题解 | #浙大不同难度题目的正确率#

select
    c.difficult_level,
    sum(
        case
            when b.result = "right" then 1
            else 0
        end
    ) / count(1) as correct_rate
from
    user_profile a
    join question_practice_detail b on a.device_id = b.device_id
    and a.university = "浙江大学"
    join question_detail c on b.question_id = c.question_id
group by
    c.difficult_level
order by
    correct_rate asc

这个题正确率不应该这么低啊