怎么消除重复值

create table tb(fdate datetime,fscstockid int,fitemid int)
insert into tb select '2008-02-20 00:00:00.000',130,512
union all select '2008-01-20 00:00:00.000',130,568
union all select '2008-01-01 00:00:00.000',132,1040
union all select '2008-01-07 00:00:00.000',132,1040
union all select '2008-01-09 00:00:00.000',132,1040
union all select '2008-01-10 00:00:00.000',132,1040
union all select '2008-01-07 00:00:00.000',132,1042
union all select '2008-01-09 00:00:00.000',132,1042
union all select '2008-01-10 00:00:00.000',132,1042

select * from tb

select A.* from tb A where not exists(select 1 from tb where fscstockid=A.fscstockid and fitemid=A.fitemid and fdate > A.fdate)