Date: Sat, 4 Jun 2011 21:36:23 -0400
From: lists-pgsql@useunix.net
To: pgsql-sql@postgresql.org
Subject: Re: selecting records X minutes apart
Message-ID: <20110605013623.GC16254@slacker.ja10629.home>
References: <20110603195253.GE1324@slacker.ja10629.home>
	<BANLkTikyu3jbxKucoyr_RH-2G6Ouq1H9oA@mail.gmail.com>
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Let's a take a look at just the input set for ID 0.

0       20:00
0       20:05
0       20:08
0       20:10

I want records, starting from the oldest record (20:00), that are at least 5
minutes apart.  So 20:00, 20:05, 20:10 but 20:08 - 20:05 is only 3 minutes so
it is to be ignored.

I was hoping to do this with a single SQL query that renders good runtime
performance but it may not possible. But I'm by no means proficient in SQL.

On Sat, Jun 04, 2011 at 05:51:18PM -0700, Kevin Crain wrote:
> Why is (0,20:10) listed in your expected results when there is a (0,20:08)?
> 
> 
> On Fri, Jun 3, 2011 at 12:52 PM,  <lists-pgsql@useunix.net> wrote:
> > I have a table that, at a minimum, has ID and timestamp columns.  Records
> > are inserted into with random IDs and timestamps.  Duplicate IDs are allowed.
> >
> > I want to select records grouped by ID, ordered by timestamp that are X minutes
> > apart. In this case X is 5.
> >
> > Note, the intervals are not X minute wall clock intervals, they are X minute
> > intervals from the last accepted record, per-id.
> >
> > For instance here is some sample input data:
> >
> > ID      TS (HH:MM)
> > -------------------
> > 0       20:00
> > 1       20:03
> > 1       20:04
> > 0       20:05
> > 1       20:05
> > 0       20:08
> > 1       20:09
> > 0       20:10
> >
> > I'd want the select to return:
> >
> > ID      TS (HH:MM)
> > -------------------
> > 0       20:00
> > 0       20:05
> > 0       20:10
> > 1       20:03
> > 1       20:09
> >
> >
> > Does my question make sense?
> >
> > Thanks in advance,
> > Wayne
> >
> > --
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> 
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