Good Explanantion and usage examples of the Except and Intersect  Operators in SQL 2005 ( 2008).

From decipherinfosys
In SQL Server 2005, MSFT introduced two new operators in their T-SQL language: Except and Intersect. We had briefly touched upon these while discussing the MERGE command in Oracle – you can read more on that post here. EXCEPT returns the distinct data value from the left query (query on left side of the operand) which does not exist in the right query (query on the right side of the operand). INTERSECT returns data value which is common in both queries. In Oracle, the equivalent of the EXCEPT operator is MINUS and INTERSECT is same as INTERSECT. In SQL 2005, using EXCEPT and INTERSECT, one can also simulate the MERGE command in Oracle (see the blog post that is mentioned above).

Read Full Post Here