From: | Jonathan Moules <jonathan-lists(at)lightpear(dot)com> |
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To: | David G(dot) Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> |
Cc: | "pgsql-sql(at)postgresql(dot)org" <pgsql-sql(at)postgresql(dot)org> |
Subject: | Re: Always getting back a row, even with no results |
Date: | 2017-08-11 15:36:21 |
Message-ID: | 15dd1ef824a.11e71b280106536.5163340769196231808@lightpear.com |
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Lists: | pgsql-sql |
Hi David,
I'm afraid I don't really understand this response (I've not done much with arrays), but it doesn't seem to work for my purpose.
No NULL is returned if there is no result (i.e. cat = 50); instead, there's simply no rows.
What aspect of Arrays is this trying to take advantage of?
Cheers,
Jonathan
---- On Fri, 11 Aug 2017 16:18:04 +0100 David G. Johnston<david(dot)g(dot)johnston(at)gmail(dot)com> wrote ----
On Fri, Aug 11, 2017 at 6:57 AM, Jonathan Moules <jonathan-lists(at)lightpear(dot)com> wrote:
This will of course return the two rows with that category. But I also want to be able to run the query with a non-existent cat and get a result of "null" for the id.
untested
SELECT unnest( ARRAY( (
select id from my_table where cat = 50 ) ) );
tested, self-contained, example:
SELECT unnest(ARRAY((SELECT col FROM ( VALUES (1), (2) ) vals (col) WHERE true)))
David J.
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