Re: R: One column to multiple columns based on constraints? - Mailing list pgsql-general

From BillR
Subject Re: R: One column to multiple columns based on constraints?
Date
Msg-id 004a01caaa01$7b92ade0$72b809a0$@com
Whole thread Raw
In response to Re: R: One column to multiple columns based on constraints?  ("Davor J." <DavorJ@live.com>)
List pgsql-general

Is there any reason it has to be done in one DML statement? Can you write a procedure to this in multiple steps?

 

BillR

 

From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Davor J.
Sent: February-09-10 2:02 PM
To: pgsql-general@postgresql.org
Subject: Re: [GENERAL] R: One column to multiple columns based on constraints?

 

Crosstab is indeed very interesting. Thank you for the suggestion Vincenzo.

 

regards

Davor

Look for crosstab in the documentation.

Il giorno 8 feb, 2010 8:21 p., "Davor J." <DavorJ@live.com> ha scritto:

Let's say you have a table:
CREATE TABLE t (
time date,
data integer
)

Suppose you want a new table that has columns similar to the following:
"(x.time, x.data, y.time, y.data, z.time, z.data)" where x.time, y.time and
z.time columns are constrained (for example x.time >2007  AND x.time <2008,
y.time >2008 AND y.time < 2009, z.time > 2010)

How would you do this. Note that you can not use JOIN as there is no
relationship.

Currently I came up with something like this:

SELECT X.*, (SELECT Y.time, Y.data FROM t AS Y WHERE Y.time = X.time + 1),
(SELECT Z.time .) FROM t AS X WHERE  X.time >2007  AND X.time <2008

But it's somewhat awkward. I thought maybe someone has better idea's. Any
input is welcome.



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