olaf_bredv wrote:

> I think the "integer check(value>0)" is not allowed.
> If you write "CANTIDAD INTEGER NOT NULL" the value must be greater
> then null or 0
> At Integer there is no difference between null and 0.

No, not quite. In SQL, integers are signed, so they can be
less that zero. More important, zero is not equivalent to null.
Null is a state that applies to a field where the value is
unknown. Not knowing how many euros you've got in your pocket
is different from knowing that you have none.

Regards,


Ann