MySQL function to determine the distance between two points considering Earth's spherical surface.

DISTANCE.SQL

DELIMITER $$
-- Returns value in Km (Kilometers)
CREATE FUNCTION distance_points (lat1 FLOAT, lng1 FLOAT, lat2 FLOAT, lng2 FLOAT)
    RETURNS FLOAT
    DETERMINISTIC
    BEGIN
        RETURN (acos(sin(radians(lat1)) * sin(radians(lat2)) + 
				cos(radians(lat1)) * cos(radians(lat2)) * 
				cos(radians(lng1) - radians(lng2))) * 6371);
    END$$