Case Sensitive String Compare User Function

-- CaseSensitiveCompare.udf
-- 
-- Author: Mark Howard
-- Date: 2/17/03

-- After reviewing the CaseCompare script submitted to SqlServerCentral.com by 
-- Mike McManus it seemed to me that a user defined function would be more useful.
-- This function is different in its approach to performing a case sensitive
-- compare, to the structure of the program, and in the values returned by the
-- function.  It is offered as an alternative method to Mikes's.
--
-- Returns: 
--    -1 if one or both of the string are null.
--     1 if the strings are equal
--     0 if the strings are not equal. 
-- Please feel free to copy, use, and change in any way.

create function CaseSensitiveCompare(@String1 varchar(1024), @String2 varchar(1024)) returns int
as
begin
    declare
        @CharPosition   int,
        @ReturnValue    int,
        @StringsLength  int
        
    -- Check that the string are not null.
    if @String1 is not null and @String2 is not null
    begin
        -- If the strings are equal in length then we can proceed to check each character.
        if (len(@String1) = len(@String2))
        begin
            -- Compare Strings one character at a time until string length is reached
            -- or until the positional characters are not equal.
            set @CharPosition = 1
            set @ReturnValue = 1
            -- Both strings are the same length so use String1 length.
            set @StringsLength = len(@String1)
            while ((@CharPosition <= @StringsLength) and @ReturnValue = 1)
            begin
                if ASCII(SubString(@String1, @CharPosition, 1)) != ASCII(SubString(@String2, @CharPosition, 1))
                    set @ReturnValue = 0
                set @CharPosition = @CharPosition + 1
            end
        end
        else
            -- The strings are not the same length, thus not equal.
            set @ReturnValue = 0
    end
    else
        -- One or both string are null.
        set @ReturnValue = -1
    return @ReturnValue
end
go

/*
Test Code Highlight and run once the function above is installed.

Declare
    @ReturnValue int

-- Test for equality.
set @ReturnValue = dbo.CaseSensitiveCompare('xyz', 'xyz')
Print convert(char(3), @ReturnValue)  

-- Test for inequality.
set @ReturnValue = dbo.CaseSensitiveCompare('xyz', 'Xyz')
Print convert(char(3), @ReturnValue)  

-- Test for inequality.
set @ReturnValue = dbo.CaseSensitiveCompare('xyz', 'xy')
Print convert(char(3), @ReturnValue)  

-- Test for nulls and inequality.
set @ReturnValue = dbo.CaseSensitiveCompare(null, null)
Print convert(char(3), @ReturnValue)  

-- Notice these different empty string are equal due to Sql trimming spaces.
set @ReturnValue = dbo.CaseSensitiveCompare('  ', '')
Print convert(char(3), @ReturnValue)  
*/