题解 | #浙大不同难度题目的正确率#
浙大不同难度题目的正确率
https://www.nowcoder.com/practice/d8a4f7b1ded04948b5435a45f03ead8c
/* 不同难度 考虑分组 GROUP BY difficult_level 浙江大学的情况 WHERE university = '浙江大学' 答题正确率 = 正确数/总数 */ SELECT difficult_level, SUM(CASE WHEN result='right'THEN 1 ELSE 0 END)/COUNT(qpd.question_id) AS correct_rate FROM question_practice_detail qpd LEFT JOIN user_profile up ON qpd.device_id = up.device_id LEFT JOIN question_detail qd ON qpd.question_id = qd.question_id WHERE up.university = '浙江大学' GROUP BY qd.difficult_level ORDER BY correct_rate ASC ;