL NULL 15 Using where create table t2(a int, b varchar(255), primary key(a,b)) engine=innodb; insert into t2 select a,left(b,255) from t1; drop table t1; rename table t2 to t1; set innodb_lock_wait_timeout=1; begin; select a from t1 limit 1 for update; a 22 set innodb_lock_wait_timeout=1; create index t1ba on t1 (b,a); ERROR HY000: Lock wait timeout exceeded; try restarting transaction commit; begin; select a from t1 limit 1 lock in share mode; a 22 create index t1ba on t1 (b,a); drop index t1ba on t1; ERROR HY000: Lock wait timeout exceeded; try restarting transaction commit; explain select a from t1 order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL t1ba 261 NULL 15 Using index select a,sleep(2+a/100) from t1 order by b limit 3; select sleep(1); sleep(1) 0 drop index t1ba on t1; a sleep(2+a/100) 22 0 44 0 66 0 explain select a from t1 order by b; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL PRIMARY 261 NULL 15 Using index; Using filesort select a from t1 order by b limit 3; a 22 66 44 commit; drop table t1; set global innodb_file_per_table=on; set global innodb_file_format='Barracuda'; create table t1(a blob,b blob,c blob,d blob,e blob,f blob,g blob,h blob, i blob,j blob,k blob,l blob,m blob,n blob,o blob,p blob, q blob,r blob,s blob,t blob,u blob) engine=innodb row_format=dynamic; create index t1a on t1 (a(1)); create index t1b on t1 (b(1)); create index t1c on t1 (c(1)); create index t1d on t1 (d(1)); create index t1e on t1 (e(1)); create index t1f on t1 (f(1)); create index t1g on t1 (g(1)); create index t1h on t1 (h(1)); create index t1i on t1 (i(1)); create index t1j on t1 (j(1)); create index t1k on t1 (k(1)); create index t1l on t1 (l(1)); create index t1m on t1 (m(1)); create index t1n on t1 (n(1)); create index t1o on t1 (o(1)); create index t1p on t1 (p(1)); create index t1q on t1 (q(1)); create index t1r on t1 (r(1)); create index t1s on t1 (s(1)); create index t1t on t1 (t(1)); create index t1u on t1 (u(1)); ERROR HY000: Too big row create index t1ut on t1 (u(1), t(1)); ERROR HY000: Too big row create index t1st on t1 (s(1), t(1)); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` blob, `b` blob, `c` blob, `d` blob, `e` blob, `f` blob, `g` blob, `h` blob, `i` blob, `j` blob, `k` blob, `l` blob, `m` blob, `n` blob, `o` blob, `p` blob, `q` blob, `r` blob, `s` blob, `t` blob, `u` blob, KEY `t1a` (`a`(1)), KEY `t1b` (`b`(1)), KEY `t1c` (`c`(1)), KEY `t1d` (`d`(1)), KEY `t1e` (`e`(1)), KEY `t1f` (`f`(1)), KEY `t1g` (`g`(1)), KEY `t1h` (`h`(1)), KEY `t1i` (`i`(1)), KEY `t1j` (`j`(1)), KEY `t1k` (`k`(1)), KEY `t1l` (`l`(1)), KEY `t1m` (`m`(1)), KEY `t1n` (`n`(1)), KEY `t1o` (`o`(1)), KEY `t1p` (`p`(1)), KEY `t1q` (`q`(1)), KEY `t1r` (`r`(1)), KEY `t1s` (`s`(1)), KEY `t1t` (`t`(1)), KEY `t1st` (`s`(1),`t`(1)) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=DYNAMIC create index t1u on t1 (u(1)); ERROR HY000: Too big row alter table t1 row_format=compact; create index t1u on t1 (u(1)); drop table t1; set global innodb_file_per_table=0; set global innodb_file_format=Antelope; set global innodb_file_format_check=Antelope; SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; CREATE TABLE t1( c1 BIGINT(12) NOT NULL, PRIMARY KEY (c1) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; CREATE TABLE t2( c1 BIGINT(16) NOT NULL, c2 BIGINT(12) NOT NULL, c3 BIGINT(12) NOT NULL, PRIMARY KEY (c1) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca FOREIGN KEY (c3) REFERENCES t1(c1); SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`), KEY `fk_t2_ca` (`c3`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CREATE INDEX