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 -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
