Difference between table level and column level NOT NULL constraint?

Hi,

What is the difference between table level and column level NOT NULL constraint?

for e.g.a not null constraint can be defined in the foll ways

1)

Create table test
(testnull VARCHAR2(10) NOT NULL)

2)

Create table test
(testnull VARCHAR2(10));

ALTER TABLE ADD CHECK (testnull NOT NULL);

Is there any difference in the way Oracle does validation for the above defined constraint methods or are there any performance differences?

Thanx in advance.

regards,
Pradeep

(Pls cc ur response to : pradeep.mittal_at_iflexsolutions.com)
Received on Fri Feb 22 2002 - 11:08:53 CST