Re: [Firebird-docs] New doc: Firebird Null Guide

[Paul V. <pa...@vi...>]

Hi Fabricio,

> * Section "Testing if something is NULL"

> To my knowledge, is not a thing that is particular to FB the
> illegality of the expression "(A = NULL)".

Not particular to Fb alone; but e.g. MSSQL and Sybase (and maybe
others?) allow comparisons of the form "A = NULL". MSSQL even returns
True if A is indeed NULL. At least with the default setting of
ANSI_NULLS = OFF.

> AFAIK, this is part of SQL92 standard - the only operators that can
> tell the nullity / non-nullity of a given expression are the IS NULL
> / IS NOT NULL pair.

That's right, but some DBMSes are more relaxed (= less standard-
compliant) than Firebird here.

BTW, Firebird 2 will also legalise "A = NULL" comparisons, but they
will always return NULL.


Greetings,
Paul Vinkenoog