mysql触发器

DROP TABLE IF EXISTS `user_history`;
CREATE TABLE `user_history` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `user_id` bigint(20) NOT NULL,
  `operatetype` varchar(200) NOT NULL,
  `operatetime` datetime NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

• 创建user表插入事件对应的触发器tri_insert_user；

• 几点说明：

  DELIMITER：改变输入的结束符，默认情况下输入结束符是分号;，这里把它改成了两个分号;;，这样做的目的是把多条含分号的语句做个封装，全部输入完之后一起执行，而不是一遇到默认的分号结束符就自动执行；

  new：当触发插入和更新事件时可用，指向的是被操作的记录

  old： 当触发删除和更新事件时可用，指向的是被操作的记录

• DROP TRIGGER IF EXISTS `tri_insert_user`;
  DELIMITER ;;
  CREATE TRIGGER `tri_insert_user` AFTER INSERT ON `user` FOR EACH ROW begin
      INSERT INTO user_history(user_id, operatetype, operatetime) VALUES (new.id, ‘add a user‘,  now());
  end
  ;;
  DELIMITER ;

   

• 创建user表更新事件对应的触发器tri_update_user；

• DROP TRIGGER IF EXISTS `tri_update_user`;
  DELIMITER ;;
  CREATE TRIGGER `tri_update_user` AFTER UPDATE ON `user` FOR EACH ROW begin
      INSERT INTO user_history(user_id,operatetype, operatetime) VALUES (new.id, ‘update a user‘, now());
  end
  ;;
  DELIMITER ;

   

• 创建user表删除事件对应的触发器tri_delete_user；

• DROP TRIGGER IF EXISTS `tri_delete_user`;
  DELIMITER ;;
  CREATE TRIGGER `tri_delete_user` AFTER DELETE ON `user` FOR EACH ROW begin
      INSERT INTO user_history(user_id, operatetype, operatetime) VALUES (old.id, ‘delete a user‘, now());
  end
  ;;
  DELIMITER ;

  至此，全部表及触发器创建完成，开始验证结果，分别做插入、修改、删除事件，执行以下语句，观察user_history是否自动产生操作记录；

• INSERT INTO user(account, name, address) VALUES (‘user1‘, ‘user1‘, ‘user1‘);
  INSERT INTO user(account, name, address) VALUES (‘user2‘, ‘user2‘, ‘user2‘);
  
  UPDATE user SET name = ‘user3‘, account = ‘user3‘, address=‘user3‘ where name=‘user1‘;
  
  DELETE FROM `user` where name = ‘user2‘;