Date: Sat, 21 May 2011 08:58:49 +0200
From: Andreas Kretschmer <akretschmer@spamfence.net>
To: pgsql-sql@postgresql.org
Subject: Re: unnest in SELECT
Message-ID: <20110521065849.GA5587@tux>
References: <4DD6C4CD.40406@optonline.net>
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Karl Koster <klkoster@optonline.net> wrote:

> I have a couple of questions regarding unnest.
>
> 1) If I issue a select statement "select unnest(vector1) as v from  
> some_table", I cannot seem to use the column alias v in a WHERE or  
> HAVING clause. I can use it in an ORDER BY or GROUP by clause. Is this  
> the way it is supposed to work?

Yes. It's the same as:

test=# select 1 as a where a = 2;
ERROR:  column "a" does not exist
LINE 1: select 1 as a where a = 2;

in other words: the column a is unknown for the where-condition at this
time.

>
> 2) If I issue a select statement "select unnest(vector1) as v1,  
> unnest(vector2) as v2 from some_table" and vector1 has a length of 3 and  
> vector2 has a length of 4, the result set will have 12 rows with the  
> data of vector1 repeating 4 times and vector2 repeating 3 times.

Yeah, it's a cross-join.


Andreas
-- 
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