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I have a model basically like this:
class Unit(models.Model):
name = models.CharField(max_length=64)
class UnitPrice(models.Model):
unit = models.ForeignKey(Unit, related_name="prices")
agency_fee = models.DecimalField(default=0.0, max_digits=7, decimal_places=2)
owner_fee = models.DecimalField(default=0.0, max_digits=7, decimal_places=2)
def amount(self):
return self.owner_fee + self.agency_fee
Is there a way to filter for amount (i.e. the sum of agency_fee and owner_fee) from Unit.objects?
513
I always assumed that chaining multiple filter() calls in Django was always the same as collecting them in a single call. The first queryset with the chained filter() calls joins the Inventory model twice effectively creating an OR between the two conditions whereas the second queryset ANDs the two conditions together.
The filter() method is used to filter you search, and allows you to return only the rows that matches the search term.
Returns a new QuerySet containing objects that match the given lookup parameters. Basically use get() when you want to get a single unique object, and filter() when you want to get all objects that match your lookup parameters.
all() Returns a copy of the current QuerySet (or QuerySet subclass). This can be useful in situations where you might want to pass in either a model manager or a QuerySet and do further filtering on the result. After calling all() on either object, you'll definitely have a QuerySet to work with.
Or simply transform a + b > c to a > c - b in order to use models.F expression:
UnitPrice.objects.filter(agency_fee__gt=10-models.F('owner_fee'))
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