Re: array_cat without duplicity

On Wed, Mar 19, 2008 at 03:05:06PM +0100, Ondřej Fafejta wrote:
> Hi!
>
> Postgresql: version 8.1.11
>
> Is there a way to concatenate two arrays without duplicity?
>
> This select return duplicity:
>
> SELECT array_cat(ARRAY[1,2], ARRAY[2,3]);
> array_cat
> -----------
> {1,2,2,3}
>
> I need to get result without duplicity!
> {1,2,3}

Here's a function in SQL that does what you want.

CREATE OR REPLACE FUNCTION array_undup(ANYARRAY)
RETURNS ANYARRAY
LANGUAGE SQL
AS $$
SELECT ARRAY(
SELECT DISTINCT $1[i]
FROM generate_series(
array_lower($1,1),
array_upper($1,1)
) AS i
);
$$;

SELECT array_undup(array_cat(ARRAY[1,2], ARRAY[2,3]));
array_undup
-------------
{1,2,3}
(1 row)

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david(dot)fetter(at)gmail(dot)com

Remember to vote!
Consider donating to Postgres: http://www.postgresql.org/about/donate