Date: Sun, 16 Oct 2011 10:27:06 +0200
From: Andreas Kretschmer <akretschmer@spamfence.net>
To: pgsql-sql@postgresql.org
Subject: Re: Group by on Date
Message-ID: <20111016082705.GB8614@tux>
References: <1318661510830-4904685.post@n5.nabble.com>
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maya.more <meena.mk@gmail.com> wrote:

> I have a table with Date and unit column. . I want to find sum of unit column
> considering 3 days each
> 
> User will specify start and enddate
> 
> Eg 
> 
> Date            Unit
> 10/1/2011     1
> 10/2/2011     2
> 10/3/2011      3
> 10/4/2011     4
> 10/5/2011     4
> 10/6/2011     1
> 10/7/2011     2 
> 10/8/2011     3
> 10/9/2011     1
> 10/10/2011    1
> 10/11/2011    1
> suppose if user selects date 10/1/2011  to 10/6/2011
> 
> then output should be
>  
> start date      enddate         unit
> 10/1/2011      10/3/2011     6
> 10/4/2011       10/6/2011    9
> 
> 
> pls let me know if anybody has any idea.

Maybe something like that:

test=*# select * from d;
     d      | i
------------+----
 2011-10-17 |  1
 2011-10-18 |  2
 2011-10-19 |  3
 2011-10-20 |  4
 2011-10-21 |  5
 2011-10-22 |  6
 2011-10-23 |  7
 2011-10-24 |  8
 2011-10-25 |  9
 2011-10-26 | 10
 2011-10-27 | 11
 2011-10-28 | 12
 2011-10-29 | 13
 2011-10-30 | 14
 2011-10-31 | 15
 2011-11-01 | 16
 2011-11-02 | 17
 2011-11-03 | 18
 2011-11-04 | 19
 2011-11-05 | 20
(20 rows)

Time: 0,276 ms
test=*# select '2011-01-01'::date + (extract(doy from d) / 3)::int *
'3day'::interval - '3day'::interval as "from", '2011-01-01'::date +
(extract(doy from d) / 3)::int * '3day'::interval as "to", sum(i) from d
group by 1,2 order by 1;
        from         |         to          | sum
---------------------+---------------------+-----
 2011-10-16 00:00:00 | 2011-10-19 00:00:00 |   6
 2011-10-19 00:00:00 | 2011-10-22 00:00:00 |  15
 2011-10-22 00:00:00 | 2011-10-25 00:00:00 |  24
 2011-10-25 00:00:00 | 2011-10-28 00:00:00 |  33
 2011-10-28 00:00:00 | 2011-10-31 00:00:00 |  42
 2011-10-31 00:00:00 | 2011-11-03 00:00:00 |  51
 2011-11-03 00:00:00 | 2011-11-06 00:00:00 |  39
(7 rows)

it fails for more than 1 year, but i hope, you can modify my sql for
your own.


Andreas
-- 
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