题解 | #浙大不同难度题目的正确率#

就这？就这？3分钟不能再多了

select
    difficult_level,
    count(if(p.result = 'right',1,NULL)) / count(p.result) correct_rate
FROM
    question_practice_detail p
JOIN(
    SELECT
        university,device_id
    from user_profile
    WHERE university= '浙江大学'
) u 
ON u.device_id = p.device_id
JOIN question_detail d
ON d.question_id = p.question_id
GROUP BY
difficult_level
ORDER BY
correct_rate