mysql--觸發器語法

例子：創建觸發器，記錄表的增、刪、改操作記錄

//創建user表；
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `account` varchar(255) DEFAULT NULL,
  `name` varchar(255) DEFAULT NULL,
  `address` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

//創建對user表操作歷史表
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;

DELIMITER：改變輸入的結束符，默認情況下輸入結束符是分號;，這裏把它改成了兩個分號;;，這樣做的目的是把多條含分號的語句做個封裝，全部輸入完之後一起執行，而不是一遇到默認的分號結束符就自動執行；

new：當觸發插入和更新事件時可用，指向的是被操作的記錄

old： 當觸發刪除和更新事件時可用，指向的是被操作的記錄

INSERT:

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 ;

UPDATE:

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 ;

DELETE:

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 ;