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
http://www.nowcoder.com/practice/88aa923a9a674253b861a8fa56bac8e5
from user_profile up right join question_practice_detail qpd
on up.device_id=qpd.device_id
group by university
order by university asc