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 u.device_id, u.university, count(q.question_id) as question_cnt, sum( case when q.result = 'right' then 1 else 0 end ) as right_question_cnt FROM user_profile as u left JOIN question_practice_detail as q on u.device_id = q.device_id and month (q.date) = 8 where u.university = '复旦大学' group by u.device_id, u.university
原来还有sum case这个操作,
不要漏写了university里的s