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

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

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

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.

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