Hi Thanks for the reply. I’ve accidentally pushed the send button before finish the message. 🤦🏻♂️
Regards, Wladimir > Em 1 de jul. de 2021, à(s) 10:25, Hannes Ljungberg > <hannes.ljungb...@gmail.com> escreveu: > > Hi! > > Support for using expressions on UniqueConstraints will be available in > Django 4.0: > https://docs.djangoproject.com/en/dev/releases/4.0/#functional-unique-constraints > > <https://docs.djangoproject.com/en/dev/releases/4.0/#functional-unique-constraints> > > torsdag 1 juli 2021 kl. 15:23:21 UTC+2 skrev wladimir....@gmail.com > <http://gmail.com/>: > Hello, > First of all, you've being doing a great work here. Django is an amazing > framework! > > I have been woking in a new project and I need to do a multiple columns > unique validation in which some of them is nullable. So I've use a > UniqueConstraint like: > > class Item(Model): > name = models.CharField(max_length=200, null=False) > unit = models.CharField(max_length=20, null=True) > owner = models.CharField(max_length=200, null=True) > class Meta: > constraints = [ > models.UniqueConstraint( > name='%(app_label)s_%(class)s_name_unit_owner_uniq', > fields=('name', 'unit', 'owner') > ), > ] > > Unfortunately I wasn't achieving what I wanted. In that simple example a user > could create duplicated records for unit = None. Also, It is possible to > create duplicated records where .This behavior conforms the SQL standards, of > course. > In this article > <https://wladimirguerra.medium.com/only-one-null-in-unique-columns-234672fefc08> > I explain how I have done to get the wanted behavior and the reasons that it > might be cumbersome in some cases. In the same article I show an SQL > expression that is clean and should result in a way more DRY code in model > declaration. The SQL expression is: > > CREATE UNIQUE INDEX core_item_name_unit_owner_uniq > ON public.core_item (name, COALESCE(owner,"-"), COALESCE(unit,"-")); > > > -- > You received this message because you are subscribed to a topic in the Google > Groups "Django developers (Contributions to Django itself)" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/django-developers/zqszCYWzxDI/unsubscribe > <https://groups.google.com/d/topic/django-developers/zqszCYWzxDI/unsubscribe>. > To unsubscribe from this group and all its topics, send an email to > django-developers+unsubscr...@googlegroups.com > <mailto:django-developers+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-developers/388b0350-bfd7-4e5f-a3c9-f963f2ab2eb6n%40googlegroups.com > > <https://groups.google.com/d/msgid/django-developers/388b0350-bfd7-4e5f-a3c9-f963f2ab2eb6n%40googlegroups.com?utm_medium=email&utm_source=footer>. -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/C65DB4B7-FE70-44CE-9ACA-064FDC53AC16%40gmail.com.
