WITH TBL1 AS ( -- all hacker_id who made at least one submission each day
    SELECT DISTINCT
        submission_date
        ,hacker_id
    From Submissions Sub
    WHERE hacker_id IN (
        SELECT DISTINCT hacker_id 
        FROM Submissions 
        WHERE submission_date <= Sub.submission_date
        GROUP BY hacker_id
        HAVING COUNT(DISTINCT submission_date) = (
            SELECT COUNT(DISTINCT submission_date)
            FROM Submissions
            WHERE submission_date <= Sub.submission_date
        )
    )
)
,TBL2 AS ( --no of unique hacker_id who made at least one submission each day
    SELECT
        submission_date
        ,COUNT(hacker_id) AS hackerNr
    From TBL1
    GROUP BY submission_date
)
,TBL3 AS ( -- number of submissions made by hacker each day
    SELECT 
        hacker_id
        ,submission_date
        ,COUNT(submission_id) AS nrSub 
    FROM Submissions 
    GROUP BY hacker_id, submission_date
)
,TBL4 AS ( -- lowest hacker_id each day
    SELECT DISTINCT
        T1.submission_date
        ,T2.hackerNr
        ,MIN(T3.hacker_id) AS hackerID
    FROM TBL1 T1
    LEFT JOIN TBL2 T2 ON T1.submission_date = T2.submission_date
    LEFT JOIN TBL3 T3 ON T1.submission_date = T3.submission_date
    WHERE T3.nrSub = (SELECT MAX(nrSub) FROM TBL3 WHERE submission_date = T1.submission_date GROUP BY submission_date)
    GROUP BY T1.submission_date, T2.hackerNr
)
SELECT 
    TBL4.*
    ,H.name
FROM TBL4
LEFT JOIN Hackers H ON H.hacker_id = TBL4.hackerID
ORDER BY TBL4.submission_date