题解 | #浙大不同难度题目的正确率#

select case when difficult_level='easy' then 'easy' when difficult_level='medium' then 'medium' when difficult_level='hard' then 'hard' end as "difficult_level",sum(if(qpd.result='right',1,0))/count(*) "correct_rate" from user_profile up join question_practice_detail qpd on up.device_id = qpd.device_id join question_detail qd on qpd.question_id = qd.question_id where university = '浙江大学' group by difficult_level order by correct_rate asc;