--sample Data
declare @tbl table
(
id int
,field_1 date
,field_2 date
,field_3 date
)
insert into @tbl values(1,'20120823','20120824','20120825')
--Query
select max(a.mydate),a.id
from (
select id,field_1 mydate from @tbl
union all
select id,field_2 from @tbl
union all
select id,field_3 from @tbl
)a
group by a.id
I think this is what you require.... Please provide some sample day from next time.. So, that it will be easy to answer