sql script

select u.id, u.name, tmp1.grade_sum
from (select user_id, rank() over(order by grade_sum desc) as g_rank, grade_sum
      from (select user_id, sum(grade_num) as grade_sum
            from grade_info
            group by user_id) tmp) tmp1, `user` u
where tmp1.user_id=u.id
and tmp1.g_rank=1