create table tt
(
aa int ,
bb int ,
cc varchar(08)
)
insert into tt
select 1, 255 , '20161212' union
select 1, 15 , '20161210' union
select 2, 33 , '20160612' union
select 2, 11 , '20160101'
select a.*
from tt a
where not exists
(select 1 from tt where aa = a.aa and cc > a.cc)