mysql怎么取消外键限制（约束）？

mysql> ALTER TABLE tb_emp2

    -> DROP FOREIGN KEY fk_tb_dept1;

Query OK, 0 rows affected (0.19 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> SHOW CREATE TABLE tb_emp2\G

*************************** 1. row ***************************

       Table: tb_emp2

Create Table: CREATE TABLE `tb_emp2` (

  `id` int(11) NOT NULL,

  `name` varchar(30) DEFAULT NULL,

  `deptId` int(11) DEFAULT NULL,

  `salary` float DEFAULT NULL,

  PRIMARY KEY (`id`),

  KEY `fk_tb_dept1` (`deptId`)

) ENGINE=InnoDB DEFAULT CHARSET=gb2312

1 row in set (0.00 sec)