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From: James Orr <james@orrwhat.net>
To: Tim Perdue <tim@perdue.net>, Larry Rosenman <ler@lerctr.org>
Subject: Re: [SQL] Latitude / Longitude
Date: Thu, 12 Sep 2002 18:10:01 -0400
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On Thursday 12 September 2002 15:49, Tim Perdue wrote:
> On Thu, Sep 12, 2002 at 12:49:21PM -0500, Larry Rosenman wrote:
> > Look at contrib/earthdistance, I **think** it does what you need.
>
> Thanks, yeah this starts to get me into the realm of what I need. It still
> has to run every possible permutation to figure out which one is closest
> for each postalcode. What I'll do is run that once and build a 3rd table
> which can be used to join the other two together using a view.

If you are looking for everything within a certain radius of a zip code, what 
I have done in the past is calculate the highest/lowest longitude and 
latitude and then select anything that falls between them and only check 
those ones to see if they fall within the radius.

That's saves a lot of time over checking the exact distance for every zip 
code.

- James