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Posted by Gert-Jan Strik on 06/01/05 13:20
Maybe the addresses you are using are never shared, but (unless this is
a business rule), this is purely coincidental. An address is an entity.
And with a foreign key relation you can specify that a publisher or an
agency has an address. It is not even uncommon to have several such
relations between two entities. For example, a publisher could have a
billing address and a shipping address. That would mean two
relationships to (potentially) the same address.
Looking at the address as being "properties" of a publisher is not the
way a relational database works.
If it is a business rule that addresses "must not be shared" then that
is a different matter which is probably best solved by writing a
trigger.
Gert-Jan
martind-crap1@mailblocks.com wrote:
>
> These are all very good thoughts, thanks. What happens if I have
> multiple n-to-1 relationships to the same child (e.g.
> Publisher-Address, Agency-Address -- but Addresses are never shared
> among entities) and I want to make them bidirectional?
>
> Items to consider:
> - All primary keys are enterprise keys (unique across all associated
> databases and tables).
> - Only one application has write-access to my data model
> - I want a data model that is resilient to change ... if I introduce
> another entity with an Address, I don't want to have to add another
> foreign key column
>
> What are some potential downsides to giving up referential integrity?
>
> Thanks!
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