On delete cascade to table

Question

如何将删除级联添加到这个表创建脚本中？id_fk来自于mytable表。

 CREATE TABLE IF NOT EXISTS `ip` (

  `ip_id` int(11) NOT NULL AUTO_INCREMENT,

  `id_fk` int(11) DEFAULT NULL,

  `ip_add` varchar(40) DEFAULT NULL,

  PRIMARY KEY (`ip_id`),

  KEY `id_fk` (`id_fk`)

) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=1;

Answer 1

试试这个：

ALTER TABLE `ip`
ADD CONSTRAINT `FK_mytable` FOREIGN KEY (`id_fk`) REFERENCES `mytable` (`id`)   
ON DELETE CASCADE ON UPDATE CASCADE;

希望这能有所帮助！

Answer 2

添加foreign key constraint并指定要执行的操作和执行的时间。

 ALTER TABLE ip
    ADD CONSTRAINT constraint_name
        FOREIGN KEY index_name(id_fk)
            REFERENCES other_table(other_column_name)
                ON DELETE CASCADE
                ON UPDATE CASCADE;

您可以在表定义中直接包含约束：

FOREIGN KEY index_name(id_fk)
    REFERENCES other_table(other_column_name)
        ON DELETE CASCADE
        ON UPDATE CASCADE;