--
-- This routine calculates the distance between two points (given the
-- latitude/longitude of those points). It is being used to calculate
-- the distance between two locations using GeoDataSource (TM) products
--
-- Calculate distance between two points lat1, long1 and lat2, long2
-- Uses radius of earth in kilometers or miles as an argurments
--
-- Typical radius:  3963.0 (miles) (Default if no value specified)
--                  6387.7 (km)
--
--
-- For enquiries, please contact sales@geodatasource.com
-- Official Web site: https://www.geodatasource.com
--
-- Thanks to Janes Swarowski for contributing the source code.
--
-- GeoDataSource.com (C) All Rights Reserved 2022
--


create function dbo.Distance( @lat1 float , @long1 float , @lat2 float , @long2 float)
returns float

as

begin

declare @DegToRad as float
declare @Ans as float
declare @Miles as float

set @DegToRad = 57.29577951
set @Ans = 0
set @Miles = 0

if @lat1 is null or @lat1 = 0 or @long1 is null or @long1 = 0 or @lat2 is
null or @lat2 = 0 or @long2 is null or @long2 = 0 or (@lat1 = @lat2 and @long1 = @long2)

begin

return ( @Miles )

end

set @Ans = SIN(@lat1 / @DegToRad) * SIN(@lat2 / @DegToRad) + COS(@lat1 / @DegToRad ) * COS( @lat2 / @DegToRad ) * COS(ABS(@long2 - @long1 )/@DegToRad)

set @Miles = 3959 * ATAN(SQRT(1 - SQUARE(@Ans)) / @Ans)

set @Miles = CEILING(@Miles)

return ( @Miles )

end