with total_grade_info as (
    select
        user_id,
        sum(grade_num) as grade_num
    from 
        grade_info
    group by 
        user_id
)

select 
    u.name,
    t_g_i.grade_num
from 
    total_grade_info as t_g_i
left join
    user as u
on 
    t_g_i.user_id = u.id
order by 
    t_g_i.grade_num desc
limit 1