题解 | #统计每个学校各难度的用户平均刷题数#
统计每个学校各难度的用户平均刷题数
https://www.nowcoder.com/practice/5400df085a034f88b2e17941ab338ee8
select u.university,q.difficult_level,count(q.difficult_level)/count(distinct p.device_id) avg_answer_cnt from user_profile u inner join question_practice_detail p on u.device_id=p.device_id left join question_detail q on p.question_id = q.question_id group by difficult_level,university order by university,difficult_level
