题解 | #统计复旦用户8月练题情况#
统计复旦用户8月练题情况
https://www.nowcoder.com/practice/53235096538a456b9220fce120c062b3
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