Re: FK - automatic value change when parent changes
Date: Sat, 27 Feb 2010 08:51:29 -0000
"joel garry" <joel-garry_at_home.com> wrote in message
> Problem with
> relational theory, it lacks time dynamism, it's not always just
> another attribute as you discover unelocuted requirements.
Not a problem - Chris Date cracked that a few years ago with a Hugh Darwen and another persons whose name I forget. Resulted in 6th Normal form, which collapsed to 5th Normal form in the absence of timedependency and time-dependent operators.
I think someone from Oracle had a presentation about their work in the same area a couple of years ago.
It allows "convenient" (though not necessary efficient) handling of queries like:
What would the data have looked like if I had queried it on 10th Feb allowing for the fact that there was an error on 9th Feb that wasn't corrected until 11th Feb - and I want to see the correct item, not the error.
-- Regards Jonathan Lewis http://jonathanlewis.wordpress.comReceived on Sat Feb 27 2010 - 02:51:29 CST