题解 | #统计复旦用户8月练题情况#

select device_id,university,count(question_id) as question_cnt,
sum(res_r) as right_question_cnt
from (select a.device_id,university,result,date,question_id,
case when result='right' then 1 else 0 end as res_r,
case when result='wrong' then 1 else 0 end as res_w
from user_profile as a
left join question_practice_detail as b
on a.device_id=b.device_id
where (month(date) =8 and university='复旦大学')
or (month(date) is null and university='复旦大学')) as c 
group by university,device_id