select * from jiekuan

select * from jiekuan,(select cid,max(id) as id from jiekuan group by cid) as t2 where jiekuan.id=t2.id order by jiekuan.cid --正确

select * from jiekuan right join (select cid,max(id) as id from jiekuan group by cid) as t2 on jiekuan.id=t2.id order by jiekuan.cid --正确

select * from jiekuan left join (select cid,max(id) as id from jiekuan group by cid) as t2 on jiekuan.id=t2.id order by jiekuan.cid --多了