mysql计算经纬度距离function

DELIMITER $$

CREATE DEFINER=`root`@`localhost` FUNCTION `lat_long_distance`(in_lat1 DOUBLE, in_long1 DOUBLE, in_lat2 DOUBLE, in_long2 DOUBLE) RETURNS double
BEGIN
    DECLARE Distance DOUBLE;

    DECLARE RadLatBegin DOUBLE;
    DECLARE RadLatEnd DOUBLE;
    DECLARE RadLatDiff DOUBLE;
    DECLARE RadLngDiff DOUBLE;

    DECLARE EARTH_RADIUS DOUBLE;
    SET EARTH_RADIUS = 6378.137;

    SET RadLatBegin = in_lat1 *PI()/ 180.0 ;
    SET RadLatEnd = in_lat2 *PI()/ 180.0 ;
    SET RadLatDiff = RadLatBegin - RadLatEnd;
    SET RadLngDiff = in_long1 *PI()/ 180.0 - in_long2 *PI()/ 180.0 ;
    SET DISTANCE = 2 *ASIN(
               SQRT(
                   POWER(SIN(RadLatDiff / 2), 2)+COS(RadLatBegin)*COS(RadLatEnd)
                   *POWER(SIN(RadLngDiff / 2), 2)
               )
           );

    SET Distance = Distance * EARTH_RADIUS;
RETURN DISTANCE;
END