Re: BUG #6064: != NULL, <> NULL do not work [sec=UNCLASSIFIED]

Pilling, Michael wrote:
> Hi Kevin,
>
> Thanks for that. Point entirely taken. I think what I would add would
> be in the table 9-1 of operators, an extra column filled in only for
> =, <> and != saying Important: see difference from IS [NOT] NULL.
> Perhaps one reason I didn't pick up on this subtle issue is that IS
> NULL and IS NOT NULL are not listed in this table but they are
> comparison operators, just textual rather than symbolic ones in the
> grammar so they should be in the table. I recall specifically looking
> up what is the not equal operator in this language and only going
> forward from the table, not realising I had to read any further.
>
> I'd also add after "Do not write expression = NULL because NULL is not
> "equal to" NULL." Do not write expression != NULL or <> NULL because
> NULL is not "not equal to" NULL. because while implied, it's not
> obvious that because = doesn't work with NULL that != doesn't either.

I have written the attached patch to mention <> NULL also returns NULL.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +