Rune Bivrin (9/24/2010)
However, looking the table in the question I'd probably remove the NULL-ability on the cell phone numbers. Nullable VARCHAR often doesn't make sense. Particularly when they are entered in a classic GUI. How do you diffrentiate between a NULL phone number and a zero-length phone number?
Surely in this case, an empty string means that they don't have a cell phone, NULL means you don't know whether they have or not.