title: How do you check "if not null" with Eloquent?
body: <p>How do you check if a field <em>is not null</em> with Eloquent?</p>
  
  <p>I tried <code>Model::where('sent_at', 'IS NOT', DB::raw('null'))-&gt;...</code> but it gives <code>IS NOT</code> as a binding instead of a comparison.</p>
  
  <p>This is what <code>DB::getQueryLog()</code> says about it:</p>
  
  <pre><code>  'query' =&gt; string 'select * from my_table where sent_at = ? and profile_id in (?, ?) order by created_at desc' (length=101)
    'bindings' =&gt; 
      array (size=3)
        0 =&gt; string 'IS NOT' (length=6)
        1 =&gt; int 1
        2 =&gt; int 4
  </code></pre>