The following example groups SalesQuota and aggregates SaleYTD amounts. The GROUPING function is applied to the SalesQuota column.
USE AdventureWorks;
GO
SELECT SalesQuota, SUM(SalesYTD) 'TotalSalesYTD', GROUPING(SalesQuota) AS 'Grouping'
FROM Sales.SalesPerson
GROUP BY SalesQuota WITH ROLLUP;
GO
The result set shows two null values under SalesQuota. The first NULL represents the group of null values from this column in the table. The second NULL is in the summary row added by the ROLLUP operation. The summary row shows the TotalSalesYTD amounts for all SalesQuota groups and is indicated by 1 in the Grouping column.
Here is the result set.
SalesQuota TotalSalesYTD Grouping
--------- ------------- --------
NULL 1533087.5999 0
250000.00 33461260.59 0
300000.00 9299677.9445 0
NULL 44294026.1344 1
(4 row(s) affected)