Re: thinking about UPDATE
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Thu, 29 Jul 2004 18:29:51 GMT
Message-ID: <pan.2004.07.29.18.30.54.700962_at_REMOVETHIS.pandora.be>
>
> From a set of constraints.
> For example FD, MVD, JD, inclusion dependencies, and maybe interval
> constraints, cardinality constraints.
Date: Thu, 29 Jul 2004 18:29:51 GMT
Message-ID: <pan.2004.07.29.18.30.54.700962_at_REMOVETHIS.pandora.be>
On Thu, 29 Jul 2004 09:12:36 +0300, x wrote:
> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> news:pan.2004.07.28.16.12.50.907297_at_REMOVETHIS.pandora.be...
>> >> Which problem exactly? To derive the CKs in the projection given a set >> of CKs in the original relation? That algorithm I already gave in this >> thread. Or do you want to start from a set of FDs?
>
> From a set of constraints.
> For example FD, MVD, JD, inclusion dependencies, and maybe interval
> constraints, cardinality constraints.
It's always going to be exponential for the simple reason that that is the potential size of the output. Of the dependencies only the FDs are actually relevant, you can ignore the rest, and for those you can use the usual algorithm.
- Jan Hidders