题解 | #浙大不同难度题目的正确率#

with f as (select qpd.device_id
                , qpd.question_id
                , qpd.result
                , qd.difficult_level
           from question_practice_detail qpd
                    inner join question_detail qd on qpd.question_id = qd.question_id)
select f.difficult_level
     , sum(if(f.result = 'right', 1, 0)) / count(result) as correct_rate
from user_profile up
         inner join f on up.device_id = f.device_id
where up.university = '浙江大学'
group by f.difficult_level
order by correct_rate;