题解 | #浙大不同难度题目的正确率#

select qd.difficult_level,sum(if(result='right',1,0))/count(result) as correct_rate
from question_practice_detail as qpd
join user_profile as up
on qpd.device_id =up.device_id and up.university='浙江大学'
join question_detail as qd
on qpd.question_id = qd.question_id
group by qd.difficult_level
order by correct_rate