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, qd.difficult_level, count(qpd.question_id)/count(distinct u.device_id) avg_answer_cnt from user_profile u left join question_practice_detail qpd on u.device_id =qpd.device_id join question_detail qd on qpd.question_id = qd.question_id group by u.university, qd.difficult_level