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, qd.difficult_level, count(qd.question_id)/count(distinct u.device_id) from question_practice_detail qpd left join user_profile u on qpd.device_id=u.device_id left join question_detail qd on qpd.question_id=qd.question_id where u.university="山东大学" group by qd.difficult_level
