SQL Server 2008 provides several operators that provide you with the ability to combine or compare the results from multiple SELECT statements. The UNION operator has been available from the first version of SQL Server to provide the ability to combine the result sets from multiple queries. On the other hand, the EXCEPT and INTERSECT operators were introduced in SQL Server 2005 to provide the ability to compare the results from two queries and provide a new result set based on whether or not there are rows in common between the result sets.

In addition, datasets can be manipulated by using the APPLY operator to apply a table-valued function against each row of the query results from what is defined as the outer table.