题解 | #浙大不同难度题目的正确率#

select
  t3.difficult_level,
  SUM(IF(t1.result = "right", 1, 0)) / COUNT(t3.difficult_level) as correct_rate
from
  question_practice_detail as t1
  left join user_profile as t2 on t1.device_id = t2.device_id
  right join question_detail as t3 on t1.question_id = t3.question_id
where
  t2.university = "浙江大学"
group by
  t3.difficult_level
order by
  correct_rate asc