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
#指定条件 学校=山东大学 不同难度=以难度分组 平均答题数=总答题数/去重复做题人数
select up.university,qd.difficult_level,
round(count(qpd.question_id) / count(distinct qpd.device_id),4) as "平均答题数"
from question_practice_detail as qpd
left join user_profile as up on up.device_id = qpd.device_id
left join question_detail as qd on qd.question_id = qpd.question_id
where university = "山东大学"
group by up.university,qd.difficult_level
