That's just plain wrong. You need some value to populate optional fields, and NULL is a pretty decent choice to indicate that a string, date or number has not b

That's just plain wrong. You need some value to populate optional fields, and NULL is a pretty decent choice to indicate that a string, date or number has not been filled in. If you try to fix that by having special string or numeric constants, you're just making life harder, especially when you export the data. The poor souls that import it will think "hey, this timestamp says 1-1-1970, so this probably happened at Jan. 1, 1970."