SQL Function: Distance in kilo meters between two Geo Points

gistfile1.txt

CREATE FUNCTION `GEO_DISTANCE_KM`(point1 POINT, point2 POINT) RETURNS NUMERIC
RETURN 6371 * acos(
      cos(radians(X(point2)))
      * cos(radians(X(point1)))
      * cos(radians(Y(point1)) - radians(Y(point2)))
      + sin(radians(X(point2)))
      * sin(radians(X(point1))) 
      );