When grilled further on (Mon, 19 Jan 2004 00:44:30 -0500),
Tom Lane <tgl@sss.pgh.pa.us> confessed:
> Robert Creager <Robert_Creager@LogicalChaos.org> writes:
> > ... one piece of data I need is the last value for each GROUP BY
> > period. Alas, I cannot figure out how to do this.
>
> SELECT DISTINCT ON (rather than GROUP BY) could get this done for you.
>
I had my whine all ready as to how I still couldn't figure it out, when I
figured it out:
...
SELECT p.period, etday
FROM (SELECT DISTINCT ON ( period ) date_trunc( 'hour', "when" ) AS period, etday FROM readings
ORDERBY period, "when" DESC) AS p
...
Thanks for the tip.
Cheers,
Rob
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