题解 | 浙大不同难度题目的正确率

select difficult_level, fenzi/fenmu as correct_rate
from(
 select difficult_level,count(qpd.id) over (partition by   difficult_level) as fenmu,
 count(if(qpd.result='right',1,null)) over (partition by  difficult_level) as fenzi,
 row_number() over (partition by difficult_level) as rn
 from question_practice_detail qpd 
 join question_detail qd on qpd.question_id=qd.question_id
 join user_profile up on qpd.device_id=up.device_id
 where university='浙江大学') as zheda
 where rn=1
 order by correct_rate