i_t2_c3_c2 ON t2(c3, c2); SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`), KEY `i_t2_c3_c2` (`c3`,`c2`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; INSERT INTO t2 VALUES(0,0,0); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`)) INSERT INTO t1 VALUES(0); INSERT INTO t2 VALUES(0,0,0); DROP TABLE t2; CREATE TABLE t2( c1 BIGINT(16) NOT NULL, c2 BIGINT(12) NOT NULL, c3 BIGINT(12) NOT NULL, PRIMARY KEY (c1,c2,c3) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca FOREIGN KEY (c3) REFERENCES t1(c1); SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`,`c2`,`c3`), KEY `fk_t2_ca` (`c3`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CREATE INDEX i_t2_c3_c2 ON t2(c3, c2); SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`,`c2`,`c3`), KEY `i_t2_c3_c2` (`c3`,`c2`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 INSERT INTO t2 VALUES(0,0,1); ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`)) INSERT INTO t2 VALUES(0,0,0); DELETE FROM t1; ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`)) DELETE FROM t2; DROP TABLE t2; DROP TABLE t1; CREATE TABLE t1( c1 BIGINT(12) NOT NULL, c2 INT(4) NOT NULL, PRIMARY KEY (c2,c1) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; CREATE TABLE t2( c1 BIGINT(16) NOT NULL, c2 BIGINT(12) NOT NULL, c3 BIGINT(12) NOT NULL, PRIMARY KEY (c1) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca FOREIGN KEY (c3,c2) REFERENCES t1(c1,c1); ERROR HY000: Can't create table '#sql-temporary' (errno: 150) ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2); ERROR HY000: Can't create table '#sql-temporary' (errno: 150) ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1); ERROR HY000: Can't create table '#sql-temporary' (errno: 150) ALTER TABLE t1 MODIFY COLUMN c2 BIGINT(12) NOT NULL; ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2); ERROR HY000: Can't create table '#sql-temporary' (errno: 150) ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1); SHOW CREATE TABLE t1; Table Create Table t1 CREATE TABLE `t1` ( `c1` bigint(12) NOT NULL, `c2` bigint(12) NOT NULL, PRIMARY KEY (`c2`,`c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`), KEY `fk_t2_ca` (`c3`,`c2`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CREATE INDEX i_t2_c2_c1 ON t2(c2, c1); SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`), KEY `fk_t2_ca` (`c3`,`c2`), KEY `i_t2_c2_c1` (`c2`,`c1`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CREATE INDEX i_t2_c3_c1_c2 ON t2(c3, c1, c2); SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`), KEY `fk_t2_ca` (`c3`,`c2`), KEY `i_t2_c2_c1` (`c2`,`c1`), KEY `i_t2_c3_c1_c2` (`c3`,`c1`,`c2`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CREATE INDEX i_t2_c3_c2 ON t2(c3, c2); SHOW CREATE TABLE t2; Table Create Table t2 CREATE TABLE `t2` ( `c1` bigint(16) NOT NULL, `c2` bigint(12) NOT NULL, `c3` bigint(12) NOT NULL, PRIMARY KEY (`c1`), KEY `i_t2_c2_c1` (`c2`,`c1`), KEY `i_t2_c3_c1_c2` (`c3`,`c1`,`c2`), KEY `i_t2_c3_c2` (`c3`,`c2`), CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 DROP TABLE t2; DROP TABLE t1; call mtr.add_suppression("InnoDB: insufficient history for index"); CREATE TABLE t1 (a INT, b CHAR(1)) ENGINE=InnoDB; INSERT INTO t1 VALUES (3,'a'),(3,'b'),(1,'c'),(0,'d'),(1,'e'); BEGIN; SELECT * FROM t1; a b 3 a 3 b 1 c 0 d 1 e CREATE INDEX t1a ON t1(a); SELECT * FROM t1; a b 3 a 3 b 1 c 0 d 1 e SELECT * FROM t1 FORCE INDEX(t1a) ORDER BY a; ERROR HY000: Table definition has changed, please retry transaction SELECT * FROM t1; a b 3 a 3 b 1 c 0 d 1 e COMMIT; SELECT * FROM t1 FORCE INDEX(t1a) ORDER BY a; a b 0 d 1 c 1 e 3 a 3 b DROP TABLE t1;