Обсуждение: 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:APRIMARYKEYCOLUMNABOOLEANCOLUMNEMAILCOLUMN1COLUMN2COLUMN3

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

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:APRIMARYKEYCOLUMNABOOLEANCOLUMNEMAILCOLUMN1COLUMN2COLUMN3

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

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)LANGUAGEsql
 
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.