title: Argument data type uniqueidentifier is invalid for argument 1 of substring function
body: <p>I am trying to get the first part of a Guid Field with the TSQL substring function as follows</p>
  
  <pre><code>SELECT SUBSTRING(Guid, 1, 8) AS Gu FROM MyTable
  </code></pre>
  
  <p>but all i get is this error.</p>
  
  <p><em>Argument data type uniqueidentifier is invalid for argument 1 of substring function.</em></p>
  
  <p>So what is going on here? Should i treat the Guid as pure string first or...?</p>
  
  <p>Thanks in advance!</p>