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(t2.question_id) / count(distinct (t2.device_id)) as avg_answer_cnt
from
user_profile as t1,
question_practice_detail as t2,
question_detail as t3
where
t1.device_id = t2.device_id
and t2.question_id = t3.question_id
group by
university,
difficult_level
