关于MYSQL中每个用户取1条记录的三种写法(group by xxx)
作者：
本篇文章是对MYSQL中每个用户取1条记录的三种写法进行了详细的分析介绍，需要的朋友参考下
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
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。
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
第二种是联合查询
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`
)
第三种是子查询
窃以为第二种效率最高
复制代码 代码如下:
select * from (select * from member_payment
order by id desc) t group by member_id limit 10
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。
缺点很明显：Using temporary; Using filesort
复制代码 代码如下:
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
第二种是联合查询
复制代码 代码如下:
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`
)
第三种是子查询
窃以为第二种效率最高