mysql - 创建触发器以使用另一个表的更改来更新表

Question

我有一个包含两个表的数据库。他们是，

顺序(用户ID，名称，索引，总计)

userid | total

sandun | 2500
sandun | 4800
akmal  | 1200

paynow(userid,totalpayment)

userid  | totalpayment
sandun  | 14000
akmal   | 22500

我需要在订单表中插入对应的用户 ID 时更新 paynow 表。所以我为此做了一个触发器。就在这里，

CREATE TRIGGER totals
AFTER INSERT ON orders
FOR EACH ROW
BEGIN
WHEN(NEW.userid IS NOT NULL)
UPDATE paynow
SET totalpayment = totalpayment + NEW.total
WHERE userid = NEW.userid
END;

但它给出了这个错误。

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHEN(NEW.userid IS NOT NULL) UPDATE paynow SET totalpayment = totalpayment + N' at line 5

Answer 1

MySQL 触发器没有 when 子句。您可以改用 if 语句:

CREATE TRIGGER totals
AFTER INSERT ON orders
FOR EACH ROW
BEGIN
IF NEW.userid IS NOT NULL THEN
    UPDATE paynow
    SET totalpayment = totalpayment + NEW.total
    WHERE userid = NEW.userid;
END IF;
END;