SELECT Submission_Date
     , Submission_Count
     , BestHacker_Id
     , (SELECT Name
          FROM Hackers
         WHERE Hacker_Id = BestHacker_Id) Name
  FROM (SELECT Submission_Date
             , SUM(Submission_Count) Submission_Count
             , MIN(BestHacker_Id) BestHacker_Id
          FROM (SELECT Hacker_Id
                     , Submission_Date
                     , CASE WHEN MAX(Submission_No) OVER (PARTITION BY Submission_Date) = Submission_No
                         THEN Hacker_Id END BestHacker_Id
                     , CASE WHEN COUNT(*) OVER (PARTITION BY Hacker_Id ORDER BY Submission_Date) + DATE'2016-03-01' - 1 = Submission_Date 
                         THEN 1 ELSE 0 END Submission_Count
                  FROM (SELECT h.Hacker_Id
                             , s.Submission_Date
                             , COUNT(*) Submission_No
                          FROM Hackers h
                             , Submissions s
                         WHERE h.Hacker_Id = s.Hacker_Id
                         GROUP BY h.Hacker_Id
                             , s.Submission_Date))
         GROUP BY Submission_Date)
 ORDER BY Submission_Date;