🚀 go-pugleaf

On 28 Dec 2006 03:36:47 -0800, "Vladimir Stefanovic" <antivari@po.sbb.co.yu>
wrote:

>
>What the most recent standard say about linking FK to other entity?
>Has FK to be linked to PK of another entity, or it can by any
>other appropriate indexed field?

Hi Vladimir,       

    AFAIK, FK historically has to be linked to a PK because, the latter,
guarantees that it is unique, i.e. it characterizes one single row in the
recordset (aka a relation), so to make possible to create true master-detail
relationships. 
In this manner, is possible to "objectize" (i.e. to characterize each singe
element) of a relation (2NF), i.e. the recordset is a "set" and not a "bag".
Specifying the PF-FK realtionship directly in SQL using the appropriate
constraint, many RDBMS manage directly and automatically all the referential
integrity issues for you.

However, I suppose that you can try to link a FK to any other index (better if
with a unique constraint), comparing field values in a query joining (with a
join) the underlying tables. But I think that, if you want to recreate a sort
of referential integrity, you have to write some server side triggers.

Regards.

Giuliano