text: SELECT H.HACKER_ID, H.NAME, SUM(S.SCORE)
    FROM HACKERS H, (SELECT HACKER_ID, CHALLENGE_ID, MAX(SCORE) AS SCORE
                       FROM SUBMISSIONS
                      GROUP BY HACKER_ID, CHALLENGE_ID) AS S
   WHERE H.HACKER_ID = S.HACKER_ID
   GROUP BY H.HACKER_ID, H.NAME
   HAVING SUM(S.SCORE) <> 0
    ORDER BY 3 DESC, 1;
  
  ---------------------------------
  
  WITH MAX_SCORE AS (
      SELECT HACKER_ID, CHALLENGE_ID, MAX(SCORE)
        FROM SUBIMISSIONS
       GROUP BY HACKER_ID, CHALLENGE_ID 
  )
  SELECT M.HACKER_ID, H.NAME, SUM(M.SCORE)
    FROM MAX_SCORE M INNER JOIN HACKERS H ON M.HACKER_ID = H.HACKER_ID
   GROUP BY M.HACKER_ID, H.NAME
  HAVING M.SCORE > 0;