How Can I Enforce Uniqueness on Django Model Fields When Some Are None?

Hi everyone,

I’m working on a Django model for storing addresses and need to enforce uniqueness across five fields: street, house_number, city, state, and zip_code. The complication is that one or more of these fields can be None, yet I want to avoid duplicate entries where all non-None fields match.

Here’s my model:

PYTHONCopied
class Address(models.Model):
    street = models.CharField(max_length=255, null=True, blank=True)
    house_number = models.CharField(max_length=50, null=True, blank=True)
    city = models.CharField(max_length=100, null=True, blank=True)
    state = models.CharField(max_length=2, null=True, blank=True)
    zip_code = models.CharField(max_length=10, null=True, blank=True)
    
    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=['street', 'house_number', 'city', 'state', 'zip_code'],
                name='unique_address_with_nulls',
            )
        ]

What I’m Trying to Achieve:

• Prevent duplicate entries where all non-None fields match.
• For example, these should be considered duplicates:
  1. street="123 Elm", house_number=None, city="Springfield", state="CA", zip_code="12345"
  2. street="123 Elm", house_number=None, city="Springfield", state="CA", zip_code="12345"

What is the best and most efficient way to achieve this? Thank you!