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 a.university, c.difficult_level , (count(qpd.question_id) / (count(distinct qpd.device_id))) avg_answer_cnt from user_profile a left join question_practice_detail qpd on a.device_id = qpd.device_id left join question_detail c on qpd.question_id = c.question_id where c.question_id is not null group by a.university , c.difficult_level