SQL 计算两个地理坐标相差的距离的函数

Create function getGreatCircleDistance(@lat1 decimal(18,11),@lng1 decimal(18,11),@lat2 decimal(18,11),@lng2 decimal(18,11))
returns float
as
begin
declare @EARTH_RADIUS decimal(18,1);
declare @radLat1 float;
declare @radLat2 float;
declare @a float;
declare @b float;
declare @s float;
set @EARTH_RADIUS=6378137.0;
set @radLat1= @lat1 * PI() / 180.0;
set @radLat2=@lat2 * PI() / 180.0;
set @a = @radLat1 - @radLat2;
set @b = @lng1 * PI() / 180.0 - @lng2 * PI() / 180.0;

set @s = 2 * asin(sqrt(power(sin(@a / 2), 2) + cos(@radLat1) * cos(@radLat2) * power(sin(@b / 2), 2)));
set @s = @s * @EARTH_RADIUS;
-- set @s = round(@s * 10000,2) / 10000.0;
set @s = round(@s ,2);
return @s;
end