Re: Retrieving value of column X days later

2016-08-07 22:23 GMT+03:00 Tim Smith <randomdev4+postgres(at)gmail(dot)com>:

> 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);
>

I had to rename column "when" into "when_d", as I do not like quoting
identifiers.

Try this query with window functions:

SELECT *,lead(foo,4) OVER (ORDER BY when_d),
last_value(foo) OVER (ORDER BY when_d RANGE BETWEEN UNBOUNDED
PRECEDING AND UNBOUNDED FOLLOWING)
FROM test;

This will give you the ability to lookup needed values.
You'll have to use subquery though, as window functions are evaluated after
the `WHERE` clause.

--
Victor Y. Yegorov