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DROP TABLE IF EXISTS t1, t2;
CREATE TABLE t1 (a <INT_COLUMN>,
b <CHAR_COLUMN>,
<CUSTOM_INDEX> (a)
) ENGINE=<STORAGE_ENGINE> <CUSTOM_TABLE_OPTIONS>;
CREATE TABLE t2 (a <INT_COLUMN>,
b <CHAR_COLUMN>,
FOREIGN KEY (a) REFERENCES t1(a)
) ENGINE=<STORAGE_ENGINE> <CUSTOM_TABLE_OPTIONS>;
SHOW CREATE TABLE t2;
Table Create Table
t2 CREATE TABLE `t2` (
`a` int(11) DEFAULT NULL,
`b` char(8) DEFAULT NULL,
KEY `a` (`a`),
CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`)
) ENGINE=<STORAGE_ENGINE> DEFAULT CHARSET=latin1
INSERT INTO t2 (a,b) VALUES (1,'a'),(2,'b');
ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`))
INSERT INTO t1 (a,b) VALUES (1,'c'),(2,'d');
INSERT INTO t2 (a,b) VALUES (1,'a'),(2,'b');
UPDATE t2 SET a=a+1;
ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`))
UPDATE t1 SET a=3 WHERE a=2;
ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`))
DELETE FROM t1 WHERE a=2;
ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`))
DELETE FROM t2 WHERE a=2;
SELECT a,b FROM t1;
a b
1 c
2 d
SELECT a,b FROM t2;
a b
1 a
DROP TABLE t1;
ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails
DROP TABLE t2;
CREATE TABLE t2 (a <INT_COLUMN>,
b <CHAR_COLUMN>,
FOREIGN KEY (a) REFERENCES t1(a)
ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=<STORAGE_ENGINE> <CUSTOM_TABLE_OPTIONS>;
SHOW CREATE TABLE t2;
Table Create Table
t2 CREATE TABLE `t2` (
`a` int(11) DEFAULT NULL,
`b` char(8) DEFAULT NULL,
KEY `a` (`a`),
CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=<STORAGE_ENGINE> DEFAULT CHARSET=latin1
INSERT INTO t2 (a,b) VALUES (1,'a'),(2,'b'),(3,'c'),(4,'d');
ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`) ON DELETE CASCADE ON UPDATE CASCADE)
INSERT INTO t1 (a,b) VALUES (3,'a'),(4,'a');
INSERT INTO t2 (a,b) VALUES (1,'a'),(2,'b'),(3,'c'),(4,'d'),(4,'e'),(3,'a');
UPDATE t1 SET a=a+1;
SELECT a,b FROM t2;
a b
5 a
5 a
5 b
5 c
5 d
5 e
DELETE FROM t1 WHERE b='a' LIMIT 2;
SELECT a,b FROM t2;
a b
TRUNCATE TABLE t1;
ERROR 42000: Cannot truncate a table referenced in a foreign key constraint (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `test`.`t1` (`a`))
DROP TABLE t2;
DROP TABLE t1;
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