> (external programming language)
> for ($i = 1; $i < 500; $i++) {
> // return me the "most recent" diag_value from a hardware_id $i
> // at the desired timestamp
> runquery("select diag_value from diagnose_logs where ts <= '2009-12-25
> 23:59:59' and hardware_id = $i order by ts desc limit 1");
> }
>
> can I turn this for-loop into a single query to run in postgres?
>
> Thanks,
> Pedro
>
Try:
SELECT diag_value FROM diagnose_logs a where id in
(
SELECT id FROM diagnose_logs b
WHERE a.hardware_id=b.hardware_id
and ts <= '2009-12-25 23:59:59'
and hardware_id between 1 and 500
ORDER BY ts LIMIT 1)
ORDER BY hardware_id;
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