select
    ID
    ,DIFF
from
    (
    select
        member_id as ID
        ,(score1 - score2) as DIFF
        ,ABS(score1 - score2)  as diff_abs
    from
        contest_results
    )
where
    --diff_abs >= 20
    DIFF >= 20
order by 
    DIFF desc
    ,ID desc