题解 | #统计每个用户的平均刷题数#
统计每个用户的平均刷题数
https://www.nowcoder.com/practice/f4714f7529404679b7f8909c96299ac4
select "山东大学" as university, B.difficult_level, count(*)/count(distinct A.device_id) from question_practice_detail as A inner join question_detail as B on A.question_id=B.question_id and A.device_id in (select device_id from user_profile where university="山东大学") group by B.difficult_level