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 was able to work around the problem by using COALESCE (and casting
> variables since it wants the same data types passed to it).
That's the correct procedure (although ask yourself if you should have
nulls rather than just empty strings).
-- Richard Huxton Archonet Ltd