求一个sql语句~~~大侠拜托了。。。

[zzw165027967]

比如有个表table
id col datetime
1 aa 2012-01-01
2 aa 2012-01-03
3 bb 2012-03-01
4 cc 2011-10-12
5 bb 2013-11-11

我要得到
2 aa 2012-01-03
5 bb 2013-11-11
4 cc 2011-10-12


就是col字段相同的，只取datetime最后的那一条记录~~拜托了~~

[AcHerat]

select *
from tb t
where not exists (select 1 from tb where col=t.col and date>t.date)

[AcHerat]

select *
from tb t
where id = (select top 1 id from tb where col=t.col order by date desc)

select *
from tb t
where date = (select max(date) from tb where col=t.col)

select *
from(
    select *,rid=row_number() over (partition by col order by date desc)
    from tb
)t
where rid = 1

-- ...

[迪迦凹凸曼]

select id,col,max(datetime)
from tb
group by id,col