Re: NULLS and string concatenation

Slick ;o)

This goes in my tool kit...

On Friday 19 November 2004 03:03 pm, Gregory S. Williamson saith:
> 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 NULL THEN $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 ... (yadda yadda)
>
> Deals quite neatly with the NULLs in some of the columns.
>
> HTH,
>
> Greg Williamson
> DBA
> GlobeXplorer LLC
>
> -----Original Message-----
> From: Michael Fuhr [mailto:mike(at)fuhr(dot)org]
> Sent: Fri 11/19/2004 9:53 AM
> To: Don Drake; pgsql-sql(at)postgresql(dot)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(at)gmail(dot)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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