SELECT runtime  ---internalDowntime-OtherDowntime AS productiontime  based on overlapping
FROM
(
    SELECT deck.ID_DECKUNGSBEITRAG,
           DATEDIFF(MINUTE, l.START_DATUM, l.END_DATUM) / 60.0 runtime, --which includes downtime,
    (
        SELECT SUM(DATEDIFF(MINUTE, le.START_DATUM, le.END_DATUM) / 60.0)
        FROM dbo.STILLSTANDSZEIT s
             INNER JOIN dbo.LEITSTAND le ON le.ID_STILLSTANDSZEIT = s.ID_STILLSTANDSZEIT
        WHERE s.ID_HERSTELLVORSCHRIFT = hs.ID_HERSTELLVORSCHRIFT
    ) internalDowntime,
    (
        SELECT SUM(DATEDIFF(MINUTE, ZEIT_VON, ZEIT_BIS) / 60.0)
        FROM dbo.PRODUKTIONSANLAGE_AUSFALLZEIT
        WHERE ZEIT_VON >= l.START_DATUM
              AND ZEIT_VON <= l.END_DATUM
              AND ID_PRODUKTIONSANLAGE = p.ID_PRODUKTIONSANLAGE
    ) OtherDowntime
    FROM dbo.DECKUNGSBEITRAG deck
         INNER JOIN dbo.HERSTELLVORSCHRIFT hs ON deck.CHARGE = hs.CHARGE_NUMMER
         INNER JOIN dbo.LEITSTAND l ON l.ID_HERSTELLVORSCHRIFT = hs.ID_HERSTELLVORSCHRIFT
         INNER JOIN dbo.PRODUKTIONSANLAGE p ON p.ID_PRODUKTIONSANLAGE = l.ID_PRODUKTIONSANLAGE
    WHERE deck.CHARGE = 'CHG0116112945'
          AND deck.ID_MANDANT = 1
) temp;

SELECT DATEDIFF(minute,'2016-12-09 01:00:49.203','2016-12-12 22:30:04.787')/60.0       =  93.500000

SELECT DATEDIFF(minute,'2016-12-10 06:00:00.000','2016-12-12 06:00:00.000')/60.0  =48.000000