At 10:47 PM 30/03/2006, you wrote:

>I think the "integer check(value>0)" is not allowed.

Not true.

>If you write "CANTIDAD INTEGER NOT NULL" the value must be greater
>then null or 0

No. NOT NULL means the value can not be null.

>At Integer there is no difference between null and 0.

Wrong. Null is not a value, it is a state. Zero is a value.

./hb