Getting the aggregate sum of a field from the other model in Listview

Question

I have the following two models:

models.py

class Model_Item(models.Model):
    item_name = models.CharField(max_length = 100, null = False, blank = False, unique = True)

    def __unicode__(self):
        return self.item_name

class Model_ItemTransaction(models.Model):
    item = models.ForeignKey(Model_Item, to_field = "item_name")
    item_sold = models.FloatField(null = True, blank = True)

    def __unicode__(self):
        return self.item

With this listview:

views.py

class View_Item(ListView):
    def get_queryset(self):
        queryset = Model_Item.objects.all()
        queryset = queryset.annotate(
                sum_ = Sum(When(model_itemtransaction__item_sold))
            )
        return queryset

And my goal is to get the total value of "item_sold" for each item, and display this value on Listview. How can I make this work?

I have been looking at the conditional expression and this stackoverflow post, but to no avail.

You never specify *what* to sum up, only *when* to sum up. – Willem Van Onsem May 14 '18 at 13:58 — Willem Van Onsem, May 14 '18 at 13:58

score 1 · Accepted Answer · answered May 14 '18 at 13:59

1

You shouldn't need to use conditional aggregation, you just need the sum

 queryset = queryset.annotate(
    sum_ = Sum('model_itemtransaction__item_sold')
 )

answered May 14 '18 at 13:59

Iain Shelvington

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Please consider marking my answer as the correct one – Iain Shelvington May 16 '18 at 04:27
Done. Sorry for the delay. Thought I did it yesterday. – Fxs7576 May 16 '18 at 04:28

Getting the aggregate sum of a field from the other model in Listview

models.py

views.py

1 Answers1