Django Models
*************

- :doc:`dev-django-field`
- :doc:`dev-django-migrations`

``UniqueConstraint``
====================

Adapted from
`How to have unique=True email addresses while allowing for null=true`_

::

  from django.db import models
  from django.db.models import Q

  class Contact(TimedCreateModifyDeleteModel):
      # ...
      msgraph_user_uuid = models.UUIDField(null=True)

      class Meta:
          # ...
          # If we have a ``msgraph_user_uuid``, then it must be unique.
          constraints = [
              models.UniqueConstraint(
                  "msgraph_user_uuid",
                  name="constraint_unique_msgraph_user_uuid_no_null",
                  condition=Q(msgraph_user_uuid__isnull=False),
              )
          ]


.. _`How to have unique=True email addresses while allowing for null=true`: https://www.reddit.com/r/django/comments/14d7eqt/how_to_have_uniquetrue_email_addresses_while/