Обсуждение: Who knows this SELECT in PostgreSQL

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Who knows this SELECT in PostgreSQL

От
Michael Monnerie
Дата:
Dear gurus, I'm sure someone knows immediately how to translate this
mysql to postgresql:

SELECT GROUP_CONCAT(dbmail_messageblks.messageblk
ORDER BY dbmail_messageblks.is_header DESC SEPARATOR '')
FROM dbmail_messages
JOIN dbmail_messageblks ON
(dbmail_messages.physmessage_id=dbmail_messageblks.physmessage_id)
WHERE dbmail_messages.message_idnr='${MSG_UID}'
GROUP BY dbmail_messages.message_idnr"

It should simply return the whole message which can be truncated to
pieces into dbmail_messageblks and return it as a single entity. I found
this for mysql and would like to rewrite the shell script to postgresql,
but am stuck at this select.

mfg zmi
--
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Re: Who knows this SELECT in PostgreSQL

От
"Milen A. Radev"
Дата:
Michael Monnerie написа:
> Dear gurus, I'm sure someone knows immediately how to translate this
> mysql to postgresql:
>
> SELECT GROUP_CONCAT(dbmail_messageblks.messageblk
> ORDER BY dbmail_messageblks.is_header DESC SEPARATOR '')
> FROM dbmail_messages
> JOIN dbmail_messageblks ON
> (dbmail_messages.physmessage_id=dbmail_messageblks.physmessage_id)
> WHERE dbmail_messages.message_idnr='${MSG_UID}'
> GROUP BY dbmail_messages.message_idnr"
>
> It should simply return the whole message which can be truncated to
> pieces into dbmail_messageblks and return it as a single entity. I found
> this for mysql and would like to rewrite the shell script to postgresql,
> but am stuck at this select.
>
> mfg zmi


CREATE AGGREGATE public.array_agg(ANYELEMENT) (
    SFUNC = ARRAY_APPEND,
    STYPE = ANYARRAY,
    INITCOND = '{}'
);



SELECT
    ARRAY_TO_STRING(public.ARRAY_AGG(b.messageblk),'') AS the_message
FROM
    dbmail_messages AS m
JOIN
    dbmail_messageblks AS b
ON
    (m.physmessage_id = b.physmessage_id)
WHERE
    m.message_idnr = '${MSG_UID}'
GROUP BY
    m.message_idnr;






If you can wait for or want to test version 8.4 (which is in Beta
right now and would be released relatively soon) you can skip the
creation of the aggregate.


--
Milen A. Radev

Re: Who knows this SELECT in PostgreSQL

От
Michael Monnerie
Дата:
On Samstag 06 Juni 2009 Milen A. Radev wrote:
> CREATE AGGREGATE public.array_agg(ANYELEMENT) (
>     SFUNC = ARRAY_APPEND,
>     STYPE = ANYARRAY,
>     INITCOND = '{}'
> );
> SELECT
>     ARRAY_TO_STRING(public.ARRAY_AGG(b.messageblk),'') AS the_message

Wow, very cryptic. Would never have found that, thanks a lot!

> If you can wait for or want to test version 8.4 (which is in Beta
> right now and would be released relatively soon) you can skip the
> creation of the aggregate.

Need it now, but good to know 8.4 helps here :-)

mfg zmi
--
// Michael Monnerie, Ing.BSc    -----      http://it-management.at
// Tel: 0660 / 415 65 31                      .network.your.ideas.
// PGP Key:         "curl -s http://zmi.at/zmi.asc | gpg --import"
// Fingerprint: AC19 F9D5 36ED CD8A EF38  500E CE14 91F7 1C12 09B4
// Keyserver: wwwkeys.eu.pgp.net                  Key-ID: 1C1209B4