这个简单的MySQL触发器的语法有什么问题？

Question

DELIMITER $$ 

CREATE TRIGGER ad_user AFTER DELETE 

ON `user` 
FOR EACH ROW BEGIN 
    DECLARE max_id INT; 
    DECLARE new_id INT; 

    SELECT MAX(`id`) INTO max_id FROM `user`; 
    IF max_id = NULL THEN 
     SET max_id = 0; 
    END IF 

    SELECT `new_id` INTO new_id FROM `conf` WHERE `table` = 'user'; 

    IF max_id < new_id THEN 
     UPDATE `conf` SET `new_id` = max_id WHERE `table` = 'user'; 
    END IF 
END$$ 

我得到了以下错误提示，当我创建这个触发器：

错误代码：1064你在你的SQL语法错误;检查 手册，该手册对应于您的MySQL服务器版本的右边 语法以在'SELECT new_id INTO new_id FROM conf WHERE table = 'fact''附近使用。 IF max_id < new_id THEN'at line 12

任何人都可以帮助我？提前致谢！

Answer 1

试着写了这样的查询：

DELIMITER $$ 

CREATE TRIGGER ad_user AFTER DELETE 
ON `user` 
FOR EACH ROW BEGIN 
    DECLARE v_max_id INT; 
    DECLARE v_new_id INT; 

    SELECT MAX(`id`) INTO v_max_id FROM `user`; 
    IF v_max_id IS NULL THEN 
     SET v_max_id = 0; 
    END IF; 

    SELECT `new_id` INTO v_new_id FROM `conf` WHERE `table` = 'user'; 

    IF v_max_id < v_new_id THEN 
     UPDATE conf c 
      SET c.new_id = v_max_id 
      WHERE c.`table` = 'user'; 
    END IF; 
END$$ 

这主要增加了分号和修复= NULL。