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(qp.question_id)/count(distinct(qp.device_id)) as avg_answer_cnt from user_profile u, question_practice_detail qp, question_detail qd where u.device_id = qp.device_id and qp.question_id = qd.question_id and university = '山东大学' group by difficult_level;
