关于SQL,该怎么解决

关于SQL
数据如下

time cs_cmid CS_Follow
2011-11-27 1 1,2,3,4
2011-12-06 2 1,2,3
2011-12-05 2 1,3,4
2011-12-03 2 1,7,9
2011-12-03 3 1,7,9
2011-11-30 3 2,3

根据cs_cmid分组,在同一组的取time最大一条数据，最后结果应为
2011-11-27 1 1,2,3,4
2011-12-06 2 1,2,3
2011-12-03 3 1,7,9

没想通要怎么弄，求高手指点

------解决方案--------------------
select *
from tbname k
where not exists(select * from tbname where 
 time =k.time and k.cs_cmid<cs_cmid
)

------解决方案--------------------
select max(time) as time,cs_cmid from tbname group by cs_cmid
然后再去join查一下CS_Follow值就行了
------解决方案--------------------

SQL code

select * from tbname k
where exists(select 1 from tbname where  
 cs_cmid=k.cs_cmid and k.time>time
)