Merging timeseries in postgres

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От Tim Smith
Тема Merging timeseries in postgres
Дата
Msg-id CA+HuS5E8bSoRxQYeuHyE2uacY87m8Yg1RaDx6ZjLnKiGLMZpQg@mail.gmail.com
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Ответы Re: Merging timeseries in postgres  ("David G. Johnston" <david.g.johnston@gmail.com>)
Re: Merging timeseries in postgres  (Nick Babadzhanian <nb@cobra.ru>)
Re: Merging timeseries in postgres  (Nick Babadzhanian <nb@cobra.ru>)
Список pgsql-general
Hi,

I've got a bit of query-writers block ! I've tried various join styles
but can't get it to do what I want to achieve.

Assume I have a bunch of time-series tables :

create table test(dx date,n numeric);
create table test1(dx1 date,nx1 numeric);
insert into test values('2000-01-01','0.001');
insert into test1 values('2002-01-02','0.002');
insert into test1 values('2003-01-03','0.002');

What I want to do is create a view that merges these together with
time as the index, i.e the output would look like :


2000-01-01  0.001  (null)
2002-01-02  (null)   0.002
2003-01-03  (null)   0.003

I can't quite figure out how to keep the index independent and make a
clean join, typical outer join constructs end up with results like :

 dx | nx |    dx1     |  nx1
----+----+------------+-------
    |    | 2002-01-02 | 0.001
    |    | 2003-01-02 | 0.002
(2 rows)

     dx     |  nx   |    dx1     |  nx1
------------+-------+------------+-------
 2000-01-02 | 0.005 |            |
            |       | 2002-01-02 | 0.001
            |       | 2003-01-02 | 0.002


Which isn't very pretty and doesn't really achieve what I want.

As I said "sql-writers block !"   ;-(

Tim


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