題解 | #統(tǒng)計每個用戶的平均刷題數(shù)#
統(tǒng)計每個用戶的平均刷題數(shù)
http://fangfengwang8.cn/practice/f4714f7529404679b7f8909c96299ac4
select university, qd.difficult_level,
# 設(shè)備id是用戶數(shù)，注意去重
count(answer_cnt)/count(distinct up.device_id) avg_answer_cnt
from user_profile up
join question_practice_detail qpd
on up.device_id = qpd.device_id
join question_detail qd
on qd.question_id = qpd.question_id
where up.university = '山東大學'
# //這里排序兩個都要考慮
group by up.university, qd.difficult_level
