插入更新触发器如何判断是插入还是更新

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我需要在表 A 上编写一个插入、更新触发器，它将删除表 B 中的所有行，这些行的一列(比如 Desc)的值类似于在表 A 的列(比如 Col1)中插入/更新的值.我将如何编写它以便我可以处理更新和插入情况.我如何确定触发器是为更新还是插入执行的.

I need to write an Insert, Update Trigger on table A which will delete all rows from table B whose one column (say Desc) has values like the value inserted/updated in the table A's column (say Col1). How would I go around writing it so that I can handle both Update and Insert cases. How would I determine if the trigger is executed for an update or insert.

推荐答案

触发器有特殊的 INSERTED 和 DELETED 表来跟踪之前"和之后"数据.所以你可以使用类似 IF EXISTS (SELECT * FROM DELETED) 的东西来检测更新.更新时您只有 DELETED 中的行，但 INSERTED 中总是有行.

Triggers have special INSERTED and DELETED tables to track "before" and "after" data. So you can use something like IF EXISTS (SELECT * FROM DELETED) to detect an update. You only have rows in DELETED on update, but there are always rows in INSERTED.

寻找插入"在创建触发器中.

编辑，2011 年 11 月 23 日

Edit, 23 Nov 2011

评论后，此答案仅适用于 INSERTED 和 UPDATED 触发器.显然，DELETE 触发器不能有INSERTED 中的总是行"；正如我上面所说的

After comment, this answer is only for INSERTED and UPDATED triggers. Obviously, DELETE triggers can not have "always rows in INSERTED" as I said above