题解 | #作答试卷得分大于过80的人的用户等级分布#
作答试卷得分大于过80的人的用户等级分布
http://www.nowcoder.com/practice/5bc77e3a3c374ad6a92798f0ead4c744
嵌套子查询，题目没有说清楚，后面level个数相同时用level进行排序
select level,count(distinct uid) as level_cnt from user_info
where uid in (select uid from user_info where uid in
(select distinct uid from exam_record where exam_id in
(select exam_id from examination_info where tag='SQL') and score >80))
group by level
order by level_cnt desc ,level desc
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