title: SQL LEFT JOIN where clause with IN comparison
body: <p>May have inadvertently stumbled onto a good SQL test question.</p>
  
  <ul>
  <li>I have a table with let's say ~100 usernames.</li>
  <li>I have a set of 10 possible usernames { aname, bname, cname, dname, ... }</li>
  </ul>
  
  <p>If I do:</p>
  
  <pre><code>SELECT user.username FROM user WHERE user.username IN ('aname', 'bname', 'cname',...);
  </code></pre>
  
  <p>I get a list of usernames selected for, minus the ones not found in the table, grand.</p>
  
  <p>What I actually want, is a list of the ones NOT found in the table.</p>
  
  <p>If the <code>WHERE...IN</code> clause list was a table, I'd just <code>LEFT JOIN</code> it onto the user table and filter for <code>NULLs</code>.</p>
  
  <p>Is there a way to do this without making a temp table and left joining that to the user table? I guess, sort of a left join of the user table to the <code>WHERE...IN</code> clause?</p>
  
  <p>I've never done or seen it, but perhaps it exists. </p>