From: Jim <shakahshakah@gmail.com>
To: pgsql-sql@postgresql.org
Subject: Re: SQL Subqueries on each result row
Date: Wed, 23 Sep 2009 09:33:39 -0700 (PDT)
Message-ID: <d4bb176c-8e81-49bd-8160-e3b2a8eb3bd9@d23g2000vbm.googlegroups.com> (raw)
References: <b4fa00ca-986f-4a57-8690-e7d234ba6ebd@o21g2000vbl.googlegroups.com>
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 1
ORDER BY 1
;
ROLLBACK ;
output:
the_date | sum
------------+-----
2009-09-19 | 1
2009-09-20 | 3
2009-09-21 | 9
2009-09-22 | 17
2009-09-23 | 16
(5 rows)
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To: pgsql-sql@postgresql.org
Cc: shakahshakah@gmail.com
Subject: Re: SQL Subqueries on each result row
In-Reply-To: <d4bb176c-8e81-49bd-8160-e3b2a8eb3bd9@d23g2000vbm.googlegroups.com>
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