title: Query builder select entity relation id
body: <p>I have some query and I need in select block select id relation entity, how can I do it without some join, like in SQL? In example I add leftJoin but I want understand it's possible without join like <code>lsc.serviceCompany.id</code> or how ? </p>
  
  <pre><code>        $qb
          -&gt;select('
              ser_com.id as serviceCompanyId 
          ')
          -&gt;from('AppBundle:LocationServiceCompany', 'lsc')
          -&gt;leftJoin('lsc.serviceCompany', 'ser_com')
          -&gt;where('lsc.serviceCompany = :sc')
          -&gt;setParameter('sc', $serviceCompany);
  </code></pre>