Re: So what's null then if it's not nothing?

From: <>
Date: 20 Nov 2005 13:58:43 -0800
Message-ID: <>

Hugo Kornelis wrote:

> On 17 Nov 2005 22:56:55 -0800, Marshall Spight wrote:
> (snip)
> >The question also arises as to what exactly SQL's null "is."
> >Is it unknown or empty? The answer, alas, is that it depends
> >on the context, a disastrously bad state of affairs.
> Hi Marshall,
> According to the ANSI specification, null has one and only one meaning:
> it's a marker to represent the absence of a value.
> So it's neither unknown, nor empty.

This just seems plain wrong to me. It surely is an empty set - or an empty thing. The thing surely exists. has this to say (among others):

Mathematics. Of or relating to a set having no members

Etymology: Anglo-French nul, literally, not any, from Latin nullus, from ne- not + ullus any

This is entirely consistent with Pick's null. An item, attribute, multivalue or subvalue can be either present and not null, present and null or absent. They are all valid and necessary. An empty set exists but has no members. A non-empty set can contain sets which are themselves empty. How unknown is represented is undefined - left up to the application designer.

Mike. Received on Sun Nov 20 2005 - 22:58:43 CET

Original text of this message