题解 | #浙大不同难度题目的正确率#

select
    q2.difficult_level,
    sum(if (q1.result = 'right', 1, 0)) / count(q1.result)
from
    user_profile u
    join question_practice_detail q1 on u.device_id = q1.device_id
    join question_detail q2 on q1.question_id = q2.question_id
where
    u.university = '浙江大学'
group by
    q2.difficult_level
order by
    sum(if (q1.result = 'right', 1, 0)) / count(q1.result)