Re: key constraint

Jian Xu wrote:
> i'm doing a database project, and met one question about the key
> constraints. what the question asked is simply " Drop key constraint
> from the table Cust_Order relation." i just dropped the primary key
> constraint for that relation, but i'm confused with the "not null"
> constraint. do i need to drop that constraint also?

Not neccesarily. The question is why you are dropping the key constraint. Is it for efficiency reasons or did you make a conceptual mistake in your data model? In the first case the not-null should definitely stay, in the second case you simply have to rethink if they may be null or not.

-- 
  Jan Hidders