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