I just recently learned of the existence of the new "EXCEPT" clause in SQL Server (a bit late, I know...) through reading code written by a co-worker. It truly amazed me!
But then I have some questions regarding its usage: when is it recommended to be employed? Is there a difference, performance-wise, between using it versus a correlated query employing "AND NOT EXISTS..."?
After reading EXCEPT's article in the BOL I thought it was just a shorthand for the second option, but was surprised when I rewrote a couple queries using it (so they had the "AND NOT EXISTS" syntax much more familiar to me) and then checked the execution plans - surprise! The EXCEPT version had a shorter execution plan, and executed faster, also. Is this always so?
So I'd like to know: what are the guidelines for using this powerful tool?