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Reply-To: <gnanam@zoniac.com>
From: "Gnanakumar" <gnanam@zoniac.com>
To: "'Dmitriy Igrishin'" <dmitigr@gmail.com>
Cc: <pgsql-sql@postgresql.org>
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Subject: Re: Is it possible to get DISTINCT rows from RETURNING clause?
Date: Mon, 21 Feb 2011 17:20:41 +0530
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Hi Dmitriy Igrishin,

Thanks.  That's a good idea too.

From: Dmitriy Igrishin [mailto:dmitigr@gmail.com] 
Sent: Saturday, February 19, 2011 3:31 PM
To: gnanam@zoniac.com
Cc: pgsql-sql@postgresql.org
Subject: Re: [SQL] Is it possible to get DISTINCT rows from RETURNING clause?

Hey Gnanakumar,

You can wrap you UPDATE query into SQL function returning TABLE, e.g:

CREATE OR REPLACE FUNCTION public.update_mytable()
 RETURNS TABLE(email text, column1 text, column2 text, column3 text)
 LANGUAGE sql
AS $function$
UPDATE MYTABLE SET ABOOLEANCOLUMN = true FROM MYTEMPTABLE WHERE EMAIL =
MYTEMPTABLE.EMAIL RETURNING EMAIL, COLUMN1, COLUMN2, COLUMN3;
$function$;

Next you can write, e.g:
SELECT DISTINCT * FROM
  (SELECT update_mytable()) AS foo(email, column1, column2, column3);

And so on.
2011/2/18 Gnanakumar <gnanam@zoniac.com>
Any ideas?

-----Original Message-----
From: Gnanakumar [mailto:gnanam@zoniac.com]
Sent: Thursday, February 17, 2011 12:36 PM
To: pgsql-sql@postgresql.org
Subject: Is it possible to get DISTINCT rows from RETURNING clause?

Hi,

Is it possible to get DISTINCT rows from an UPDATE statement using RETURNING
clause?

"MYTABLE" columns are:
       APRIMARYKEYCOLUMN
       ABOOLEANCOLUMN
       EMAIL
       COLUMN1
       COLUMN2
       COLUMN3

UPDATE using RETURNING clause query:
UPDATE MYTABLE SET ABOOLEANCOLUMN = true FROM MYTEMPTABLE WHERE EMAIL =
MYTEMPTABLE.EMAIL RETURNING EMAIL, COLUMN1, COLUMN2, COLUMN3;

Here in this case, I expect to return distinct rows from these columns:
EMAIL, COLUMN1, COLUMN2, COLUMN3.

I even tried out some ways of getting distinct rows, but it doesn't work.
Though I can still solve this at application layer, I'm trying to find
whether this could be controlled at query-level.  Any different
ideas/suggestions are appreciated.

Regards,
Gnanam


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-- 
// Dmitriy.