CREATE TABLE t1 (
id int(11) NOT NULL PRIMARY KEY,
a int(11) NOT NULL,
b int(11) NOT NULL,
c int not null,
CONSTRAINT test FOREIGN KEY (b) REFERENCES t1 (id)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE t2 (
id int(11) NOT NULL PRIMARY KEY,
a int(11) NOT NULL,
b int(11) NOT NULL,
c int not null,
CONSTRAINT mytest FOREIGN KEY (c) REFERENCES t1(id),
CONSTRAINT test FOREIGN KEY (b) REFERENCES t2 (id)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
ERROR HY000: Can't create table `test`.`t2` (errno: 121 "Duplicate key on write or update")
show warnings;
Level	Code	Message
Warning	121	Create or Alter table `test`.`t2` with foreign key constraint failed. Foreign key constraint `test`.`test` already exists on data dictionary. Foreign key constraint names need to be unique in database. Error in foreign key definition: CONSTRAINT `test` FOREIGN KEY (`b`) REFERENCES `test`.`t2` (`id`).
Error	1005	Can't create table `test`.`t2` (errno: 121 "Duplicate key on write or update")
Warning	1022	Can't write; duplicate key in table 't2'
drop table t1;
create table t1(a int) engine=innodb;
create table t2(a int, constraint a foreign key a (a) references t1(a)) engine=innodb;
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Create  table `test`.`t2` with foreign key `a` constraint failed. There is no index in the referenced table where the referenced columns appear as the first columns.
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t2`
drop table t1;
create table t1(a int unique, b int) engine=innodb;
create table t2(a int, b int, foreign key (a) references t1(a), foreign key (b) references t1(b)) engine=innodb;
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Create  table `test`.`t2` with foreign key (b) constraint failed. There is no index in the referenced table where the referenced columns appear as the first columns.
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t2`
drop table t1;
create table t1(a int not null primary key, b int) engine=innodb;
create table t2(a int, b int, constraint a foreign key a (a) references t1(a),
constraint a foreign key a (a) references t1(b)) engine=innodb;
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t2`
create table t2(a int, b int, constraint a foreign key a (a) references t1(a)) engine=innodb;
alter table t2 add constraint b foreign key (b) references t2(b);
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Alter  table `test`.`t2` with foreign key `b` constraint failed. There is no index in the referenced table where the referenced columns appear as the first columns.
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t2`
drop table t2, t1;
create table t1 (f1 integer primary key) engine=innodb;
alter table t1 add constraint c1 foreign key (f1) references t11(f1);
ERROR HY000: Can't create table `test`.`t1` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Alter  table `test`.`t1` with foreign key `c1` constraint failed. Referenced table `test`.`t11` not found in the data dictionary.
Error	1005	Can't create table `test`.`t1` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t1`
drop table t1;
create temporary table t1(a int not null primary key, b int, key(b)) engine=innodb;
create temporary table t2(a int, foreign key(a) references t1(a)) engine=innodb;
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Create  table `mysqld.1`.`t2` with foreign key constraint failed. Referenced table `mysqld.1`.`t1` not found in the data dictionary close to foreign key(a) references t1(a)) engine=innodb.
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint
alter table t1 add foreign key(b) references t1(a);
ERROR HY000: Can't create table `test`.`#sql-temporary` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Alter  table `mysqld.1`.`t1` with foreign key constraint failed. Referenced table `mysqld.1`.`t1` not found in the data dictionary close to foreign key(b) references t1(a).
Error	1005	Can't create table `test`.`#sql-temporary` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint
create temporary table t2(a int, foreign key(a) references t1(a)) engine=innodb;
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Create  table `test`.`t2` with foreign key constraint failed. Temporary tables can't have foreign key constraints.
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t2`
alter table t1 add foreign key(b) references t1(a);
ERROR HY000: Can't create table `test`.`t1` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Alter  table `test`.`t1` with foreign key constraint failed. Temporary tables can't have foreign key constraints.
Error	1005	Can't create table `test`.`t1` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t1`
drop table t1;
create table t1(a int not null primary key, b int, key(b)) engine=innodb;
alter table t1 add foreign key(a,b) references t1(a);
ERROR 42000: Incorrect foreign key definition for 'foreign key without name': Key reference and table reference don't match
show warnings;
Level	Code	Message
Error	1239	Incorrect foreign key definition for 'foreign key without name': Key reference and table reference don't match
drop table t1;
create table t1(a int not null primary key, b int, key(b)) engine=innodb;
alter table t1 add foreign key(a) references t1(a,b);
ERROR 42000: Incorrect foreign key definition for 'foreign key without name': Key reference and table reference don't match
show warnings;
Level	Code	Message
Error	1239	Incorrect foreign key definition for 'foreign key without name': Key reference and table reference don't match
drop table t1;
create table t1 (f1 integer not null primary key) engine=innodb;
alter table t1 add constraint c1 foreign key (f1) references t1(f1) on update set null;
ERROR HY000: Can't create table `test`.`t1` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Alter  table `test`.`t1` with foreign key `c1` constraint failed. You have defined a SET NULL condition but column 'f1' is defined as NOT NULL.
Error	1005	Can't create table `test`.`t1` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t1`
create table t2(a int not null, foreign key(a) references t1(f1) on delete set null) engine=innodb;
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Create  table `test`.`t2` with foreign key (a) constraint failed. You have defined a SET NULL condition but column 'a' is defined as NOT NULL.
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t2`
drop table t1;
create table t1 (id int not null primary key, f1 int, f2 int, key(f1)) engine=innodb;
create table t2(a char(20), key(a), foreign key(a) references t1(f1)) engine=innodb;
ERROR HY000: Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
show warnings;
Level	Code	Message
Warning	150	Create  table `test`.`t2` with foreign key (a) constraint failed. Field type or character set for column 'a' does not mach referenced column 'f1'.
Error	1005	Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")
Warning	1215	Cannot add foreign key constraint for `t2`
drop table t1;