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Date: Wed, 28 Mar 2007 07:27:29 -0700 (PDT)
From: Richard Broersma Jr <rabroersma@yahoo.com>
Subject: Re: union with count?
To: Gerardo Herzig <gherzig@fmed.uba.ar>, pgsql-sql@postgresql.org
In-Reply-To: <460A75ED.6070501@fmed.uba.ar>
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Message-ID: <437650.83949.qm@web31809.mail.mud.yahoo.com>


--- Gerardo Herzig <gherzig@fmed.uba.ar> wrote:

> Hi dudes, i have the following question
> i have 2 tables with the same format, and i want to know if is there a 
> possibility of using some sort of count(*) for achieving this result:
> select a from table1 where (condition) union select a from table2 where 
> (condition), count(a) group by a

I think you are showing count(a) in the wrong spot in your example.  But if I understand you
correctly the following should do what you want:

SELECT count(a)
FROM
(
    SELECT a
    FROM table1
    WHERE (your_condition = true)

UNION -- you can use UNION ALL if you 
      -- want rows that are duplicates from each table.

    SELECT a
    FROM table2
    WHERE (your_condition = true)
)
GROUP BY a;