题解 | #统计每个学校各难度的用户平均刷题数#
统计每个学校各难度的用户平均刷题数
https://www.nowcoder.com/practice/5400df085a034f88b2e17941ab338ee8
select university,difficult_level,
count(qpd.question_id)/count(distinct qpd.device_id) as avg_answer_cnt
from question_detail as qd
inner join question_practice_detail as qpd
on qd.question_id=qpd.question_id
inner join user_profile as up
on qpd.device_id=up.device_id
group by university,difficult_level
