题解 | #浙大不同难度题目的正确率#

select
    qd.difficult_level difficult_level,
    count(qpd.result = 'right' or null)/count(1) correct_rate

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