题解 | 统计每个学校的答过题的用户的平均答题数
统计每个学校的答过题的用户的平均答题数
https://www.nowcoder.com/practice/88aa923a9a674253b861a8fa56bac8e5
select u.university,
round(count(q.device_id)/count(distinct(u.device_id)),4) as avg_answer_cnt
from user_profile u, question_practice_detail q
where u.device_id = q.device_id
group by u.university
order by u.university;
还是感觉很诡异…
论distinct的用法了属于是…