Re: [Sqlalchemy-users] Insane Difficult Modeling Question (Seems Easy)

[Koen Bok]

Maybe a little metaphor to make it more simple. Let's say I make houses. The roof of the house can either be concrete or wood. Concrete and wood come in many types. Design: House id name Wood id name treename Concrete id name hardness Now if I have a House object it should have a roof relation which either links to a Wood object or a Concrete object. It NEEDS to be linked to one of them. Like this: >>> house = session.query(House).get(1) >>> print house.roof <Concrete id=123 name=SuperBeautiful hardness=500> >>> house = session.query(House).get(2) >>> print house.roof < Wood id=321 name=Oak treename='Oak Tree'> On 16-jun-2006, at 5:24, Michael Bayer wrote: whats wrong with this ? order_types --------------- type_id name from_stock_id to_stock_id ? On Jun 15, 2006, at 6:44 PM, Koen Bok wrote: Within my organisation we have orders. Orders move products between three entities: Suppliers, Stocks and Customers. The type of an order gets defined by the origin and the destination it is moving products. This way we can have the following types of orders: From: To: -> Stock BUYORDER Stock -> Supplier RETOURBUYORDER Stock -> Stock INTERNORDER Stock -> Customer SELLORDER Customer ! -> Stock RETOURSELLORDER How can I design objects/mappers to do this: >>> order = session.query(Order).get(1) >>> print order.type <Type id=123 name='INTERNORDER' from=<Stock id=2> to=<Stock id=4>> >>> order = session.query(Order).get(2) >>> print order.type <Type id=456 name='SELLORDER' from=<Stock id=4> to=<Customer id=1928>> _______________________________________________ Sqlalchemy-users mailing list Sqlalchemy-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sqlalchemy-users

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