It depends on where the NULL column is in the set of columns for the table. If the NULL column is in the middle of the table and is followed by other non-NULL columns, then it takes one byte of storage (the length indicator). If it is the last column of the table, or if all following columns are null, then it (and any following columns) takes zero bytes.
Originally posted by gandolf989 There is this wonderful tool called tahiti.oracle.com. It contains all of the documentation that you should need. In fact I was able to find out about nulls is about 30 seconds. You should avail yourself of all of the resources out there.
And quit starting second threads like "I'm waiting." As people volunteer their time, there should be no expectation of urgency on getting any kind of response.