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 university,
count(question_id)/count(distinct t1.device_id) as avg_answer_cnt
from user_profile t1 join question_practice_detail t2
on t1.device_id = t2.device_id
group by university
order by university;
count()聚合函数计数；
distinct 前缀去重；
from...join...on...表连接；
group by分组；
order by排序。
