MySql串聯刪除和更新

（一）利用外鍵實現串聯刪除

1、先建立測試資料庫

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：資料表必須使用InnoDB引擎。

           外鍵必須建立索引

          外鍵綁定關係使用了“ on delete cascade ”

2、插入測試資料

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、查看資料表的狀態

4、實驗串聯刪除功能

只刪除roottb表中id為2的資料記錄，看看subtb表中rootid為2的相關子紀錄是否會自動刪除！

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)

以上部分轉自於：bbs.chinaunix.net/forum.php?mod=viewthread&tid=462977

（二）利用觸發器實現串聯刪除

下面給出執行個體

1、建立測試資料庫

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、插入測試資料

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（級聯/同步）刪除的觸發器

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、刪除root_trigger表中的id=2的記錄，再查看sub_trigger中rootid=2的記錄是否刪除

刪除成功即實現了，觸發器的串聯刪除！