题解 | 浙大不同难度题目的正确率

select
    difficult_level,
    sum(
        case
            when result = 'right' then 1
            else 0
        end
    ) / count(result) correct_rate
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
    university = '浙江大学'
group by
    difficult_level
order by
    correct_rate