select
  MEMBER_ID as "ID"
 ,(SCORE1 - SCORE2) as "DIFF"
from
 CONTEST_RESULTS
where
 MEMBER_ID
in
 (
  select
   MEMBER_ID
  from
   CONTEST_RESULTS
  where
   (SCORE1 - SCORE2) >= 20 or (SCORE1 - SCORE2) <= -20
 )
order by
 "DIFF" desc, "ID" desc
;