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(t2.question_id) / count(distinct t2.device_id) from user_profile t1, question_practice_detail t2, question_detail t3 where t1.device_id = t2.device_id and t2.question_id = t3.question_id and t1.university = '山东大学' group by t3.difficult_level
这里和前两个题目一样。
1.首先我们先将三张表连接起来from t1,t2,t3
2.然后选择山东大学的用户 where university = '山东大学'
3.然后在按照题目难度分组 group by difficult_level
4.最后在计算平均大题次数 count
