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Re: returning more than one value from a function

From: Jasen Betts <jasen(at)xnet(dot)co(dot)nz>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: returning more than one value from a function
Date: 2010-05-01 03:46:30
Message-ID: hrg86m$186$1@reversiblemaps.ath.cx (view raw or flat)
Thread:
Lists: pgsql-novice
On 2010-04-30, Lonni J Friedman <netllama(at)gmail(dot)com> wrote:
> Greetings,
> I'm attempting to create a PL/PGSQL function with an IF/THEN
> conditional.  Basically, all I really need is the ability to run a
> long/complex SQL query based on the value of the newest row of one
> column in a specific table (if its equal to 1 then run the SQL, if
> anything else don't run it).  In pseudo code, something like:
>
> CREATE OR REPLACE FUNCTION foo0 RETURN text AS $$
> IF (SELECT current_status from table0 WHERE id in (SELECT max(id) FROM
> table0))='1' THEN
>      <LONG SQL QUERY>
> END IF;
> LANGUAGE 'plpgsql' ;
>
>

> This seems like a fairly simple requirement, yet I can't find any way
> to do this without creating a function. 

> The problem is that the
> long/complex SQL query needs to return multiple columns of output (not
> just a single value), and functions can only return a single
> value/column, so I'm a bit stuck on how to make this work.
>
> Is there an alternative solution that I'm missing?

 functions can return multple columns.

or you could try this:

 SELECT * FROM ( 
 
   <long sql query> 

 ) AS foo WHERE 
 
 ((SELECT current_status from table0 WHERE id in (SELECT max(id) FROM table0))='1')
 
 ;
 
the planner should be is smart enough to see that the where clause is
independant to the from clause and immutable and so evaluate it once.

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