You're not using WITH ROLLUP correctly. WTIH ROLLUP creates a subtotal and/or total based upon what you tell it. You didn't specify what to call the subtotal and/or total so it is calling it NULL.
This query generates a subtotal report:
SELECT CASE WHEN (GROUPING(Item) = 1) THEN 'ALL'
ELSE ISNULL(Item, 'UNKNOWN')
END AS Item,
CASE WHEN (GROUPING(Color) = 1) THEN 'ALL'
ELSE ISNULL(Color, 'UNKNOWN')
END AS Color,
SUM(Quantity) AS QtySum
FROM Inventory
GROUP BY Item, Color WITH ROLLUP
Output:
Item Color QtySum
-------------------- -------------------- --------------------------
Chair Blue 101.00
Chair Red 210.00
Chair ALL 311.00
Table Blue 124.00
Table Red 223.00
Table ALL 347.00
ALL ALL 658.00
