title: Why is this django annotated queryset with rawSQL values not set but raw query returns results?
body: <p>The problem I have is the django queryset does not contain the data from raw sql query</p>
  <pre><code>interfaces = Interface.objects.filter(
      membership__in=membership_set
  ).annotate(
      utilisation=RawSQL(
          'SELECT utilisation FROM interfacestat WHERE interface.name = interfacestat.ifl AND interfacestat.date = &quot;%s&quot;'
          ,(recent_date,)
      ),
  ).order_by('name')
  </code></pre>
  <p>So I am using a <code>RawSQL</code> expression to populate the <code>utilisation</code> field.</p>
  <p>I check the raw sql with <code>print(interfaces.query)</code> and run that directly on MySQL.
  It returns results for the <code>utilisation</code> field on a few records - however when I loop through the queryset the <code>utilisation</code> field is always unset (None).</p>
  <p>eg.</p>
  <pre><code>interfaces[0].__dict__
  {'_state': &lt;django.db.models.base.ModelState object at 0x109b1fdf0&gt;, 'id': 230083, 'name': 'ae1.3216', ...'utilisation': None}
  </code></pre>
  <p>Looping through:</p>
  <pre><code>ipdb&gt; all = interfaces.values()
  ipdb&gt; for item in all:
      print(item.get('utilisation'))
   
  None
  None
  None
  None
  None
  None
  None
  None
  None
  None
  None
  None
  None
  </code></pre>