Re: Geographic data sources, queries and questions

On May 29, 2007, at 15:28 , John D. Burger wrote:

> Even ISO country codes are not guaranteed to be stable

I'm not sure where the idea that primary keys must be stable comes
from. There's nothing necessarily wrong with updating a primary key.
All a primary key does is uniquely identify a row in a table. If that
id changes over time, that's fine, as long as the primary key columns
continue to uniquely identify each row in the table. SQL even
provides ON UPDATE CASCADE to make this convenient. There may be
performance arguments against updating a primary key (as the changes
need to propagate), but that depends on the needs of a particular
(benchmarked and tested) application environment.

Michael Glaesemann
grzm seespotcode net