SQL创建表外键约束的语句是什么

mysql> ALTER TABLE tb_emp2

    -> ADD CONSTRAINT fk_tb_dept1

    -> FOREIGN KEY(deptId)

    -> REFERENCES tb_dept1(id);

Query OK, 0 rows affected (1.38 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`),

  CONSTRAINT `fk_tb_dept1` FOREIGN KEY (`deptId`) REFERENCES `tb_dept1` (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=gb2312

1 row in set (0.12 sec)