UNIQUE Key Constarint Voilation In Sqlserver 2005

Hi,


I have created a table with 4 columns (SQL2005 server):

CREATE TABLE test(
userid smallint IDENTITY (1, 1) NOT NULL ,
name nvarchar (15) COLLATE Lithuanian_CI_AS NULL ,
empnumber nvarchar (14) COLLATE Lithuanian_CI_AS NULL,Description nvarchar (14) COLLATE Lithuanian_CI_AS NOT NULL
GO
ALTER TABLE test WITH NOCHECK ADD
CONSTRAINT PK_user PRIMARY KEY CLUSTERED (userid)
GO
ALTER TABLE test ADD
CONSTRAINT UK_user_name UNIQUE NONCLUSTERED (name),
CONSTRAINT UK_user_empnumber UNIQUE NONCLUSTERED (empnumber )
GO



The table has few records:

INSERT INTO test (name,Description ) VALUES ('laks','abcd')When I try to insert one more record with NULL value

INSERT INTO test (name,Description ) VALUES ('kusuma','hjjk')
GO
I get error message:

Error: Violation of UNIQUE KEY constraint 'UK_user_Name'. Cannot insert duplicate key in object 'user'. I want both(name and empnumber) coloumns to be unique and allow nulls.So how can i proceed further to achieve the same.Psl help me. ThanksKusuma