On Sep 23, 5:43 am, AnthonyV <avequ...@gmail.com> wrote:
> Hello,
>
> I have a table like :
>
> date | value
> -------------------------------
> 2009-09-19 | 1
> 2009-09-20 | 2
> 2009-09-21 | 6
> 2009-09-22 | 9
> 2009-09-23 | 1
>
> I'd like a request which gives me the sum of each last n days.
> For example, if I want the sum of each 3 days, I want this result:
>
> date | sum_value
> -------------------------------
> 2009-09-19 | 1 (sum from 2009-09-17 to 2009-09-19)
> 2009-09-20 | 3 (sum from 2009-09-18 to 2009-09-20)
> 2009-09-21 | 9 (sum from 2009-09-19 to 2009-09-21)
> 2009-09-22 | 17 (sum from 2009-09-20 to 2009-09-22)
> 2009-09-23 | 16 (sum from 2009-09-21 to 2009-09-23)
>
> I try to make a subquery which is apply on each row of a query, but it
> does work.
>
> Has anybody an idea?
>
> Thanks in advance!
>
> Anthony
How about the following?
BEGIN ;
CREATE TABLE z ( the_date date not null,value integer not null
) ;
INSERT INTO z VALUES('2009-09-19',1) ;
INSERT INTO z VALUES('2009-09-20',2) ;
INSERT INTO z VALUES('2009-09-21',6) ;
INSERT INTO z VALUES('2009-09-22',9) ;
INSERT INTO z VALUES('2009-09-23',1) ;
SELECT z.the_date, SUM(z2.value) FROM z LEFT JOIN z z2 ON z2.the_date IN ( z.the_date
,z.the_date-'1 day'::interval ,z.the_date-'2 day'::interval )GROUP BY 1ORDER BY 1
;
ROLLBACK ;
output:
the_date | sum
------------+-----2009-09-19 | 12009-09-20 | 32009-09-21 | 92009-09-22 | 172009-09-23 | 16
(5 rows)
