select * from a

where ax in (select ax from a group by ax having count(ax) > 1)

------解决方案--------------------
SQL code

--保留一条（这个应该是大多数人所需要的 ^_^）

Delete a Where ID Not In (Select Max(ID) From a Group By Title)

------解决方案--------------------

declare @t table(id int);

insert into @t
 select 1 union all
 select 2 union all
 select 3 union all
 select 2 union all
 select 1  

;with c1 as
(
 select row_number() over(partition by id order by id) rowid,
		  id
 from @t
)
delete from c1 where rowid > 1

select * from @t order by id


id
-----------
1
2
3

(3 行受影响)




------解决方案--------------------
用distinct 最简单了。不过显示最新插入的也行，

select id,f1,f2 from t tt
where tt.id=
(select max(id)
from t
where tt.f1=t.f1 and tt.f2=t.f2)