Referential Integrity w/XOR

Hello,

I have a problem with referential integrity constraints that I'm not sure how to implement. I have three entities in which two are related to one common entity such as sales. The foreign key in the 'sales' table must reference a 'part' or 'service' but not both for a single row.

               | sales |     


               ---------

                  V V
                (_/_\_)
                 /   \
                /     \
               /       \
              /         \
        -----------   --------
        | service |   | part  |
        -----------   --------

There's no problem in defining a constraint for one relationship, but implemeting an XOR where a 'sales' item can be for either a 'service' or 'part' I can't find in the docs. Oracle tech support is clueless at the moment. I thought about using database triggers, but doing that would require preventing the insertion of a row in the 'sales' table which I can't find how to do.

Has anyone encountered this problem?

Thanks in advance for your help!

Mike Tuason
Cleveland Clinic Foundation
mtuason_at_bio.ri.ccf.org Received on Thu Jun 09 1994 - 20:08:17 CEST