Re: NULLS and string concatenation

On Fri, 19 Nov 2004 17:48:34 +0000, Richard Huxton <dev(at)archonet(dot)com> wrote:
> Don Drake wrote:
> > select 'some text, should be null:'|| NULL
> >
> > This returns NULL and no other text. Why is that? I wasn't expecting
> > the "some text.." to disappear altogether.
> >
> > Is this a bug?
>
> No. Null is "unknown" if you append unknown (null) to a piece of text,
> the result is unknown (null) too.
>
> If you're using NULL to mean something other than unknown, you probably
> want to re-examine your reasons why.
>

I'm using NULL to mean no value. Logically, NULL is unknown, I agree.

I'm trying to dynamically create an INSERT statement in a function
that sometimes receives NULL values.

This is still strange to me. In Oracle, the same query would not
replace the *entire* string with a NULL, it treats the NULL as a no
value.

I can't find in the documentation where string concatenation of any
string and NULL is NULL.

-Don