Calculate distance in SQL Server based on map latitude and longitude

Baked from somewhere else, you try it out, you can calculate it, but the correct is not quite understand.

Use [Niaoren]
GO
/****** object:userdefinedfunction [dbo].    [Fngetdistance] Script DATE:2017/7/28 Friday 12:17:56 ******/
SET ANSI_NULLS on
GO
SET QUOTED_IDENTIFIER ON
GO
--Calculates the distance between two coordinate points (longitude, latitude) of the Earth SQL function
--lordbaby
--Finishing: www.aspbc.com
ALTER FUNCTION [dbo]. [Fngetdistance] (@LatBegin Real, @LngBegin Real, @LatEnd Real, @LngEnd Real) RETURNS FLOAT
As
BEGIN
--distance (km)
DECLARE @Distance REAL
DECLARE @EARTH_RADIUS REAL
SET @EARTH_RADIUS = 6378.137-Earth radius
DECLARE @RadLatBegin Real, @RadLatEnd Real, @RadLatDiff real, @RadLngDiff Real
SET @RadLatBegin = @LatBegin *pi ()/180.0
SET @RadLatEnd = @LatEnd *pi ()/180.0
SET @RadLatDiff = @RadLatBegin-@RadLatEnd
SET @RadLngDiff = @LngBegin *pi ()/180.0-@LngEnd *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

Original address: http://www.open-open.com/code/view/1436452727411

Calculate distance in SQL Server based on map latitude and longitude