title: Django Annotate not working on some cases
body: <p>I have a Django queryset with annotation that works well doing a count over year/month, but for some reason THE SAME CODE for another model does not work.</p>
  <p>Code that works:</p>
  <pre><code>usages = Usage.objects.all()
  usages = usages.annotate(year=ExtractYear('usage_datetime'),
                              month = ExtractMonth('usage_datetime')).values('year','month').annotate(total=Count('id'))
  </code></pre>
  <p>Code that dont work (only calculates 1 on the count):</p>
  <pre><code>events = Event.objects.all()
  events = events.annotate(year=ExtractYear('created'),
                              month = ExtractMonth('created')).values('year','month').annotate(total=Count('id'))
  </code></pre>
  <p>The first one outputs:</p>
  <blockquote>
  <p>&lt;QuerySet [{'year': 2020, 'month': 9, 'total': 13}, {'year': 2020,
  'month': 8, 'total': 18}, {'year': 2020, 'month': 7, 'total': 29},
  {'year': 2020, 'month': 6, 'total': 31},</p>
  </blockquote>
  <p>The second one:</p>
  <blockquote>
  <p>&lt;QuerySet [{'year': 2020, 'month': 8, 'total': 1}, {'year': 2020,
  'month': 8, 'total': 1}, {'year': 2020, 'month': 8, 'total': 1},
  {'year': 2020, 'month': 8, 'total': 1}
  'total': 1}, '...(remaining elements truncated)...']&gt;</p>
  </blockquote>
  <p>The second one is not counting like the first one.... not sure what it may be....
  Since the only difference is on the model, I would assume thats the issue, so here are my models:</p>
  <p><strong>models.py</strong></p>
  <pre><code>class Event(models.Model):
      name = models.CharField(max_length=255)
      created = models.DateTimeField(auto_now_add=True, editable=False)
      last_updated = models.DateTimeField(auto_now=True, editable=False)
      
      class Meta:
          ordering = ('-created',)
  
  class Usage(models.Model):
      name = models.CharField(max_length=255)
      usage_datetime = models.DateTimeField(auto_now_add=True)
  </code></pre>
  <h2><strong>EDIT</strong>
  Here is the query the Events are performing</h2>
  <pre><code>SELECT django_datetime_extract('year', &quot;EventTracker_event&quot;.&quot;created&quot;, 'UTC') AS &quot;year&quot;, 
         django_datetime_extract('month', &quot;EventTracker_event&quot;.&quot;created&quot;, 'UTC') AS &quot;month&quot;, 
         COUNT(&quot;EventTracker_event&quot;.&quot;id&quot;) AS &quot;total&quot; 
    FROM &quot;EventTracker_event&quot; 
   GROUP BY django_datetime_extract('year', &quot;EventTracker_event&quot;.&quot;created&quot;, 'UTC'), 
         django_datetime_extract('month', &quot;EventTracker_event&quot;.&quot;created&quot;, 'UTC'), 
         &quot;EventTracker_event&quot;.&quot;created&quot; 
   ORDER BY &quot;EventTracker_event&quot;.&quot;created&quot; DESC
  </code></pre>
  <p>The created for some reason is making its way on the group by....</p>