题解 | #统计复旦用户8月练题情况#

select a.device_id, a.university, count(b.question_id) as question_cnt, sum(if(b.result='right',1,0)) as right_question_cnt from ( select device_id, question_id, result from question_practice_detail where month(date)=8 ) b right join ( select device_id, university FROM user_profile WHERE university='复旦大学' ) a on a.device_id=b.device_id group by a.device_id