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.question_id)/count(distinct qpd.device_id) avg_answer_cnt from user_profile up, question_practice_detail qpd, question_detail qd where up.device_id=qpd.device_id and qpd.question_id=qd.question_id and university = '山东大学' Group By difficult_level