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))/sum(if(qpd.result is not null,1,0))
from question_practice_detail qpd 
     left join user_profile u on qpd.device_id = u.device_id
     left join question_detail qd on qpd.question_id = qd.question_id
where u.university='浙江大学'
group by 1
order by 2