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* Is there a conditional string-concatenation ?
@ 2010-10-12 04:09 Andreas <maps.on@gmx.net>
0 siblings, 2 replies; 4+ messages in thread
From: Andreas @ 2010-10-12 04:09 UTC (permalink / raw)
To: pgsql-sql
Hi,
Is there a conditional string-concatenation ?
I'd like to have an elegant way to connect 2 strings with some 3rd
element between only if there really are 2 strings to connect.
e.g.
MyCat ( 'John', '_', 'Doe' ) --> 'John_Doe'
while
MyCat ( 'John', '_', '' ) --> 'John'
MyCat ( '', '_', 'Doe' ) --> 'Doe'
MyCat ( '', '_', '' ) --> NULL
It should treat NULL and '' equally as empty
and it should trim each of the 3 elements.
so
MyCat ( ' John ', '_', NULL ) --> 'John'
MyCat ( 'John', NULL, 'Doe' ) --> 'JohnDoe'
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Is there a conditional string-concatenation ?
@ 2010-10-12 04:18 Joshua Tolley <eggyknap@gmail.com>
parent: Andreas <maps.on@gmx.net>
1 sibling, 0 replies; 4+ messages in thread
From: Joshua Tolley @ 2010-10-12 04:18 UTC (permalink / raw)
To: Andreas <maps.on@gmx.net>; +Cc: pgsql-sql
On Tue, Oct 12, 2010 at 06:09:07AM +0200, Andreas wrote:
> Hi,
> Is there a conditional string-concatenation ?
Perhaps this:
CREATE OR REPLACE FUNCTION mycat(text, text, text) RETURNS TEXT LANGUAGE sql
IMMUTABLE AS $$
SELECT CASE
WHEN $1 IS NULL OR $1 = '' THEN trim($3)
WHEN $3 IS NULL OR $3 = '' THEN trim($1)
ELSE trim($1) || trim(coalesce($2, '')) || trim($3)
END;
--
Joshua Tolley / eggyknap
End Point Corporation
http://www.endpoint.com
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^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Is there a conditional string-concatenation ?
@ 2010-10-12 05:03 Osvaldo Kussama <osvaldo.kussama@gmail.com>
parent: Andreas <maps.on@gmx.net>
1 sibling, 1 reply; 4+ messages in thread
From: Osvaldo Kussama @ 2010-10-12 05:03 UTC (permalink / raw)
To: Andreas <maps.on@gmx.net>; +Cc: pgsql-sql
2010/10/12 Andreas <maps.on@gmx.net>:
> Hi,
> Is there a conditional string-concatenation ?
>
> I'd like to have an elegant way to connect 2 strings with some 3rd element
> between only if there really are 2 strings to connect.
>
> e.g.
> MyCat ( 'John', '_', 'Doe' ) --> 'John_Doe'
> while
> MyCat ( 'John', '_', '' ) --> 'John'
> MyCat ( '', '_', 'Doe' ) --> 'Doe'
> MyCat ( '', '_', '' ) --> NULL
>
> It should treat NULL and '' equally as empty
> and it should trim each of the 3 elements.
>
> so
> MyCat ( ' John ', '_', NULL ) --> 'John'
> MyCat ( 'John', NULL, 'Doe' ) --> 'JohnDoe'
>
Try:
bdteste=# SELECT nullif(ltrim(rtrim(coalesce(c1,'') || coalesce(c2,'')
|| coalesce(c3,''),' _'),' _'),'')
bdteste-# FROM (VALUES ('John', '_', 'Doe'),('John', '_', ''),('',
'_', 'Doe'),('', '_', ''),(' John ', '_', NULL),('John',
NULL, 'Doe')) AS foo(c1,c2,c3);
nullif
----------
John_Doe
John
Doe
John
JohnDoe
(6 rows)
Osvaldo
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Is there a conditional string-concatenation ?
@ 2010-10-12 09:01 Pavel Stehule <pavel.stehule@gmail.com>
parent: Osvaldo Kussama <osvaldo.kussama@gmail.com>
0 siblings, 0 replies; 4+ messages in thread
From: Pavel Stehule @ 2010-10-12 09:01 UTC (permalink / raw)
To: Osvaldo Kussama <osvaldo.kussama@gmail.com>; +Cc: Andreas <maps.on@gmx.net>; pgsql-sql
Hello
more simply
postgres=# CREATE OR REPLACE FUNCTION public.foo(a text, b text, c text)
RETURNS text
LANGUAGE sql
AS $function$
SELECT coalesce($1 || $2 || $3,
$1 || $2,
$2 || $3)
$function$
Regards
Pavel Stehule
2010/10/12 Osvaldo Kussama <osvaldo.kussama@gmail.com>:
> 2010/10/12 Andreas <maps.on@gmx.net>:
>> Hi,
>> Is there a conditional string-concatenation ?
>>
>> I'd like to have an elegant way to connect 2 strings with some 3rd element
>> between only if there really are 2 strings to connect.
>>
>> e.g.
>> MyCat ( 'John', '_', 'Doe' ) --> 'John_Doe'
>> while
>> MyCat ( 'John', '_', '' ) --> 'John'
>> MyCat ( '', '_', 'Doe' ) --> 'Doe'
>> MyCat ( '', '_', '' ) --> NULL
>>
>> It should treat NULL and '' equally as empty
>> and it should trim each of the 3 elements.
>>
>> so
>> MyCat ( ' John ', '_', NULL ) --> 'John'
>> MyCat ( 'John', NULL, 'Doe' ) --> 'JohnDoe'
>>
>
>
> Try:
> bdteste=# SELECT nullif(ltrim(rtrim(coalesce(c1,'') || coalesce(c2,'')
> || coalesce(c3,''),' _'),' _'),'')
> bdteste-# FROM (VALUES ('John', '_', 'Doe'),('John', '_', ''),('',
> '_', 'Doe'),('', '_', ''),(' John ', '_', NULL),('John',
> NULL, 'Doe')) AS foo(c1,c2,c3);
> nullif
> ----------
> John_Doe
> John
> Doe
>
> John
> JohnDoe
> (6 rows)
>
> Osvaldo
>
> --
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> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-sql
>
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-- links below jump to the message on this page --
2010-10-12 04:09 Is there a conditional string-concatenation ? Andreas <maps.on@gmx.net>
2010-10-12 04:18 ` Joshua Tolley <eggyknap@gmail.com>
2010-10-12 05:03 ` Osvaldo Kussama <osvaldo.kussama@gmail.com>
2010-10-12 09:01 ` Pavel Stehule <pavel.stehule@gmail.com>
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