题解 | #获得积分最多的人(三)#

select
    u.id,
    u.name,
    sum(if (g.type = 'add', g.grade_num, - g.grade_num)) as grade_num
from
    user u
    left join grade_info g on u.id = g.user_id
group by
    u.id,
    u.name
having
    grade_num = (
        select
            max(grade_num)
        from
            (
                select
                    u.id,
                    sum(if (g.type = 'add', g.grade_num, - g.grade_num)) as grade_num
                from
                    user u
                    left join grade_info g on u.id = g.user_id
                group by
                    u.id
            ) t
    )
order by
    grade_num desc,
    id;