Ward Pond, one of the marvelous SQL geeks within Microsoft published a nice thing wich we had a discussion internally on concerning the capabilities of the IN operator:

http://blogs.technet.com/wardpond/archive/2009/09/04/database-programming-did-you-know-in-can-do-this.aspx

Were you aware of that ? :-)

Be also aware of the facts that NULL can change the expected results !

http://blogs.msdn.com/jenss/archive/2009/05/25/the-magic-about-trustable-relationships-with-null-and-not-in.aspx

-Jens