title: Union on ValuesQuerySet in django
body: <p>I've been searching for a way to take the union of querysets in django. From what I read you can use query1 | query2 to take the union... This doesn't seem to work when using values() though. I'd skip using values until after taking the union but I need to use annotate to take the sum of a field and filter on it and since there's no way to do "group by" I have to use values(). The other suggestions I read were to use Q objects but I can't think of a way that would work.</p>
  
  <p>Do I pretty much need to just use straight SQL or is there a django way of doing this?</p>
  
  <p>What I want is:</p>
  
  <pre><code>q1 = mymodel.objects.filter(date__lt = '2010-06-11').values('field1','field2').annotate(volsum=Sum('volume')).exclude(volsum=0)
  q2 = mymodel.objects.values('field1','field2').annotate(volsum=Sum('volume')).exclude(volsum=0)
  query = q1|q2
  </code></pre>
  
  <p>But this doesn't work and as far as I know I need the "values" part because there's no other way for Sum to know how to act since it's a 15 column table.</p>