title: When to use EXCEPT as opposed to NOT EXISTS in Transact SQL?
body: <p>I just recently learned of the existence of the new &quot;EXCEPT&quot; clause in SQL Server (a bit late, I know...) through reading code written by a co-worker. It truly amazed me!</p>
  <p>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 &quot;AND NOT EXISTS...&quot;?</p>
  <p>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 &quot;AND NOT EXISTS&quot; 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?</p>
  <p>So I'd like to know: what are the guidelines for using this powerful tool?</p>