Space used by nulls in database

Question

If a column is null, does that affect the space used by the column? Is the space used fixed by the column definition? Does this vary from database to database. (I am mainly

Answer 1

The number of bytes used by the row is smaller if you are using varchar or nvarchar datatypes. This is why you can create a table (but shouldn't) that has more potential bytes than can actually be stored in a record.