SET CONCAT_NULL_YIELDS_NULL ON

DECLARE @STR AS VARCHAR(8)

SET @STR = 'abcdefghij'

SELECT @STR

SELECT LEN(@str)

SELECT LEN(@str+NULL)

SELECT ISNULL(@str+NULL,'1234567890')

--------

abcdefgh

-----------

8

-----------

NULL

---------

123456789

Okay.....