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
    user_profile up
    left join question_practice_detail qpd on up.device_id = qpd.device_id
    inner join question_detail qd on qpd.question_id = qd.question_id
where
    up.university = '浙江大学'
group by
    qd.difficult_level order by correct_rate asc;