plpgsql locate provider by zip code

I spent the last 15 hours writing this function. It took me all day to
figure it out. This is my first postgresql function.

I have a zip code database (the free one). I wanted to locate providers
by zip code, and also have the distance to each provider. I had a PHP
script that did this well, but I needed to move it into the database to
make it easy for the IVR system. This is what I did:

/* My database of zips */
CREATE TABLE "zips" (
"zip" int8 NOT NULL,
"state" char(2) DEFAULT 'NA' NOT NULL,
"city" varchar(50) DEFAULT 'NA' NOT NULL,
"location" point DEFAULT '(0,0)' NOT NULL -- (longitude,latitude)
);

/* Earthdistance from Postgresql contrib */
CREATE FUNCTION geo_distance (point, point) RETURNS float8
AS '/usr/local/pgsql/share/contrib/earthdistance.so' LANGUAGE 'c';

CREATE OPERATOR <@> (
leftarg = point,
rightarg = point,
procedure = geo_distance,
commutator = <@>
);

I figured out this query to select my providers:

/* get my location by zip */
select location from zips where zip=95661;

/* using my location get 10 providers */
select p.name, p.city, p.phone1, '(121.234,38.7346)'::point <@> location as distance
from zips z, providers p
where '(121.234,38.7346)'::point <@> location < 50
and z.zip = p.zip
order by distance
limit 10;

This worked well, now time to move it into the database:

create function locate_providers (int8,int2) returns text as '
declare
source_zip alias for $1;
offset alias for $2;
source_point point;
result record;
begin
-- Get the source point by zip
select into source_point location from zips where zip = source_zip;

if not found
then return ''Error: ZIP not found'';
end if;

-- Get the providers one at a time by offset
select into result
trim(p.name)::text as name, trim(p.address1)::text as address,
p.phone1::text as phone, trim(p.city)::text as city,
round(source_point <@> location)::text as distance
from zips z, providers p
where source_point <@> location < 50 and z.zip = p.zip
order by distance
limit 1, offset;

-- Return
if found
then return result.name || '', '' || result.address || '', '' ||
result.city || '', '' || result.phone || '', '' ||
result.distance || '' Miles'';
end if;

-- if nothing found
return ''Error: Provider Not Found'';
end;'
language 'plpgsql';

Now I could issue:

select locate_providers(95661,0);
select locate_providers(95661,1);
select locate_providers(95661,2);
...
select locate_providers(95661,10);

and get back each provider by distance.

It works well for me, probably a few things wrong with it, but I'm a
novice! 8-) I hope this helps some of the people out there trying to
figure out this stuff.

--
_ | _
(_()(|('.|)('||.|()|`|(