触发器：当发生某一个动作（增、删、改）将会触发的代码

什么时候需要：比如删除某列的时候，可能因为是别的表的外键而删除失败

1 /*删除新闻类别后的动作*/ 2 ALTER TRIGGER [dbo].[trigCategoryDelete] 3     ON [dbo].[category] 4     AFTER DELETE 5 AS 6 BEGIN 7     ...... 8 END 9 10 /*删除新闻类别以及类别下的全部新闻*/11 ALTER TRIGGER [dbo].[trigCategoryDelete]12     ON [dbo].[category]13     instead of DELETE14 AS15 BEGIN16     declare @id int17     select @id=id from deleted18     delete news where caId=@id19     delete category where id=@id        20 END

/*删除新闻类别以及类别下的全部新闻以及新闻的评论*/ ALTER TRIGGER [dbo].[trigCategoryDelete]    ON [dbo].[category]     instead of DELETE AS BEGIN     declare @caId int     select @caId=id from deleted     delete comment where newsId in (select newsId from news where caId=@caId)     delete news where caId=@id     delete category where id=@id         END