题解 | #获得积分最多的人(一)#

不用窗口函数，用limit+order by实现
select u.name,a.grade_num from (select user_id,sum(grade_num) grade_num
from grade_info 
group by user_id 
order by grade_num desc 
limit 1) a,user u
where a.user_id=u.id