if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[hdy]') and OBJECTPROPERTY(id, N'IsUserTable') = 1) drop table [dbo].[hdy] GOCREATE TABLE [dbo].[hdy] ( [F1] [int] NOT NULL , [F2] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL ) ON [PRIMARY] GO insert hdy(F1) values(1)go declare @F1 int,@F2 varchar(30) select @F1=f1,@F2=f2 from hdy if @F2 is null print 'a' else print 'b'
例如 SELECT * FROM A WHERE A IS NULL
例如 SELECT * FROM A WHERE A IS NOT NULL
select * from table where field is not null
SELECT * FROM A WHERE A IS NULL SELECT * FROM A WHERE A IS not NULL SELECT * FROM A WHERE ISNULL(a,'')=''
drop table [dbo].[hdy]
GOCREATE TABLE [dbo].[hdy] (
[F1] [int] NOT NULL ,
[F2] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL
) ON [PRIMARY]
GO
insert hdy(F1) values(1)go
declare @F1 int,@F2 varchar(30)
select @F1=f1,@F2=f2 from hdy
if @F2 is null
print 'a'
else
print 'b'
SELECT * FROM A WHERE A IS NULL
SELECT * FROM A WHERE A IS NOT NULL
SELECT * FROM A WHERE A IS not NULL
SELECT * FROM A WHERE ISNULL(a,'')=''