测试的几条SQL语句,group by,left join

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
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原文地址《测试的几条SQL语句,group by,left join
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