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I'm working on a project in which I have an entity, we may call Users and another entity Address.

I want to define the entity User in a way that an user would have a collection of addresses (typically a One-To-Many relationship), but I also need an attribute of user, let it be main_address that would target a single value of the previous collection.

I would like to know if there is a conventional of doing this. The only solution I have now is to create another One-to-One relationship between Users . main_address and Address but this does not insure that the main_address will actually be part of the User . addresses collection.

I don't know if it could be important, because it's a rather theoretical question, but I'm using Doctrine 2.

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  • I could have written "good practice" or "better practice", but this wouldn't change my problem ... My question is NOT an opened question and I know I'm not the first to ask myself how to do this. I am quite sure there are some "good" solutions to my problem and I truely hope some of them will be posted here. I'll feel free to judge by myself which one seems the "best" to me. Commented Oct 26, 2014 at 20:25

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Add a field main_address_id in the User entity or table that holds the ID of the Address record that is the main one. Make that a one to one relationship, if you like.

The only solution I have now is to create another One-to-One relationship between Users.main_address and Address but this does not insure that the main_address will actually be part of the User.addresses collection.

Quite right. You need another mechanism that insures that. You can either validate that in your business logic, or use a stored procedure or trigger on the RDBMS during creation or editing of User that enforces this restriction.

Doctrine might have a "business rules" module that you can use. The point is that the additional restriction you are imposing on main_address_id doesn't have anything to do with your database schema, per se. It's a business rule, basically.

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  • You need another mechanism that insures that. Ok. I hope there could be a solution involving only the data models. My idea was there could be a way to make the main_address_id refers to an item of the collection, rather to an Address Commented Oct 26, 2014 at 20:35
  • I think finagling the model in that way would pollute it too much. The model is intended to describe the business's data domain, not necessarily to capture all of its rules. Commented Oct 26, 2014 at 20:38
  • I don't really share your point of view but I don't think it's a good idea to debate on this. Thank you for your help, i'm fixed now. Commented Oct 26, 2014 at 20:44

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