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
http://www.nowcoder.com/practice/5400df085a034f88b2e17941ab338ee8
select
up.university,
qd.difficult_level,
count(qpd.question_id)/count(distinct up.device_id) #注意，问题数量可有重复，但设备（即用户）不能重复
from
user_profile as up
inner join
question_practice_detail as qpd on up.device_id = qpd.device_id
inner join
question_detail as qd on qpd.question_id = qd.question_id
group by up.university , qd.difficult_level
order by up.university asc
投递华为等公司10个岗位 >