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 up.device_id ,university ,count(question_id) as question_cnt ,count(if(result = 'right',1,null)) as right_question_cnt from user_profile as up left join question_practice_detail as qpd on up.device_id = qpd.device_id and month(date) = 8 where university = '复旦大学' group by up.device_id
第二种算正确题总数法：count(if(result='right',1,null))。sum是求和，count是统计非空个数。
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