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Re: Flatten table using timestamp and source - Mailing list pgsql-sql

From	Raj Mathur (राज माथुर)
Subject	Re: Flatten table using timestamp and source
Date	May 25, 2012 05:51:25
Msg-id	201205251120.46272.raju@linux-delhi.org Whole thread Raw
In response to	Re: Flatten table using timestamp and source (Elrich Marx <elrich.marx@rorotika.com>)
Responses	Re: Flatten table using timestamp and source
List	pgsql-sql
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On Thursday 24 May 2012, Elrich Marx wrote:
> If source changes, in this case from 1 to 2, then etime would be the
> last value of stime for source =1; So for source 1 it starts at
> stime 13:00 and continues till 13:02 (etime).
>
> This should result in 3 records, because source is 1, then 2, then 1
> again. I hope this explains ?

I think I understand.  Here's a partially working example -- it doesn't
compute the last interval.  Probably amenable to some severe
optimisation too, but then I don't claim to be an SQL expert :)

QUERY
-----
with first_last as (   select * from   (     selectsource,time,case  when    lag(source) over (order by time) != source
  or lag(source) over (order by time) is null  then 1 else 0end as is_first,case  when    lead(source) over (order by
time)!= source    or lead(source) over (order by time) is null  then 1 else 0end as is_last     fromp   ) foo   where
 is_first != 0 or is_last != 0 ) 
select t1.source, start_time, end_time
from (   select     source,     time as start_time   from     first_last   where     is_first = 1 ) t1 join (   select
  source,     time as end_time,     is_last   from     first_last   where     is_last = 1 ) t2 on (   t1.source =
t2.source  and t2.end_time > t1.start_time   and     t2.end_time <      (       select  timefrom  first_lastwhere
source!= t2.source  and time > t1.start_timeorder by  timelimit  1     ) ) 
;

DATA SET
--------source |        time
--------+---------------------     1 | 1970-01-01 05:30:01     1 | 1970-01-01 05:31:01     1 | 1970-01-01 05:32:01
6| 1970-01-01 05:33:01     6 | 1970-01-01 05:34:01     6 | 1970-01-01 05:35:01     6 | 1970-01-01 05:36:01     6 |
1970-01-0105:37:01     2 | 1970-01-01 05:38:01     2 | 1970-01-01 05:39:01     2 | 1970-01-01 05:40:01     2 |
1970-01-0105:41:01     6 | 1970-01-01 05:42:01     6 | 1970-01-01 05:43:01     6 | 1970-01-01 05:44:01     6 |
1970-01-0105:45:01     6 | 1970-01-01 05:46:01     4 | 1970-01-01 05:47:01     4 | 1970-01-01 05:48:01     4 |
1970-01-0105:49:01     4 | 1970-01-01 05:50:01     4 | 1970-01-01 05:51:01     0 | 1970-01-01 05:52:01     0 |
1970-01-0105:53:01     0 | 1970-01-01 05:54:01     0 | 1970-01-01 05:55:01     7 | 1970-01-01 05:56:01     7 |
1970-01-0105:57:01     7 | 1970-01-01 05:58:01     8 | 1970-01-01 05:59:01     8 | 1970-01-01 06:00:01     8 |
1970-01-0106:01:01     8 | 1970-01-01 06:02:01     8 | 1970-01-01 06:03:01     1 | 1970-01-01 06:04:01     1 |
1970-01-0106:05:01     1 | 1970-01-01 06:06:01     1 | 1970-01-01 06:07:01     1 | 1970-01-01 06:08:01     1 |
1970-01-0106:09:01     1 | 1970-01-01 06:10:01     8 | 1970-01-01 06:11:01     8 | 1970-01-01 06:12:01     8 |
1970-01-0106:13:01     6 | 1970-01-01 06:14:01     6 | 1970-01-01 06:15:01     6 | 1970-01-01 06:16:01     4 |
1970-01-0106:17:01     4 | 1970-01-01 06:18:01     9 | 1970-01-01 06:19:01     9 | 1970-01-01 06:20:01     9 |
1970-01-0106:21:01     9 | 1970-01-01 06:22:01     2 | 1970-01-01 06:23:01     2 | 1970-01-01 06:24:01     2 |
1970-01-0106:25:01     1 | 1970-01-01 06:26:01     1 | 1970-01-01 06:27:01     1 | 1970-01-01 06:28:01     1 |
1970-01-0106:29:01     4 | 1970-01-01 06:30:01     4 | 1970-01-01 06:31:01     4 | 1970-01-01 06:32:01     4 |
1970-01-0106:33:01     4 | 1970-01-01 06:34:01     0 | 1970-01-01 06:35:01     0 | 1970-01-01 06:36:01     0 |
1970-01-0106:37:01     9 | 1970-01-01 06:38:01     9 | 1970-01-01 06:39:01     9 | 1970-01-01 06:40:01     9 |
1970-01-0106:41:01     9 | 1970-01-01 06:42:01     1 | 1970-01-01 06:43:01     1 | 1970-01-01 06:44:01     1 |
1970-01-0106:45:01     8 | 1970-01-01 06:46:01     8 | 1970-01-01 06:47:01     8 | 1970-01-01 06:48:01     8 |
1970-01-0106:49:01     8 | 1970-01-01 06:50:01     0 | 1970-01-01 06:51:01     0 | 1970-01-01 06:52:01     0 |
1970-01-0106:53:01     0 | 1970-01-01 06:54:01     0 | 1970-01-01 06:55:01     0 | 1970-01-01 06:56:01     0 |
1970-01-0106:57:01     2 | 1970-01-01 06:58:01     2 | 1970-01-01 06:59:01     2 | 1970-01-01 07:00:01     2 |
1970-01-0107:01:01     2 | 1970-01-01 07:02:01     2 | 1970-01-01 07:03:01     2 | 1970-01-01 07:04:01     2 |
1970-01-0107:05:01     4 | 1970-01-01 07:06:01     4 | 1970-01-01 07:07:01     2 | 1970-01-01 07:08:01     2 |
1970-01-0107:09:01     2 | 1970-01-01 07:10:01     2 | 1970-01-01 07:11:01     2 | 1970-01-01 07:12:01     7 |
1970-01-0107:13:01     7 | 1970-01-01 07:14:01     9 | 1970-01-01 07:15:01     9 | 1970-01-01 07:16:01     9 |
1970-01-0107:17:01     7 | 1970-01-01 07:18:01     7 | 1970-01-01 07:19:01     7 | 1970-01-01 07:20:01     7 |
1970-01-0107:21:01 

