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 university, difficult_level, count(q.question_id) /count(distinct q.device_id) as avg_answer_cnt from user_profile u join question_practice_detail q on u.device_id=q.device_id join question_detail d on q.question_id=d.question_id group by university ,difficult_level