title: Why doesn't COUNT(DISTINCT (*)) work?
body: <p>I am still surprised why such simple query is not working:</p>
  
  <pre><code>SELECT COUNT(DISTINCT *) FROM dbo.t_test     
  </code></pre>
  
  <p>Where as </p>
  
  <pre><code>SELECT COUNT(DISTINCT col1) FROM dbo.t_test
  </code></pre>
  
  <p>and</p>
  
  <pre><code>SELECT DISTINCT * FROM dbo.t_test 
  </code></pre>
  
  <p>works.</p>
  
  <p>What is the alternative?</p>
  
  <p>EDIT:</p>
  
  <p><code>DISTINCT *</code> checks for uniqueness for the combined key of (col1,col2,...) and returns those rows. I expected COUNT(DISTINCT *) to just return number of such rows. Am I missing anything here?</p>