MYSQL每个用户取1条记录的三种写法(group by xxx)
 
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
 
[sql] 
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
 
[sql] 
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
[sql] 
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