You would either have to duplicate the Title foreign key in the Copy model or write a custom check in the save method.
To enforce uniqueness over several columns you would use the "unique_together" field of the Meta class for your Copy model. (see: http://www.djangoproject.com/documentation/model-api/#unique-together) This creates the appropriate unique index for your table. However, this means you can only enforce uniqueness for fields within an individual model. Nathan On Jul 6, 11:30 am, "Todd O'Bryan" <[EMAIL PROTECTED]> wrote: > I'm writing an app to deal with checking out textbooks to students. The > models are > > Title: > the book > PurchaseGroup: > when purchased and how much they cost, foreign key to Title > Copy: > number, foreign key to PurchaseGroup > > I'd like to make it so that no two copies have the same number and > title, i.e. copies #1 and #2 of The Django Book are legal as is copy #1 > of The Mythical Man-Month, but having two copy #1's of the same book > would be forbidden. > > Will the ORM do that, or do I have to just write a check in the Copy > class's save method? > > Thanks! > Todd --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
