题解 | 浙大不同难度题目的正确率

select qd.difficult_level,(sum(if(qpd.result='right',1,0))/count(qpd.question_id)) as correct_rate
from question_practice_detail as qpd

inner join user_profile as up
on qpd.device_id=up.device_id and up.university='浙江大学'

inner join question_detail as qd
on qpd.question_id=qd.question_id

group by qd.difficult_level
order by correct_rate asc