In response to Dave Clarke <pigwin32@xxxxxxxxx>: > > I have a table that I'm trying to refactor and I'm by no means a SQL > expert (apologies if I'm posting to the wrong group). The table in > question has a column that allows NULLs. I want to move that column > into a separate table and set up a FK reference back to the original > table. My question is whether this is the correct way to refactor this > table. > > Original table (other columns elided) > > PurchaseOrder > --------------------- > POType > PONum > ServiceProviderNum > WorkOrderRef (NULLs allowed) > > PK: POType + PONum > Candidate Key: PONum + ServiceProviderNum > > Proposed structure > > PurchaseOrder > --------------------- > POType > PONum > ServiceProviderNum > > PK: PONum + ServiceProviderNum > > WorkOrder > --------------- > PONum > ServiceProviderNum > WorkOrderRef (NULLs not allowed) > > PK: PONum + ServiceProviderNum > FK: PurchaseOrder( PONum + ServiceProviderNum) > > Does that make sense? My intention is to be able to join PurchaseOrder > and WorkOrder to get the set of PurchaseOrder's that have been > assigned WorkOrderRef's. As I understand it, FK's are generally used > for 1 to many relationships where as this is expressing a 1 to 1 > relationship. > > I would be very grateful for any assistance with this. Thanks, Dave You can certainly do what you're describing and it will work well. I am curious as to why you'd want to, though. What problem are you trying to solve by doing this? I don't see it being worth the extra complexity and size you've added to the schema. -- Bill Moran http://www.potentialtech.com http://people.collaborativefusion.com/~wmoran/ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
