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 u.university,q2.difficult_level,(count(q1.question_id)/count(distinct(q1.device_id))) as avg_answer from user_profile as u inner join question_practice_detail as q1 on u.device_id = q1.device_id inner join question_detail as q2 on q1.question_id=q2.question_id group by u.university, q2.difficult_level having u.university = "山东大学"