
> > Actually I am not sure whether the column = NULL syntax is even defined 
> > or allowed in SQL92 (e.g. Informix interprets the NULL as column name in 
> > this context and errs out).
> 
> I don't have the standard handy, but I do have Joe Celko's book, "Data
> & Databases: Concepts in Practice".  He says (in section 8.2, under
> the heading "Multivalued Logic"):
> 
>         A NULL cannot be compared to another NULL or to a value

I mean that I am not sure NULL is a valid constant in a where clause 
comparison.
Thus it could be, that NULL in "where column = NULL" is not defined 
to have a special meaning according to SQL92.

NULL is probably only defined in a special context, like:
	IS NULL
	IS NOT NULL

Andreas

Thu, 7 Jun 2001 13:38:46 +0200 
Zeugswetter Andreas SB  <ZeugswetterA@wien.spardat.at>
AW: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. S
	tand ards
Zeugswetter Andreas SB <ZeugswetterA@wien.spardat.at> writes:

> Thus it could be, that NULL in "where column = NULL" is not defined 
> to have a special meaning according to SQL92.

The way I interpret Celko's interpretation of SQL92, that specific
construct has a meaning; it evaluates to UNKNOWN, thus not to TRUE,
and the WHERE clause becomes useless, as does any other combination of
a theta operator and the explicit constant 'NULL'.  This is almost,
but not quite, an argument for allowing "= NULL" for "IS NULL".  ;-)

Does anyone out there have the actual text of the standard?

-tih
-- 
The basic difference is this: hackers build things, crackers break them.

07 Jun 2001 14:46:50 +0200
Tom Ivar Helbekkmo <tih@kpnQwest.no>
Re: AW: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. S tand ards
On Thu, Jun 07, 2001 at 02:46:50PM +0200, Tom Ivar Helbekkmo wrote:
> Zeugswetter Andreas SB <ZeugswetterA@wien.spardat.at> writes:
> 
> > Thus it could be, that NULL in "where column = NULL" is not defined 
> > to have a special meaning according to SQL92.
> 
> The way I interpret Celko's interpretation of SQL92, that specific
> construct has a meaning; it evaluates to UNKNOWN, thus not to TRUE,
> and the WHERE clause becomes useless, as does any other combination of
> a theta operator and the explicit constant 'NULL'.  This is almost,
> but not quite, an argument for allowing "= NULL" for "IS NULL".  ;-)
> 
> Does anyone out there have the actual text of the standard?
> 
> -tih

I dont know the standard for that, but to add an experience in another
server (Interbase), '= null' has no meaning in Interbase, ie, doesnt
works as 'IS NULL'.

Sergio Bruder

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pub  1024D/0C7D9F49 2000-05-26 Sergio Devojno Bruder <bruder@conectiva.com.br>
     Key fingerprint = 983F DBDF FB53 FE55 87DF  71CA 6B01 5E44 0C7D 9F49
sub  1024g/138DF93D 2000-05-26

Thu, 7 Jun 2001 09:57:50 -0300
Sergio Bruder <bruder@conectiva.com.br>
Re: AW: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. S tand ards