How to return default value from SQL query

Is there any easy way to return single scalar or default value if query doesn’t return any row?

At this moment I have something like this code example:

IF (EXISTS (SELECT * FROM Users WHERE Id = @UserId))  
    SELECT Name FROM Users WHERE Id = @UserId  
ELSE
    --default value
    SELECT 'John Doe'

How to do that in better way without using IF-ELSE?

Answer

Assuming the name is not nullable and that Id is unique so can match at most one row.

 SELECT 
    ISNULL(MAX(Name),'John Doe')
 FROM 
    Users 
 WHERE 
    Id = @UserId