Not sure how I see how using Nulls violates data integrity. If your point is that if 0 is an appropriate value when there is not another valid data choice, then yes, the field should be set to NOT NULL with a default value of 0. That is not always the case. I don't need to reiterate the several discussions that have preceeded this, other than to say that the use of NULLS does not automatically violate data integrity.