DELIMITER //
CREATE FUNCTION DISTANCE(lat1 DOUBLE, lng1 DOUBLE, lat2 DOUBLE, lng2 DOUBLE)
RETURNS DOUBLE
BEGIN
    DECLARE deltaLng, cosLat1, cosLat2, sinLat1, sinLat2, cosDeltaLng, sinDeltaLng, y1, y2, x1, x2, x, y, R DOUBLE;
    SET R=6372795;
    SET lat1 = lat1*0.017453292519943295769;
    SET lng1 = lng1*0.017453292519943295769;
    SET lat2 = lat2*0.017453292519943295769;
    SET lng2 = lng2*0.017453292519943295769;
    SET deltaLng = ABS(lng2-lng1);
    SET cosLat1 = COS(lat1);
    SET cosLat2 = COS(lat2);
    SET sinLat1 = SIN(lat1);
    SET sinLat2 = SIN(lat2);
    SET cosDeltaLng = COS(deltaLng);
    SET sinDeltaLng = SIN(deltaLng);
    SET y1 = cosLat2*sinDeltaLng;
    SET y2 = cosLat1*sinLat2-sinLat1*cosLat2*cosDeltaLng;
    SET y = SQRT(y1*y1+y2*y2);
    SET x1 = sinLat1*sinLat2;
    SET x2 = cosLat1*cosLat2*cosDeltaLng;
    SET x = x1 + x2;
    RETURN ATAN2(y,x)*R;
END //