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(t1.device_id)/count(distinct t1.device_id) as avg_answer_cnt
from question_practice_detail as t1
left join(
select
device_id,
university
from user_profile
) as t2
on t1.device_id = t2.device_id
where t1.device_id is not null
group by university;