RESULT
------source |     start_time      |      end_time
--------+---------------------+---------------------     1 | 1970-01-01 05:30:01 | 1970-01-01 05:32:01     6 |
1970-01-0105:33:01 | 1970-01-01 05:37:01     2 | 1970-01-01 05:38:01 | 1970-01-01 05:41:01     6 | 1970-01-01 05:42:01
|1970-01-01 05:46:01     4 | 1970-01-01 05:47:01 | 1970-01-01 05:51:01     0 | 1970-01-01 05:52:01 | 1970-01-01
05:55:01    7 | 1970-01-01 05:56:01 | 1970-01-01 05:58:01     8 | 1970-01-01 05:59:01 | 1970-01-01 06:03:01     1 |
1970-01-0106:04:01 | 1970-01-01 06:10:01     8 | 1970-01-01 06:11:01 | 1970-01-01 06:13:01     6 | 1970-01-01 06:14:01
|1970-01-01 06:16:01     4 | 1970-01-01 06:17:01 | 1970-01-01 06:18:01     9 | 1970-01-01 06:19:01 | 1970-01-01
06:22:01    2 | 1970-01-01 06:23:01 | 1970-01-01 06:25:01     1 | 1970-01-01 06:26:01 | 1970-01-01 06:29:01     4 |
1970-01-0106:30:01 | 1970-01-01 06:34:01     0 | 1970-01-01 06:35:01 | 1970-01-01 06:37:01     9 | 1970-01-01 06:38:01
|1970-01-01 06:42:01     1 | 1970-01-01 06:43:01 | 1970-01-01 06:45:01     8 | 1970-01-01 06:46:01 | 1970-01-01
06:50:01    0 | 1970-01-01 06:51:01 | 1970-01-01 06:57:01     2 | 1970-01-01 06:58:01 | 1970-01-01 07:05:01     4 |
1970-01-0107:06:01 | 1970-01-01 07:07:01     2 | 1970-01-01 07:08:01 | 1970-01-01 07:12:01     7 | 1970-01-01 07:13:01
|1970-01-01 07:14:01     9 | 1970-01-01 07:15:01 | 1970-01-01 07:17:01 

Regards,

-- Raj

> -----Original Message-----
> From: pgsql-sql-owner@postgresql.org
> [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Raj Mathur (???
> ?????)
> Sent: 24 May 2012 01:59 PM
> To: pgsql-sql@postgresql.org
> Subject: Re: [SQL] Flatten table using timestamp and source
>
> On Thursday 24 May 2012, Elrich Marx wrote:
> > I am quite new to Postgres, so please bear with me.
> >
> > I  have a table with data in the following format:
> >
> > Table name : Time_Source_Table
> >
> > Source , Stime
> > 1, "2012-05-24 13:00:00"
> > 1, "2012-05-24 13:01:00"
> > 1, "2012-05-24 13:02:00"
> > 2, "2012-05-24 13:03:00"
> > 2, "2012-05-24 13:04:00"
> > 1, "2012-05-24 13:05:00"
> > 1, "2012-05-24 13:06:00"
> >
> > I’m trying to get to a result  that flattens the results based on
> > source, to look like this:
> >
> > Source, Stime, Etime
> > 1, "2012-05-24 13:00:00","2012-05-24 13:02:00"
> > 2, "2012-05-24 13:03:00","2012-05-24 13:04:00"
> > 1, "2012-05-24 13:05:00","2012-05-24 13:06:00"
> >
> > Where  Etime is the last Stime for the same source.
>
> How do you figure out that the Etime for (1, 13:00:00) is (1,
> 13:02:00) and not (1, 13:01:00)?

--
Raj Mathur                          || raju@kandalaya.org   || GPG:
http://otheronepercent.blogspot.com || http://kandalaya.org || CC68
It is the mind that moves           || http://schizoid.in   || D17F
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Re: Flatten table using timestamp and source - Mailing list pgsql-sql

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