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
select difficult_level, sum(right_answ_num) / sum(answ_num) as correct_rate from ( select a.device_id, b.question_id, d.difficult_level, coalesce(b.answ_num, 0) as answ_num, coalesce(c.right_answ_num, 0) as right_answ_num from ( select device_id from user_profile where university = '浙江大学' group by 1 ) a left join ( select device_id, question_id, count(question_id) as answ_num from question_practice_detail group by 1, 2 ) b on a.device_id = b.device_id left join ( select device_id, question_id, count(question_id) as right_answ_num from question_practice_detail where result = 'right' group by 1, 2 ) c on a.device_id = c.device_id and b.question_id = c.question_id left join ( select question_id, difficult_level from question_detail ) d on b.question_id = d.question_id ) t1 where difficult_level is not null group by 1 order by 2 asc