title: what does EXEC master.. Do?
body: <p>I have seen this like:</p>
  
  <pre><code>EXEC master.dbo.xp_cmdshell
  </code></pre>
  
  <p>What does <code>master</code> refer to?</p>
  
  <p><strong>Update</strong><br>
  And why sometimes is followed by two points:   </p>
  
  <pre><code> master..
  </code></pre>
  
  <p>generally we would use <code>master.dbo.</code>  Am I correct, so why some people write <code>master..</code>?</p>