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
us.university,
qd.difficult_level,
count(qu.result)/count(distinct(qu.device_id)) as avg_answer_cnt
from
question_practice_detail as qu
left join
user_profile as us
on qu.device_id = us.device_id
left join
question_detail as qd
on qu.question_id = qd.question_id
group by
qd.difficult_level,
us.university
having
us.university = "山东大学";

