Re: Group by on Date

maya.more <meena(dot)mk(at)gmail(dot)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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