题解 | #获得积分最多的人(一)#

-- 解1:
select a.name, sum(b.grade_num ) as grade_num  from user   a left join grade_info b  on a.id=b.user_id group by a.name order by grade_num desc limit 1;
-- 解2
SELECT
	u.NAME,
	b.m
FROM
	USER u
	LEFT JOIN (
	SELECT
		user_id,
		m,
		rank() over ( ORDER BY m DESC ) AS t_rank 
	FROM
		( SELECT user_id, sum( grade_num ) AS m FROM grade_info GROUP BY user_id ) t 
	) AS b ON u.id = b.user_id 
	
WHERE
	b.t_rank = 1;