Substitute a Value for NULLs

Use the isnull built-in function to substitute a particular value for nulls. The substitution is made only for display purposes; actual column values are not affected.

The syntax is:
isnull(expression, value) 

For example, use the following statement to select all the rows from titles, and display all the null values in column notes with the value unknown.

select isnull(notes, "unknown") 
from titles