关于SQL触发器的简单应用

以前不怎么用触发器，现在感觉到它的方便了，可以省去很多不必要的劳动

先建两个表

CREATE TABLE [dbo].[b] (
 [BID] [int] IDENTITY (1, 1) NOT NULL ,
 [AID] [int] NOT NULL ,
 [BStr] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NULL
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[a] (
 [AID] [int] IDENTITY (1, 1) NOT NULL ,
 [AStr] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NULL ,
 [AStr2] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NULL
) ON [PRIMARY]
GO

--------下面分别是insert/delete/update触发器

CREATE TRIGGER [insertA] ON [dbo].[b]
FOR INSERT
AS
begin
insert into a(AStr,AStr2)
select top 1 BStr,BStr from inserted
end 

CREATE TRIGGER [delAID] ON [dbo].[b]
FOR DELETE
AS
delete from a where a.AID in (select AID from deleted)

CREATE TRIGGER [upA] ON [dbo].[b]
FOR UPDATE
AS
if UPDATE(AID) or update(BStr)
begin
 Update a
 Set a.AStr=b.BStr
 From b
 Where a.AID=b.AID
end