CHECKSUM and OPTION(RECOMPILE)

Working with CHECKSUM

functions, I encountered a situation

when the result of the

CHECKSUM function is

effected by OPTION(RECOMPILE)

Please see following example:




DECLARE @a VARCHAR(5),@b VARCHAR(5)
SET @a='a'
SET @b='b'

SELECT CHECKSUM(@a,@b) as Result

SELECT CHECKSUM(@b,@a) as Result

 

SELECT CHECKSUM(@a,@b) as Result
OPTION(RECOMPILE)

As you can see the result of CHECKSUM(@a,@b) without recompile
and with recompile is different, when using option(recompile)
we see that SQL Server change the order of the variables.

Do you know why?
If yes, Please leave comments.