title: How to get primary key name on laravel query builder
body: <p>Is there a way to get a table's primary key name using the Laravel query builder? Can i do something like </p>
  
  <pre><code>$key = DB::table($someTable)-&gt;getPrimaryKey();
  </code></pre>
  
  <p>I've looked through the documentation and API but couldn't find any reference to it.</p>
  
  <p>Thanks in advance. </p>