I have a query akin to the following:
SELECT SUM(ISNULL(table.name)) FROM table
How does that SUM
translate into a QuerySet
in Django? i.e. What operation xyz
does it translate to, in something like MyModel.objects.xyz()
?
You simply using values() , aggregate() and function Avg() and F() .
When specifying the field to be aggregated in an aggregate function, Django will allow you to use the same double underscore notation that is used when referring to related fields in filters. Django will then handle any table joins that are required to retrieve and aggregate the related value.
In the Django QuerySet API, F() expressions are used to refer to model field values directly in the database.
Update: The following incorporates the ISNULL aspect of the original query:
from django.db.models import Sum ModelName.objects.filter(field_name__isnull=True).aggregate(Sum('field_name')) # returns {'field_name__sum': 1000} for example
You're looking for the Sum aggregation function, which works as follows:
ModelName.objects.aggregate(Sum('field_name'))
See: https://docs.djangoproject.com/en/dev/ref/models/querysets/#sum
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