Re: How to fetch values at regular hours?

Yes timestamp and count - is not good names for columns...

I tried something like;

select name,date_trunc('hour',timestamp),timestamp,count from
counter_log_view where name='CNT-3' and timestamp < '2010-05-23 20:00:00'
order by timestamp limit 10;
name | date_trunc | timestamp | count
-------+---------------------+----------------------------+-------
CNT-3 | 2010-05-23 15:00:00 | 2010-05-23 15:43:17.411386 | 23
CNT-3 | 2010-05-23 15:00:00 | 2010-05-23 15:53:17.45934 | 24
CNT-3 | 2010-05-23 16:00:00 | 2010-05-23 16:03:17.489321 | 24
CNT-3 | 2010-05-23 16:00:00 | 2010-05-23 16:13:17.586089 | 24
CNT-3 | 2010-05-23 16:00:00 | 2010-05-23 16:23:17.69116 | 25
CNT-3 | 2010-05-23 16:00:00 | 2010-05-23 16:33:17.795955 | 28
CNT-3 | 2010-05-23 16:00:00 | 2010-05-23 16:43:17.89265 | 28
CNT-3 | 2010-05-23 16:00:00 | 2010-05-23 16:53:17.989268 | 30
CNT-3 | 2010-05-23 17:00:00 | 2010-05-23 17:03:18.1447 | 33
CNT-3 | 2010-05-23 17:00:00 | 2010-05-23 17:13:18.199568 | 35
(10 rader)

Seems promising... But then I would like to select only the last from
date_trunc...

Hm...

GH

2010/5/25 Tim Landscheidt <tim(at)tim-landscheidt(dot)de>

> Goran Hasse <gorhas(at)gmail(dot)com> wrote:
>
> > [...]
> > I would like to do;
>
> > freescada=> select * from counter_log_view where name='CNT-3' and
> timestamp
> > < '2010-05-23 18:00:00' order by timestamp desc limit 1;
> > name | timestamp | count
> > -------+---------------------------+-------
> > CNT-3 | 2010-05-23 17:53:18.58674 | 43
> > (1 rad)
>
> > freescada=> select * from counter_log_view where name='CNT-3' and
> timestamp
> > < '2010-05-23 19:00:00' order by timestamp desc limit 1;
> > name | timestamp | count
> > -------+----------------------------+-------
> > CNT-3 | 2010-05-23 18:53:19.151988 | 50
> > (1 rad)
>
> > freescada=> select * from counter_log_view where name='CNT-3' and
> timestamp
> > < '2010-05-23 20:00:00' order by timestamp desc limit 1;
> > name | timestamp | count
> > -------+----------------------------+-------
> > CNT-3 | 2010-05-23 19:53:19.683514 | 51
> > (1 rad)
>
> > In one query. Is this possible in *any* way?
>
> Sure:
>
> | SELECT DISTINCT ON (DATE_TRUNC('hour', timestamp)) name, timestamp, count
> | FROM counter_log_view
> | ORDER BY DATE_TRUNC('hour', timestamp), timestamp DESC;
>
> Tim
>
> P. S.: Naming columns "timestamp" and "count" will lead to
> trouble :-).
>
>
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--
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