title: Rails/AR find where habtm does not include
body: <p>I have a Rails app with Users, and each user HABTM Roles.</p>
  
  <p>I want to select Users without a specific role. I have searchlogic at my disposal, and I'm lost. I've tried using a combination of conditions and joins and includes and what not, but I can't seem to nail it. This works:</p>
  
  <pre><code>User.find(:all, :conditions =&gt; ['role_id != ?', Role[:admin].id], :joins =&gt; :roles)
  </code></pre>
  
  <p>To find users that are not admins, but doesn't not find users with no roles (which I want to find as well).</p>
  
  <p>What simple thing am I missing in my tired state?</p>