--'=================================================================================
--' Distance Calculator
--'=================================================================================
--' This function calculates the distance between two latitude/logitude
--' coordinates. Disance can be returned as Kilometers or Miles.
--'
--' This function was designed for Microsoft SQL Server 2005
--'
--' Accepts:
--'	Lat1 = Latitude of point one (decimal, required)
--'	Lon1 = Longitude of point one (decimal, required)
--'	Lat2 = Latitude of point two (decimal, required)
--'	Lon2 = Longitude of point two (decimal, required)
--
--'
--' Provided by: http://www.zip-codes.com
--'
--' © 2005 Zip-Codes.com, All Rights Reserved
--'=================================================================================

CREATE function [Distance]( @lat1 decimal(12, 6) , @long1 decimal(12, 6) , @lat2 decimal(12, 6) , @long2 decimal(12, 6)) 
returns decimal(12,2)

as

begin

if @lat1 = @lat2 and @long1 = @long2
begin
	return 0
end 

declare @DegToRad as float
declare @Ans as float
declare @Miles as decimal(12,2)

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

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)

return ( @Miles )

end