Message-ID: <429DDBB1.7000204@skynet.be>
Date: Wed, 01 Jun 2005 18:00:49 +0200
From: Alain Reymond <arwebmail@skynet.be>
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To: pgsql-sql@postgresql.org
Subject: How do write a query...
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Hello,

I have the following problem :

I have a table like
Id    Num      Date                   AValue
1      10         01/01/2005       50
2      10         31/05/2005       60
3      25         02/02/2005       55
4      25         15/03/2005       43
5      25         28/05/2005       62
etc..

Id is unique, Num is an identification number with duplicates possible,
date is a ... date and Avalue... a value!

If we have
Id    Num      Date                   AValue
Id1  Num1    Date1                  AValue1
Id2  Num1    Date2                  AValue2

The table is ordered on Num+Date.
What I would like to calculate is (AValue2-AValue1) for a given Num
(here num1).

In this case, I would have to calculate
60-50 for Num 10
and
43-55, 62-43 for Num 25.

Do you have any idea if it can be done simply with a request...

I thank you

Regards.

Alain Reymond