今天以前的同学问我关于这方面的SQL语句,我特意记忆一下,毕竟这个也比较常见了
select * from (select * from member_payment
order by id desc) t group by member_id limit 10
[b]第一种是先排序,然后group,这样的话自然可以取到最适合的一条数据。
[/b]缺点很明显:Using temporary; Using filesort
select s.*
from (SELECT max(id) as id FROM `member_payment` group by `member_id` limit 10) t
left join `member_payment` as s on t.id=s.id
[b]第二种是联合查询
[/b]
select * from `member_payment` where EXISTS (
select `id` from (
SELECT max(`id`) as id FROM `member_payment` group by `member_id` limit 10) t
where t.`id`=`member_payment`.`id`
)
[b]第三种是子查询
[/b]窃以为第二种效率最高