注意时间条件 select up.device_id,up.university, count(qpd.question_id) as "question_cnt", sum(case when qpd.result="right" then 1 else 0 end) as "right_question_cnt" from user_profile up left join question_practice_detail qpd on up.device_id = qpd.device_id where up.university = "复旦大学" and (month(qpd.dat...