Re:

Read the docs...

Hm looking towards the doks thats the right behavoir. Also from the
logical point thats the right behavoir. But I don't like it. The CAST
should return an empty string in that case (looking from the practical
standpoint).

Hm.


-----Ursprüngliche Nachricht-----
Von: dev@archonet.com [mailto:dev@archonet.com]
Gesendet: Mittwoch, 1. Oktober 2003 12:08
An: Daniel Schuchardt; pgsql-general@postgresql.org
Betreff: Re: [GENERAL] <no subject>


On Wednesday 01 October 2003 10:57, Daniel Schuchardt wrote:
> Hi @ all,
>
> I think thats a bug:
>
> SELECT '#' || '#'
>
> will work but
>
> SELECT '#' || CAST(NULL AS VARCHAR)

Nope - not a bug.

> will return only empty rows.
> My Query looks like this : SELECT field1 || field2 FROM ... If field2
> ISNULL then everything is null. CAST does not help.

Broadly speaking VALUE op NULL = NULL
You'll see similar issues with comparisons. You might find the article
below
useful:

http://techdocs.postgresql.org/guides/BriefGuideToNulls
--
  Richard Huxton
  Archonet Ltd