录入A、B表对比，如果记录数据完全相同，就插入C表，但为什么不能处理空值的情况?
SET   QUOTED_IDENTIFIER   ON  
GO
SET   ANSI_NULLS   OFF  
GO

ALTER           TRIGGER   [CHECK_A]   ON   [DBO].[A]  
FOR   INSERT,UPDATE
AS
DECLARE   @I   INT       ---审核状态   1:审核通过   0:审核不通过   -1:未审核

SET   ANSI_NULLS   OFF  

-----------------------添加数据-------------------------
IF   NOT   EXISTS(SELECT   1   FROM   B   WHERE   ID=(SELECT   ID   FROM   INSERTED))
SET   @I=-1

IF   EXISTS(SELECT   1   FROM   B   WHERE   ID=(SELECT   ID   FROM   INSERTED)   AND   T1=(SELECT   T1   FROM   INSERTED)   AND   T2=(SELECT   T2   FROM   INSERTED))  
SET   @I=1

IF   EXISTS(SELECT   1   FROM   B   WHERE   ID=(SELECT   ID   FROM   INSERTED))
AND   NOT   EXISTS(SELECT   1   FROM   B   WHERE   ID=(SELECT   ID   FROM   INSERTED)   AND   T1=(SELECT   T1   FROM   INSERTED)   AND   T2=(SELECT   T2   FROM   INSERTED))  
SET   @I=0

IF   @I=1  
BEGIN

INSERT   INTO   T(ID,T1,T2)
SELECT   ID,T1,T2   FROM   INSERTED

ALTER   TABLE   [DBO].[A]   DISABLE   TRIGGER   ALL
ALTER   TABLE   [DBO].[B]   DISABLE   TRIGGER   ALL

UPDATE   A   SET   checkstat=1   WHERE   ID=(SELECT   ID   FROM   INSERTED)
UPDATE   B   SET   checkstat=1   WHERE   ID=(SELECT   ID   FROM   INSERTED)

ALTER   TABLE   [DBO].[A]   ENABLE   TRIGGER   ALL
ALTER   TABLE   [DBO].[B]   ENABLE   TRIGGER   ALL

END    

IF   @I=0  
BEGIN

ALTER   TABLE   [DBO].[A]   DISABLE   TRIGGER   ALL
ALTER   TABLE   [DBO].[B]   DISABLE   TRIGGER   ALL

UPDATE   A   SET   checkstat=0   WHERE   ID=(SELECT   ID   FROM   INSERTED)
UPDATE   B   SET   checkstat=0   WHERE   ID=(SELECT   ID   FROM   INSERTED)

ALTER   TABLE   [DBO].[A]   ENABLE   TRIGGER   ALL
ALTER   TABLE   [DBO].[B]   ENABLE   TRIGGER   ALL

END  


GO
SET   QUOTED_IDENTIFIER   OFF  
GO
SET   ANSI_NULLS   ON  
GO


----------------------------------
上面是A表的触发器，B表中的触发器与此类似，如果A、B表中ID相同的记录，其对应字段的值完全相同，就插入C表，可是当A、B表对应字段都是NULL时，就无法处理了，已经在触发器前加了SET   ANSI_NULLS   OFF   语句，为什么还是不能判断呢？


------解决方案--------------------
这触发器在一次操作多条记录的时候肯定有问题

------解决方案--------------------
ALTER TRIGGER [CHECK_A] ON [DBO].[A]
FOR INSERT,UPDATE
AS

INSERT INTO T(ID,T1,T2)
SELECT ID,T1,T2 FROM INSERTED i,b
where i.id=b.id
and (i.T1=b.T1 or i.T1 is null and b.T1 is null)
and (i.T2=b.T2 or i.T2 is null and b.T2 is null)



ALTER TABLE [DBO].[A] DISABLE TRIGGER ALL
ALTER TABLE [DBO].[B] DISABLE TRIGGER ALL

UP