SQL Server 2008 - MERGE Operator

MERGE Operator
Use GROUPING SETS to obtain results similar to those generated by using CUBE and ROLLUP, however GROUPING SETS is more flexible, offers better performance, and is ANSI SQL 2006 compliant. GROUPING SETS enables the GROUP BY clause to generate multiple grouped aggregations in a single result set. It is equivalent to using UNION ALL to return a result set from multiple SELECT statements, each of which has a GROUP BY clause.