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(question_id) / count(distinct (device_id)) as avg_answer_cnt from user_profile inner join question_practice_detail using (device_id) inner join question_detail using(question_id) group by university,difficult_level