| From: | "Daniel Schuchardt" <daniel_schuchardt(at)web(dot)de> |
|---|---|
| To: | <pgsql-general(at)postgresql(dot)org> |
| Cc: | <dev(at)archonet(dot)com> |
| Subject: | Re: <no subject> |
| Date: | 2003-10-01 10:32:21 |
| Message-ID: | 000001c38807$53c369d0$6500a8c0@DSVAIO |
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| Thread: | |
| Lists: | pgsql-general |
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(at)archonet(dot)com [mailto:dev(at)archonet(dot)com]
Gesendet: Mittwoch, 1. Oktober 2003 12:08
An: Daniel Schuchardt; pgsql-general(at)postgresql(dot)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
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