unique primary key shared between multiple tables.

In one of my database design textbooks, I ran across the following line:

PropertyForRent(propertyNo, ownerNo)

Foreign Key ownerNo references PrivateOwner(ownerNo) and BusinessOwner(ownerNo)

This implies that I can make PrivateOwner.ownerNo and BusinessOwner.ownerNo unique not just for thier respective tables, I can make ownerNo unique across both tables. In other words, no PrivateOwner.ownerNo may have the the same value as any BusinessOwner.ownerNo.

This would be extremely usefull, but I can't find any way to actually implement a shared primary key between tables. How do I do this?

Thanks,

Ben Received on Thu Mar 13 2003 - 23:31:16 CST