Add Null and string in sql server 2000

Function for adding Null and string :SET CONCAT_NULL_YIELDS_NULL { ON OFF }
When SET CONCAT_NULL_YIELDS_NULL is ON, concatenating a null value with a string yields a NULL result.

CONCAT_NULL_YIELDS_NULL is OFF, concatenating a null value with a string yields the string itself .

SET CONCAT_NULL_YIELDS_NULL OFF

Select ' ' +'Ajay'

Result :Ajay

SET CONCAT_NULL_YIELDS_NULL ON

Select ' ' +'Ajay'
Result :NULL