From: | Tim Smith <randomdev4+postgres(at)gmail(dot)com> |
---|---|
To: | pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Retrieving value of column X days later |
Date: | 2016-08-07 19:23:07 |
Message-ID: | CA+HuS5EPxEr1jrXnsE2Oe8cBEN-MTpGMe8jM8s=ghaYNZy8u2A@mail.gmail.com |
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Lists: | pgsql-general |
Hi,
Let's say I've got a table :
create table test (
when date,
foo numeric,
bar numeric,
alice numeric,
bob numeric);
insert into test values ('2016-01-01',1,2,3,4);
insert into test values ('2016-01-02',5,6,7,8);
insert into test values ('2016-01-03',9,10,11,12);
insert into test values ('2016-01-04',13,14,15,16);
insert into test values ('2016-01-05',17,18,19,20);
What I would like to do is the following :
(1) Given "select alice,bob from test where foo=1 and bar=2" I would
like to return the values of alice, bob *and* the value of foo four
days later (i.e. "17" in the above example).
(2) But there may be times where there are insufficient data points,
and so I would want to retrieve the last available value (e.g. "select
alice,bob from test where foo=9 and bar=10", there is 4 days hence,
therefore it would return the last available, i.e. "17" in this
example, even though that is only 2 days hence).
Any ideas welcome !
Thanks !
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