Re: NULLS and string concatenation

Someone on this list provided me with a rather elegant solution to this a few weeks ago:

CREATE OR REPLACE FUNCTION text_concat_nulls_with_an_embedded_space(text, text) RETURNS text AS 'SELECT CASE WHEN $1 IS
NULLTHEN $2 WHEN $2 IS NULL THEN $1 ELSE $1 || '' '' || $2 END' LANGUAGE sql; 

CREATE OPERATOR ||~ (PROCEDURE = text_concat_nulls_with_an_embedded_space, LEFTARG = text, RIGHTARG = text);

And I call it as:
SELECT (trim(s_directio) ||~ trim(s_house) ||~ trim(s_post_dir) ||~ trim(s_street) ||~ trim(s_suffix)) as street ...
(yaddayadda) 

Deals quite neatly with the NULLs in some of the columns.

HTH,

Greg Williamson
DBA
GlobeXplorer LLC

-----Original Message-----
From:    Michael Fuhr [mailto:mike@fuhr.org]
Sent:    Fri 11/19/2004 9:53 AM
To:    Don Drake; pgsql-sql@postgresql.org
Cc:
Subject:    Re: [SQL] NULLS and string concatenation
On Fri, Nov 19, 2004 at 11:45:43AM -0600, Bruno Wolff III wrote:
> On Fri, Nov 19, 2004 at 11:12:38 -0600, Don Drake <dondrake@gmail.com> wrote:
> >
> > I was able to work around the problem by using COALESCE (and casting
> > variables since it wants the same data types passed to it).
>
> This is what you should do.

If you don't mind using a non-standard feature, another possibility
would be to create an operator similar to || that COALESCEs NULLs
into empty strings.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/

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