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(b.result) correct_rate from user_profile a inner join question_practice_detail b on a.device_id=b.device_id inner join question_detail c on b.question_id=c.question_id where a.university='浙江大学' group by c.difficult_level order by correct_rate asc;