select CON1.MEMBER_ID as ID ,(CON1.SCORE1 - CON2.SCORE2) as DIFF
from CONTEST_RESULTS as CON1
inner join CONTEST_RESULTS as CON2
on CON1.MEMBER_ID = CON2.MEMBER_ID
where (DIFF >= 20) or (DIFF <= -20)
order by DIFF desc, ID asc;