Get nearby zip codes from a certain zip code.

getNearbyZipCodes.sql

-- I think I fixed all of the bugs, but there may be one.
-- Now I just need to see about some optimization
SELECT 
	n.city,
	n.zip_code,
	n.latitude,
	n.longitude,
	3958.75587 * c AS distance
FROM (
	SELECT 	
		n.city,
		n.zip_code,
		n.latitude,
		n.longitude,
		2 * ATAN2( SQRT( n.a ), SQRT( 1 - n.a ) ) AS c
	FROM (
		SELECT 
			n.city,
			n.zip_code,
			n.latitude,
			n.longitude,
			SIN( n.dLat / 2 ) * SIN( n.dLat / 2 ) 
				+ COS( n.nRadLng ) * COS( n.oRadLng ) 
				* SIN( dLng/2 ) * SIN( dLng/2 ) AS a 
		FROM (
			SELECT
				n.city,
				n.zip_code,
				n.latitude,
				n.longitude,
				RADIANS( n.latitude - o.latitude ) AS dLat,
				RADIANS( n.longitude - o.longitude ) AS dLng,
				o.latitude,
				o.longitude,
				RADIANS( o.latitude ) AS oRadLat,
				RADIANS( o.longitude ) AS oRadLng,
				RADIANS( n.latitude ) AS nRadLat,
				RADIANS( n.longitude ) AS nRadLng
			FROM 
				iws_zip_codes n,
				( 
					SELECT
						o.latitude,
						o.longitude,
						o.latRange,
						o.lngRange,
						o.latitude - o.latRange AS minLat,
						o.latitude + o.latRange AS maxLat,
						o.longitude - o.lngRange AS minLng,
						o.longitude + o.lngRange AS maxLng
					FROM ( 
						SELECT
							o.latitude,
							o.longitude,
							5/69.172 AS latRange,
							ABS( 5 / ( COS( o.longitude ) * 69.172 ) ) AS lngRange
						FROM iws_zip_codes o
				        WHERE o.zip_code = 23505
					) o 
				) o
			WHERE n.latitude BETWEEN o.minLat AND o.maxLat
				AND n.longitude BETWEEN o.minLng AND o.maxLng
		) n
	) n
) n;