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(question_id) / count(distinct (device_id)) as avg_answer_cnt
from
user_profile
inner join question_practice_detail using (device_id)
inner join question_detail using(question_id)
group by university,difficult_level
