题解 | 浙大不同难度题目的正确率

SELECT
    qd.difficult_level,
    SUM(
        CASE
            WHEN qpd.result = 'right' THEN 1
            ELSE 0
        END
    ) / COUNT(*) AS correct_rate
FROM
    question_detail AS qd
    JOIN question_practice_detail AS qpd ON qd.question_id = qpd.question_id
    JOIN user_profile AS up ON qpd.device_id = up.device_id
WHERE up.university = '浙江大学'
GROUP BY
    qd.difficult_level
ORDER BY 
	correct_rate ASC 

两个月没碰SQL了，最近课程在学习，并且开始准备实习面试了，计划开始复健。

不得不说这东西就是一小段时间不碰就忘光光，这种超级无敌简单难度的题竟然半个小时才调好，真忘干净了吧0.0