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,d.difficult_level, count(p.question_id)/count(distinct p.device_id) as avg_answer_cnt from user_profile u join question_practice_detail p on u.device_id=p.device_id join question_detail d on p.question_id=d.question_id group by u.university,d.difficult_level
分组的多表联查结果，难度不大
