You may need to check address fields (for example) for a NULL value or an empty string (the value looks null, but simply contains an empty string – which is still technically a value).

The query below checks for null values, as well as empty strings, then provides a suitable replacement on either occasion.

SELECT  TABLE.ID,             ISNULL(NULLIF(TABLE.Address, ''), 'No Address') [Address]    FROM    [dbo].[TABLE]