SQL: Sort by distance from a point

distance.sql

# Adapted from: http://dillieodigital.wordpress.com/2011/06/16/sorting-latitudelongitude-positions-by-distance-in-sql/
SELECT
	*, 6378 * 2 * ASIN(
		SQRT(
			POWER(
				SIN((51.5081 - latitude) * pi() / 180 / 2),
				2
			) + COS(51.5081 * pi() / 180) * COS(latitude * pi() / 180) * POWER(
				SIN((0.1281 - longitude) * pi() / 180 / 2),
				2
			)
		)
	) AS distance_km
FROM
	my_table
ORDER BY
	distance_km;
	# PostgreSQL: distance_km ASC NULLS LAST;
	# MySQL: -distance_km DESC;