On Mon, 2011-05-02 at 20:06 -0600, Rob Sargent wrote:
> Jeff Davis wrote:
> > In particular, I think you are falsely assuming that a natural key must
> > be generated from an outside source (or some source outside of your
> > control), and is therefore not reliably unique.
> >
> > You can generate your own keys...
...
> My wife works (at the sql level) with shall we say "records about
> people". Real records, real people. Somewhere around 2 million unique
> individuals, several million source records. They don't all have ssn,
> they don't all have a drivers license. They don't all have an address,
> many have several addresses (especially over time) and separate people
> have at one time or another lived at the same address. You would be
> surprise how many "bob smith"s where born on the same day. But then
> they weren't all born in a hospital etc etc etc. A person may present
> on any of a birth record, a death record, a hospital record, a drivers
> license, a medical registry, a marriage record and so on. There simply
> is no natural key for a human. We won't even worry about the
> non-uniqueness of ssn. And please don't get her started on twins. :)
>
>
> I can only imagine that other equally complex entities are just as
> slippery when it comes time to pinpoint the natural key.
I think you missed my point. You don't have to rely on natural keys that
come from somewhere else; you can make up your own, truly unique
identifier.
Regards,
Jeff Davis