In response to Richard Broersma : > On Thu, Dec 3, 2009 at 9:26 PM, Tom <tom@xxxxxxxxxxxxxxxxx> wrote: > > > I > > want run a query that skips every nth record and returns a managable > > dataset that still gives a correct overview of the data without > > slowing the programme down. Is there an easy way to do this that I > > have overlooked? I looked at: > > I've played with datalogging. It was very easy to find nth records > when using date_trunc() on a timestamp. The only minor problem with > data_trunc was that I couldn't create arbitrary granularity. For > example it is easy to date_trunc() on an year, month, week, day, hour > or a minute but I wanted 5, 10 and 15 minute increments. I bet there > could be a solution to this, but I never looked into it. How about: test=# select * from data limit 10; ts --------------------- 2009-12-01 00:00:00 2009-12-01 00:01:00 2009-12-01 00:02:00 2009-12-01 00:03:00 2009-12-01 00:04:00 2009-12-01 00:05:00 2009-12-01 00:06:00 2009-12-01 00:07:00 2009-12-01 00:08:00 2009-12-01 00:09:00 (10 rows) -- now with 5 miutes increments, using date_trunc and extract: test=# select * from data where extract(epoch from date_trunc('minute', ts))::int % (5*60) = 0 limit 10; ts --------------------- 2009-12-01 00:00:00 2009-12-01 00:05:00 2009-12-01 00:10:00 2009-12-01 00:15:00 2009-12-01 00:20:00 2009-12-01 00:25:00 2009-12-01 00:30:00 2009-12-01 00:35:00 2009-12-01 00:40:00 2009-12-01 00:45:00 (10 rows) Regards, Andreas -- Andreas Kretschmer Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header) GnuPG: 0x31720C99, 1006 CCB4 A326 1D42 6431 2EB0 389D 1DC2 3172 0C99 -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general