触发器 (AFTER/BEFORE) 在 Mysql

Question

我有一个工作正常的触发器。

CREATE TRIGGER crm_listings__au 
AFTER UPDATE 
ON crm_listings FOR EACH ROW
    INSERT INTO crm_listings_versions 
        SELECT 
            'update', NULL, NOW(), NULL, d.*
        FROM 
            crm_listings AS d 
        WHERE 
            d.id = NEW.id;

现在我还想跟踪字段列名。我想我不能在上面的查询中做所以我改为下面的触发器

CREATE TRIGGER crm_listings__au 
BEFORE UPDATE 
ON crm_listings 
FOR EACH ROW
BEGIN
    IF OLD.type != NEW.type
    THEN
        INSERT INTO crm_listings_versions  
            SELECT 
                'update', NULL, NOW(), 'type', d.* 
            FROM 
                crm_listings AS d 
            WHERE 
                d.id = NEW.id;
    END IF;

    IF OLD.price != NEW.price
    THEN
        INSERT INTO crm_listings_versions 
            SELECT  
                'update', NULL, NOW(), 'price', d.* 
            FROM 
                crm_listings AS d
            WHERE 
                d.id = NEW.id;
    END IF;
END;
$$

当我运行这段代码时，我得到这个错误：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 10

更新：

我在 Whosebug

上关注了这个 post

Answer 1

@kordirko: Can you please explain a little bit?

请研究文档：http://dev.mysql.com/doc/refman/5.7/en/stored-programs-defining.html

If you use the mysql client program to define a stored program containing semicolon characters, a problem arises. By default, mysql itself recognizes the semicolon as a statement delimiter, so you must redefine the delimiter temporarily to cause mysql to pass the entire stored program definition to the server.

To redefine the mysql delimiter, use the delimiter command. The following example shows how to do this for the dorepeat() procedure just shown. The delimiter is changed to // to enable the entire definition to be passed to the server as a single statement, and then restored to ; before invoking the procedure. This enables the ; delimiter used in the procedure body to be passed through to the server rather than being interpreted by mysql itself.

简单示例 - 我正在使用 MySql Workbench 并复制并粘贴了您的触发器。首先是一些虚拟表：

create table crm_listings(
   id int,
   type int,
   price int
);

create table crm_listings_versions(
   ttype varchar(100),
   something varchar(100),
   d date,
   something1 varchar(100),
   id int,
   type int,
   price int
);

现在我运行你的代码 没有分隔符

CREATE TRIGGER crm_listings__au BEFORE UPDATE ON crm_listings 

FOR EACH ROW

 BEGIN
    IF OLD.type != NEW.type
    THEN


        INSERT INTO crm_listings_versions SELECT 'update', NULL, NOW(), 'type', d.* FROM crm_listings AS d WHERE d.id = NEW.id;

    END IF;
    IF OLD.price != NEW.price
    THEN


        INSERT INTO crm_listings_versions SELECT 'update', NULL, NOW(), 'price', d.* FROM crm_listings AS d WHERE d.id = NEW.id;

    END IF;
END;
$$

Error Code: 1064. You have an error in your SQL syntax; check the manual 
that corresponds to your MySQL server version 
for the right syntax to use near '' at line 10  0.000 sec

结果=错误

然后相同，但使用 DELIMITER 命令：

DELIMITER $$
CREATE TRIGGER crm_listings__au BEFORE UPDATE ON crm_listings 

FOR EACH ROW

 BEGIN
    IF OLD.type != NEW.type
    THEN


        INSERT INTO crm_listings_versions SELECT 'update', NULL, NOW(), 'type', d.* FROM crm_listings AS d WHERE d.id = NEW.id;

    END IF;
    IF OLD.price != NEW.price
    THEN


        INSERT INTO crm_listings_versions SELECT 'update', NULL, NOW(), 'price', d.* FROM crm_listings AS d WHERE d.id = NEW.id;

    END IF;
END;
$$

DELIMITER ;

0 row(s) affected

结果=成功

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