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References: <49CA6121.8090704@vivawasser.de> <49CCC24A.90800@vivawasser.de>
Date: Wed, 1 Apr 2009 07:57:57 -0700
Message-ID: <5d0f60990904010757r34294c99y96fae71cc5579415@mail.gmail.com>
Subject: Re: Add: Special sort querstion
From: Dirk Jagdmann <jagdmann@gmail.com>
To: d.piekarski@vivawasser.de
Cc: pgsql-sql@postgresql.org
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I think it can not be done with default PostgreSQL functions and
operators, because you must compare two different columns of two rows
depending which row is on either side of the "<" comparision.

But I think you can do this with the following steps:

1) create a new type as a 4-tupel of start_lat, end_lat, start_lng, end_lng.
2) write a comparison function for this type
3) write a SQL-Function to convert 4 values into your new type (for
example: ToMyType(start_lat, end_lat, start_lnd, end_lng) returns
MyType...)
4) use ToMyType in the order clause of your select

If this would work, I'm interested in a working example code :-)

-- 
---> Dirk Jagdmann
----> http://cubic.org/~doj
-----> http://llg.cubic.org