一个表的字段的外键能否指向同表的主键?

[ltolll]

部门ID(主键)
上级部门ID(能否参考同表的"部门ID"作为外键)?

顶级部门的"级部门ID"可为空.

[rucypli]

可以 mysql> create table test4(a int primary key,b int,foreign key (b) references test4(a)); Query OK, 0 rows affected (0.12 sec) mysql> show create table test4; +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | test4 | CREATE TABLE `test4` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, PRIMARY KEY (`a`), KEY `b` (`b`), CONSTRAINT `test4_ibfk_1` FOREIGN KEY (`b`) REFERENCES `test4` (`a`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 | +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.02 sec) mysql> insert into test4 values(1,1); Query OK, 1 row affected (0.02 sec) mysql> insert into test4 values(1,2); ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'

[ACMAIN_CHM]

可以自参照。

[2399]

这样是可以的

[Rotel-刘志东]

可以的参照完整性。