Trigger的用法及Inserted Deleted的作用

Table Name:   TB_1,TB_2   （两个table 结构完全一样）

Create Table TB_1(ID Int, Name_1 varchar(20),Status varchar(20) ,Type Varchar(20))

Create Table TB_2(ID Int, Name_1 varchar(20),Status varchar(20) ,Type Varchar(20))

-- 为Tb_1创建Trigger, 当 TB_1 发生变化时，变化的信息（Insert ,Update,Delete）将保存于 TB_2 中,Update是两条记录，Update 之前和之后 都要保存盐类

Create trigger Trig_t2
On Tb_1
For Insert,Update,Delete
As
declare @id int,
          @name_1 varchar(20),
   @status varchar(20)

If not exists(Select 1 from deleted)   ----Insert
    Begin
     select @id=id, @name_1=name_1,@status=status from inserted
     insert into tb_2(id,name_1,status,type)values(@id,@name_1,@status,'Insert')
    End

If exists(select 1 from inserted) and exists(select 1 from deleted) ---Update
Begin
     /* Update Before */
     select @id=id, @name_1=name_1,@status=status from deleted
     insert into tb_2(id,name_1,status,type)values(@id,@name_1,@status,'UpdateBefor')

     /* Update End */
     select @id=id, @name_1=name_1,@status=status from inserted
     insert into tb_2(id,name_1,status,type)values(@id,@name_1,@status,'UpdateEnd')
End

If not exists(select 1 from inserted) ---Delete
Begin
    
     select @id=id, @name_1=name_1,@status=status from inserted
     insert into tb_2(id,name_1,status,type)values(@id,@name_1,@status,'Delete')
End

----测试----

insert into tb_1(id,name_1,status)values('1','1','1')
select * from tb_1
select * from tb_2

id          name_1               status               type                                              
----------- -------------------- -------------------- --------------------------------------------------
1           1                    1                    NULL

(1 row(s) affected)

id          name_1               status               type                                              
----------- -------------------- -------------------- --------------------------------------------------
1           1                    1                    Insert


-----------测试Update---------------

update tb_1 set name_1='2'where id='1'

select * from tb_1
select * from tb_2

id          name_1               status               type                                              
----------- -------------------- -------------------- --------------------------------------------------
1           2                    1                    NULL

(1 row(s) affected)

id          name_1               status               type                                              
----------- -------------------- -------------------- --------------------------------------------------
1           1                    1                    Insert
1           1                    1                    UpdateBefor
1           2                    1                    UpdateEnd