title: How to use the "exists" function of Squeryl?
body: <p>I found there is a <code>exists</code> function in the document of <a href="http://squeryl.org/functions.html" rel="nofollow">Squeryl</a>, but I can't find an example of how to use it.</p>
  
  <p>Would someone give me an example of "exists"?</p>