Re: Does Codd's view of a relational database differ from that ofDate& Darwin? [M.Gittens]

From: Alfredo Novoa <alfredo_novoa_at_hotmail.com>
Date: Tue, 07 Jun 2005 12:51:51 +0200
Message-ID: <32vaa1l02d4hu4p2h8asm0hbb9vopi82um@4ax.com>

On Mon, 06 Jun 2005 16:23:13 +0100, Paul <paul_at_test.com> wrote:

>OK so basically the problem is with aggregates?

The problem is basically with queries, but aggregate queries are probably the most problematic when we allow nulls.

>Why not say then that all aggregates that involve a NULL return NULL?

This is what SQL does. Sometimes we want to get a value but we get a null instead.

I have to mantain an application that breaks very often due to this problem.

>And if you want an actual result, you must specify an explicit behaviour
>by the use of COALESCE or WHERE clauses.

And this is very cumbersome and error prone.

>So could this actually be another problem with SQL's treatment of NULLs
>rather than with NULLs per se?

This problem is inherent to nulls.

Regards Received on Tue Jun 07 2005 - 05:51:51 CDT