Referential Integrity does allow a NULL foreign key constraint. I know SQL Server supports this. If you enter a value, it must exist in the referenced table but until you know the value, a NULL is acceptable.

I'm not sure how VFP supports this. However, your design is logical and if there is a limitation, it may be with VFP.


>>Steve Sawyer has new RI code in his book (Effective Techniques for Application Development with Visual FoxPro) that will allow you to change to a different value, but I don't know if it will support NULL.
>
>Thanks Craig. I will take a look at it tonight.
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>If Steve is doing something like this, it must be legit.