set global innodb_file_per_table=on;
set global innodb_file_format='Barracuda';
SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS;
create table t1(a varchar(2) primary key) engine=innodb;
insert into t1 values('');
create index t1a1 on t1(a(1));
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
drop table t1;
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
alter table t1 add unique index (c), add index (d);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 1
Warnings:
Note	1831	Duplicate index 'd' defined on the table 'test.t1'. This is deprecated and will be disallowed in a future release.
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
analyze table t1;
Table	Op	Msg_type	Msg_text
test.t1	analyze	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	10	NULL	4	
alter table t1 add primary key (a), drop index c;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
affected rows: 1
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
Table	Op	Msg_type	Msg_text
test.t1	analyze	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	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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
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
analyze table t1;
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 `b` (`b`),
  KEY `d` (`d`)
) 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));
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
affected rows: 1
alter table t1 add unique index (d(10));
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
affected rows: 1
insert into t1 values(5,1,'ggg','ggg');
analyze table t1;
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;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
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, c int, d int, e int,
foreign key (b) references t1(b) on delete set null,
foreign key (c) references t3(c), foreign key (d) references t4(d) on update set null)
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
alter table t2 MODIFY b INT NOT NULL, ALGORITHM=COPY;
ERROR HY000: Cannot change column 'b': used in a foreign key constraint 't2_ibfk_1'
set @old_sql_mode = @@sql_mode;
set @@sql_mode = 'STRICT_TRANS_TABLES';
alter table t2 MODIFY b INT NOT NULL, ALGORITHM=INPLACE;
ERROR HY000: Column 'b' cannot be NOT NULL: needed in a foreign key constraint 'test/t2_ibfk_1' SET NULL
set @@sql_mode = @old_sql_mode;
SET FOREIGN_KEY_CHECKS=0;
alter table t2 DROP COLUMN b, ALGORITHM=COPY;
ERROR HY000: Cannot drop column 'b': needed in a foreign key constraint 't2_ibfk_1'
alter table t2 DROP COLUMN b;
ERROR HY000: Cannot drop column 'b': needed in a foreign key constraint 'test/t2_ibfk_1'
alter table t1 DROP COLUMN b, ALGORITHM=COPY;
ERROR HY000: Cannot drop column 'b': needed in a foreign key constraint 't2_ibfk_1' of table 'test.t2'
alter table t1 DROP COLUMN b;
ERROR HY000: Cannot drop column 'b': needed in a foreign key constraint 'test/t2_ibfk_1' of table '"test"."t2"'
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
create unique index dc on t2 (d,c);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
create index dc on t1 (b,c);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
set @@sql_mode = 'STRICT_TRANS_TABLES';
alter table t2 add primary key (alpha), change a alpha int,
change b beta int not null, change c charlie int not null;
ERROR HY000: Column 'b' cannot be NOT NULL: needed in a foreign key constraint 'test/t2_ibfk_1' SET NULL
alter table t2 add primary key (alpha), change a alpha int,
change c charlie int not null, change d delta int not null;
ERROR HY000: Column 'd' cannot be NOT NULL: needed in a foreign key constraint 'test/t2_ibfk_3' SET NULL
alter table t2 add primary key (alpha), change a alpha int,
change b beta int, modify c int not null;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
set @@sql_mode = @old_sql_mode;
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);
affected rows: 1
info: Records: 1  Duplicates: 0  Warnings: 0
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 `test`.`#sql-temporary` (errno: 121 "Duplicate key on write or update")
SET FOREIGN_KEY_CHECKS=0;
alter table t3 add constraint dc foreign key (a) references t1(a);
ERROR HY000: Failed to add the foreign key constraint 'test/dc' to system tables
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
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 (beta);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
show create table t2;
Table	Create Table
t2	CREATE TABLE `t2` (
  `alpha` int(11) NOT NULL DEFAULT '0',
  `beta` int(11) DEFAULT NULL,
  `c` int(11) NOT NULL,
  `d` int(11) DEFAULT NULL,
  `e` int(11) DEFAULT NULL,
  PRIMARY KEY (`alpha`),
  UNIQUE KEY `dc` (`d`,`c`),
  KEY `c` (`c`),
  KEY `beta` (`beta`),
  CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`beta`) REFERENCES `t1` (`b`) ON DELETE SET NULL,
  CONSTRAINT `t2_ibfk_2` FOREIGN KEY (`c`) REFERENCES `t3` (`c`),
  CONSTRAINT `t2_ibfk_3` FOREIGN KEY (`d`) REFERENCES `t4` (`d`) ON UPDATE SET NULL
) 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 42000: Can't DROP 'dc'; check that column/key exists
alter table t4 drop foreign key dc;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
select * from t2;
alpha	beta	c	d	e
1	1	1	1	1
delete from t1;
select * from t2;
alpha	beta	c	d	e
1	NULL	1	1	1
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 '4' for key 'b'
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
Table	Op	Msg_type	Msg_text
test.t1	analyze	status	OK
