MySql级联删除和更新

来源：互联网发布：espace uc mac 编辑：程序博客网时间：2024/04/28 08:25

（一）利用外键实现级联删除

1、先建立测试数据库

CREATE TABLE `roottb` (  `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL,  `data` VARCHAR(100) NOT NULL DEFAULT '',  PRIMARY KEY (`id`)) TYPE=InnoDB;CREATE TABLE `subtb` (  `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL,  `rootid` INT(11) UNSIGNED NOT NULL DEFAULT '0',  `data` VARCHAR(100) NOT NULL DEFAULT '',  PRIMARY KEY (`id`),  INDEX (`rootid`),  FOREIGN KEY (`rootid`) REFERENCES roottb(`id`) ON DELETE CASCADE) TYPE=InnoDB;

注意：数据表必须使用InnoDB引擎。

外键必须建立索引

外键绑定关系使用了“ on delete cascade ”

2、插入测试数据

INSERT INTO `roottb` (`id`,`data`)  VALUES ('1', 'test root line 1'),         ('2', 'test root line 2'),         ('3', 'test root line 3');INSERT INTO `subtb` (`id`,`rootid`,`data`)  VALUES ('1', '1', 'test sub line 1 for root 1'),         ('2', '1', 'test sub line 2 for root 1'),         ('3', '1', 'test sub line 3 for root 1'),         ('4', '2', 'test sub line 1 for root 2'),         ('5', '2', 'test sub line 2 for root 2'),         ('6', '2', 'test sub line 3 for root 2'),         ('7', '3', 'test sub line 1 for root 3'),         ('8', '3', 'test sub line 2 for root 3'),         ('9', '3', 'test sub line 3 for root 3');

3、查看数据表的状态

4、试验级联删除功能

只删除roottb表中id为2的数据记录，看看subtb表中rootid为2的相关子纪录是否会自动删除！

mysql>; delete from `roottb` where `id`='2';Query OK, 1 row affected (0.03 sec)mysql>; select * from `roottb`;+----+------------------+| id | data             |+----+------------------+|  1 | test root line 1 ||  3 | test root line 3 |+----+------------------+2 rows in set (0.00 sec)mysql>; select * from `subtb`;+----+--------+----------------------------+| id | rootid | data                       |+----+--------+----------------------------+|  1 |      1 | test sub line 1 for root 1 ||  2 |      1 | test sub line 2 for root 1 ||  3 |      1 | test sub line 3 for root 1 ||  7 |      3 | test sub line 1 for root 3 ||  8 |      3 | test sub line 2 for root 3 ||  9 |      3 | test sub line 3 for root 3 |+----+--------+----------------------------+6 rows in set (0.01 sec)

以上部分转自于：bbs.chinaunix.net/forum.php?mod=viewthread&tid=462977

（二）利用触发器实现级联删除

下面给出实例

1、建立测试数据库

CREATE TABLE `root_trigger` (  `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL,  `data` VARCHAR(100) NOT NULL DEFAULT '',  PRIMARY KEY (`id`));CREATE TABLE `sub_trigger` (  `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL,  `rootid` INT(11) UNSIGNED NOT NULL DEFAULT '0',  `data` VARCHAR(100) NOT NULL DEFAULT '',  PRIMARY KEY (`id`)  );

2、插入测试数据

INSERT INTO `root_trigger` (`id`,`data`)  VALUES ('1', 'test root line 1'),         ('2', 'test root line 2'),         ('3', 'test root line 3');INSERT INTO `sub_trigger` (`id`,`rootid`,`data`)  VALUES ('1', '1', 'test sub line 1 for root 1'),         ('2', '1', 'test sub line 2 for root 1'),         ('3', '1', 'test sub line 3 for root 1'),         ('4', '2', 'test sub line 1 for root 2'),         ('5', '2', 'test sub line 2 for root 2'),         ('6', '2', 'test sub line 3 for root 2'),         ('7', '3', 'test sub line 1 for root 3'),         ('8', '3', 'test sub line 2 for root 3'),         ('9', '3', 'test sub line 3 for root 3');

3、建立（级联/同步）删除的触发器

drop trigger if exists t_afterdelete_on_sub;create trigger t_afterdelete_on_subafter delete on root_triggerfor each rowbegin       delete from sub_trigger where rootid=old.id;      end;

4、删除root_trigger表中的id=2的记录，再查看sub_trigger中rootid=2的记录是否删除

删除成功即实现了，触发器的级联删除！