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Looking at the <code>add_aggregate</code> function within <code>django/db/models/sql/query.py</code>, query objects will not be accepted as input values. Unfortunately, there is currently no direct way within Django to aggregate/annotate on what amounts to a queryset, especially not one that is additionally filtered somehow. Assuming the following models: <pre><code>class Item(models.Model): name = models.CharField(max_length=32) class Tag(models.Model): itemfk = models.ForeignKey(Item, related_name='tags') name = models.CharField(max_length=32) class FavoritedTag(models.Model): user = models.ForeignKey(User) tag = models.ForeignKey(Tag) </code></pre> Also, you cannot annotate a queryset on fields defined via <code>.extra()</code>. One could drop into SQL in <code>views.py</code> like so: <pre><code>from testing.models import Item, Tag, FavoritedTag from django.shortcuts import render_to_response from django.contrib.auth.decorators import login_required from django.utils.datastructures import SortedDict @login_required def interest_level(request): ruid = request.user.id qs = Item.objects.extra( select = SortedDict([ ('interest_level', 'SELECT COUNT(*) FROM testing_favoritedtag, testing_tag \ WHERE testing_favoritedtag.user_id = %s \ AND testing_favoritedtag.tag_id = testing_tag.id \ AND testing_tag.itemfk_id = testing_item.id'), ]), select_params = (str(ruid),) ) return render_to_response('testing/interest_level.html', {'qs': qs}) </code></pre> Template: <pre><code>{% for item in qs %} name: {{ item.name }}, level: {{ item.interest_level }} {% endfor %} </code></pre> I tested this using MySQL5. Since I'm no SQL expert though, I'd be curious as to how to optimize here, or if there is another way to "lessen" the amount of SQL. Maybe there is some interesting way to utilize the <code>related_name</code> feature here directly within SQL?
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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