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);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
analyze table t1;
Table	Op	Msg_type	Msg_text
test.t1	analyze	status	OK
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;
set global innodb_file_per_table=1;
set global innodb_file_format=Antelope;
set global innodb_file_format_max=Antelope;
SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
SET 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;
SET FOREIGN_KEY_CHECKS=0;
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3) REFERENCES t1(c1);
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_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`,`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;
SET FOREIGN_KEY_CHECKS=0;
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c1,c1), ALGORITHM=COPY;
ERROR HY000: Can't create table `test`.`#sql-temporary` (errno: 150 "Foreign key constraint is incorrectly formed")
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c1,c1);
ERROR HY000: Failed to add the foreign key constaint. Missing index for constraint 'fk_t2_ca' in the referenced table 't1'
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2), ALGORITHM=COPY;
ERROR HY000: Can't create table `test`.`#sql-temporary` (errno: 150 "Foreign key constraint is incorrectly formed")
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2);
ERROR HY000: Failed to add the foreign key constaint. Missing index for constraint 'fk_t2_ca' in the referenced table 't1'
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
ALTER TABLE t2 DROP FOREIGN KEY fk_t2_ca;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1), ALGORITHM=COPY;
ERROR HY000: Can't create table `test`.`#sql-temporary` (errno: 150 "Foreign key constraint is incorrectly formed")
ALTER TABLE t1 MODIFY COLUMN c2 BIGINT(12) NOT NULL;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2), ALGORITHM=COPY;
ERROR HY000: Can't create table `test`.`#sql-temporary` (errno: 150 "Foreign key constraint is incorrectly formed")
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2);
ERROR HY000: Failed to add the foreign key constaint. Missing index for constraint 'fk_t2_ca' in the referenced table 't1'
ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
affected rows: 0
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
affected rows: 1
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
affected rows: 1
CREATE INDEX i_t2_c2_c1 ON t2(c2, c1);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
affected rows: 1
CREATE INDEX i_t2_c3_c1_c2 ON t2(c3, c1, c2);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
affected rows: 1
CREATE INDEX i_t2_c3_c2 ON t2(c3, c2);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
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
affected rows: 1
DROP TABLE t2;
DROP TABLE t1;
CREATE TABLE t1 (a INT, b CHAR(1)) ENGINE=InnoDB;
INSERT INTO t1 VALUES (3,'a'),(3,'b'),(1,'c'),(0,'d'),(1,'e');
CREATE TABLE t2 (a INT, b CHAR(1)) ENGINE=InnoDB;
CREATE TABLE t2i (a INT, b CHAR(1) NOT NULL) ENGINE=InnoDB;
CREATE TABLE t2c (a INT, b CHAR(1) NOT NULL) ENGINE=InnoDB;
INSERT INTO t2 SELECT * FROM t1;
INSERT INTO t2i SELECT * FROM t1;
INSERT INTO t2c SELECT * FROM t1;
BEGIN;
SELECT * FROM t1;
a	b
3	a
3	b
1	c
0	d
1	e
SET lock_wait_timeout=1;
CREATE INDEX t1a ON t1(a);
ERROR HY000: Lock wait timeout exceeded; try restarting transaction
CREATE INDEX t2a ON t2(a);
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
set @old_sql_mode = @@sql_mode;
set @@sql_mode = 'STRICT_TRANS_TABLES';
ALTER TABLE t2i ADD PRIMARY KEY(a,b), ADD INDEX t2a(a), ALGORITHM=INPLACE;
affected rows: 0
info: Records: 0  Duplicates: 0  Warnings: 0
set @@sql_mode = @old_sql_mode;
ALTER TABLE t2c ADD PRIMARY KEY(a,b), ADD INDEX t2a(a), ALGORITHM=COPY;
affected rows: 5
info: Records: 5  Duplicates: 0  Warnings: 0
SELECT * FROM t2i;
ERROR HY000: Table definition has changed, please retry transaction
SELECT * FROM t2i FORCE INDEX(t2a) ORDER BY a;
ERROR HY000: Table definition has changed, please retry transaction
SELECT * FROM t2c;
ERROR HY000: Table definition has changed, please retry transaction
SELECT * FROM t2c FORCE INDEX(t2a) ORDER BY a;
ERROR HY000: Table definition has changed, please retry transaction
SELECT * FROM t2;
a	b
3	a
3	b
1	c
0	d
1	e
SELECT * FROM t2 FORCE INDEX(t2a) ORDER BY a;
ERROR HY000: Table definition has changed, please retry transaction
SELECT * FROM t2;
a	b
3	a
3	b
1	c
0	d
1	e
COMMIT;
SELECT * FROM t2;
a	b
3	a
3	b
1	c
0	d
1	e
SELECT * FROM t2 FORCE INDEX(t2a) ORDER BY a;
a	b
0	d
1	c
1	e
3	a
3	b
SELECT * FROM t2i;
a	b
0	d
1	c
1	e
3	a
3	b
SELECT * FROM t2i FORCE INDEX(t2a) ORDER BY a;
a	b
0	d
1	c
1	e
3	a
3	b
SELECT * FROM t2c;
a	b
0	d
1	c
1	e
3	a
3	b
SELECT * FROM t2c FORCE INDEX(t2a) ORDER BY a;
a	b
0	d
1	c
1	e
3	a
3	b
alter table t2 add index t2a(b);
ERROR 42000: Duplicate key name 't2a'
alter table t2 drop index t2a, add index t2a(b);
show create table t2;
Table	Create Table
t2	CREATE TABLE `t2` (
  `a` int(11) DEFAULT NULL,
  `b` char(1) DEFAULT NULL,
  KEY `t2a` (`b`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
show create table t2i;
Table	Create Table
t2i	CREATE TABLE `t2i` (
  `a` int(11) NOT NULL DEFAULT '0',
  `b` char(1) NOT NULL,
  PRIMARY KEY (`a`,`b`),
  KEY `t2a` (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
show create table t2c;
Table	Create Table
t2c	CREATE TABLE `t2c` (
  `a` int(11) NOT NULL DEFAULT '0',
  `b` char(1) NOT NULL,
  PRIMARY KEY (`a`,`b`),
  KEY `t2a` (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
DROP TABLE t1,t2,t2c,t2i;