Re: Am I crazy or is this SQL not possible

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От Tom Lane
Тема Re: Am I crazy or is this SQL not possible
Дата
Msg-id 14505.1149189691@sss.pgh.pa.us
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Ответ на Am I crazy or is this SQL not possible  ("Collin Peters" <cadiolis@gmail.com>)
Ответы Re: Am I crazy or is this SQL not possible
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"Collin Peters" <cadiolis@gmail.com> writes:
> What I would like to do is simply get the last date_sent and it's
> status for every broadcast.  I can't do a GROUP BY because I can't put
> an aggregate on the status column.

You missed the key idea about how to use DISTINCT ON.

SELECT DISTINCT ON (email_broadcast_id) *
FROM email_broadcast_history
ORDER BY email_broadcast_id, date_sent DESC

You order by the DISTINCT ON fields, then one or more additional fields
to select the representative row you want within each DISTINCT ON group.
        regards, tom lane


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