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