Question

我的触发器有问题（添加和删除）：

ALTER TRIGGER [trgAfterShoppingInserted]
ON [ShopingList] AFTER INSERT 
AS BEGIN
   DECLARE @cardId char(6), @points int, @userId int

   SET @cardId = (SELECT cardId FROM inserted)
   SET @points = (SELECT points FROM inserted)
   SET @userId = (SELECT userId from [Card] WHERE id = @cardId)
   IF @userId = 0
   BEGIN
   Update [Card]
   set points = points + @points
   where id =@cardId
   END
   ELSE
   Update [Card]
   set points = points + @points
   where id =@cardId OR
   userId = @userId
END


ALTER TRIGGER [trgAfterShoppingDeleted]
ON [ShopingList] AFTER DELETE 
AS BEGIN
   DECLARE @cardId char(6), @points int, @userId int

   SET @cardId = (SELECT cardId FROM inserted)
   SET @points = (SELECT points FROM inserted)
   SET @userId = (SELECT userId from [Card] WHERE id = @cardId)
   IF @userId = 0
   BEGIN
   Update [Card]
   set points = points - @points
   where id =@cardId
   END
   ELSE
   Update [Card]
   set points = points - @points
   where id =@cardId OR
   userId = @userId
END

问题出在SET @cardId..

上

错误是：

子查询返回的值超过1。当子查询遵循=，！=，＆lt;，＆lt; =，＆gt;，＆gt; =或子查询用作表达式时，不允许这样做。

怎么可能？

感谢您的帮助

Answer 1

如果insert或delete语句应插入或删除多行，则两个触发器都不起作用。你需要停止假设你的触发器只处理一行 - 事实并非如此。您需要重写触发器以同时处理多个行（在Inserted和Deleted表中）

作为一个例子 - 您可以重写trgAfterShoppingDeleted这样的内容：

ALTER TRIGGER [trgAfterShoppingDeleted]
ON [ShopingList] AFTER DELETE 
AS BEGIN
   UPDATE [Card]
   SET points = points - i.points
   FROM Inserted i
   WHERE Card.id = i.id AND i.UserId = 0

   UPDATE [Card]
   SET points = points - @points
   FROM Inserted i
   WHERE i.UserId <> 0 AND (Card.id = i.id OR Card.userId = i.userId)
END

您需要考虑数据集 - 不要假设触发器伪表中有单行，也不要在触发器中执行RBAR（逐行激动行）处理

Answer 2

deleted表包含作为给定DELETE语句的一部分删除的记录，如果DELETE条件与多条记录匹配，则可以包含多行。

这就是您的情况，当您尝试从包含多个记录的cardId表中选择deleted时，select语句返回多个值，因此触发器会抛出该异常。

删除后删除触发器的值

2 个答案: