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

From: <michael_at_preece.net>
Date: 20 Nov 2005 19:58:44 -0800
Message-ID: <1132545524.199023.308850@f14g2000cwb.googlegroups.com>

Julian M wrote:

> michael_at_preece.net wrote:

> > Look - my final word on this.

Look - another final word...

> NULL in SQL can seem tricky, but it is simple enough if viewed in terms
> of what is intended by the ANSI SQL92/99 standards.
> See drafts:
> http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt
> http://www.ncb.ernet.in/education/modules/dbms/SQL99/
>

Here's your problem...

"A special value that is used to indicate the absence of any data value."

That's it right there. It doesn't make sense. The special value has to be present doesn't it? So something is present. What is it? Is it an indication that whatever it is is absent? Nope. If something is present it's present. If it's absent it's absent. This only makes sense if it is interpreted to mean that it, whatever it is, is empty, or void, of any value. Absence is the problem word. If I want something to be absent I'll delete it from the database. If I want to record that something does not have any data value I'll record a null. Pick doesn't need a special value to indicate this presence of a lack of any value - it just uses a lack of any value. I don't have a problem with SQL implementations using a special value if they're intrinsically unable to record the lack of any value as a lack of any value.

Also...

"A value of the Boolean data type is either true or false. The truth value of unknown is sometimes represented by the null value."

Dodgy or what?! It would be better to use a large cumbersome robot waving its arms about saying "does not compute" than to use null for this.

Mike.

PS. That's definitely it for me on this thread. Thanks and so long. Received on Sun Nov 20 2005 - 21:58:44 CST

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