Re: DB design and foreign keys

[cut]

>
> It means what it says. You have defined table orders with a primary
> key of (id,order_code). This means that the combination of
> (id,order_code) must be unique.

yes, that was my thought, and in that context, i thought it could be
correct in order to have uniqueness for creating foreign keys

> So - these could all exist at the same time:
> (1,1), (1,2), (2,1), (2,2)
> You could not then add another (1,2) combination.

yes, again, i thought that was the uniqueness i needed...

>
> Since id and order_code are both just automatically-generated numbers
> in the orders table it doesn't add anything to make both of them part
> of a primary-key. I would delete the id column altogether and just
> have the order_code as the primary-key (since "order_code" carries
> more meaning to a human than "id"). This means your order_items table
> can then safely reference the order_code it wants to.

> HTH

sure it did, thanks for your response, best regards,
Gianluca Riccardi