题解 | #每类试卷得分前3名#

```select 
*
from
    (
        select 
            tag,uid,
            row_number()over(partition by tag order by  dd desc, xx desc,uid desc ) ranking
        from 
            (
                select 
                   tag,uid,
                    max(score) dd, --
                    min(score)  xx --
                from exam_record 
                join examination_info 
                on exam_record.exam_id=examination_info.exam_id
                group by tag,uid
            ) t1 -- ①求出每个人在每类试卷中的最大最小值
    )t2 --  ②按照要求进行排序
where ranking<=3 -- ③去前三