GROUPING SETS

A GROUP BY clause that uses GROUPING SETS can generate a result set equvalent to that generated by a UNION ALL of multiple simple GROUP BY clauses.

SELECT TestName, year, SUM(TestSales)FROM TestTable

GROUP BY GROUPING SETS ((TestName), (TestYear))

The results will be the same as:

SELECT NULL as TestName, TestYear, SUM(TestSales)FROM TestTable GROUP BY TestYear

UNION ALL

SELECT TestName, NULL as TestYear, SUM(TestSales)FROM TestTable GROUP BY TestName

http://msdn.microsoft.com/en-us/library/bb510427.aspx