SELECT id,name ,t FROM user u RIGHT JOIN (SELECT user_id,SUM(grade_num) OVER (PARTITION BY user_id) t FROM grade_info ORDER BY t DESC ) a ON u.id = a.user_id GROUP BY id HAVING t=(SELECT SUM(grade_num) c FROM grade_info GROUP BY user_id ORDER BY c DESC LIMIT 1) ORDER BY t DESC

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SELECT id,NAME,t FROM user u RIGHT JOIN ( SELECT DISTINCT(user_id),t,RANK() OVER (ORDER BY t DESC) r FROM (SELECT user_id, SUM(grade_num) OVER (PARTITION BY user_id) t FROM grade_info) a) b ON u.id=b.user_id WHERE r=1