# 思路：
# 1、生成每个tag每个uid的最大分数、最小分数
# 2、利用row_number按照tag分组，按照最大分数、最小分数、uid排序生成排名
# 3、查询排名小于等于3的信息
select t2.tag,t2.uid,t2.rank_score from (
select t1.tag,t1.uid,
ROW_NUMBER() over(partition by t1.tag order by t1.max_score desc,t1.min_score desc,t1.uid desc) as rank_score 
from (
select e1.tag,e2.uid,max(e2.score) as max_score,min(e2.score) as min_score 
from exam_record as e2 left join examination_info as e1 on 
e2.exam_id=e1.exam_id group by e1.tag,e2.uid 
) t1 ) t2 
where t2.rank_score <= 3