Heikki Simperi schrieb:
> What should happend in theory when two tables are joined by natural and they
> do not have columns with same name?
>
>
> A (a,b,c)
> B (d,e)
>
> A |><| B
>
>
> Cartesian or empty or error?
>
>
>
> Heikki Simperi
>
>
Since the natural join can be defined as a restricted catesian product,
where the restriction is the equality condition on the join attributes
and where the second set of join attributes is "projected away" after
restriction, you obviously have a cartesian product when there are no
common columns. Besides, "errors" will never be a result of a relational
operation, because every relational operator returns again a relation.
Greetings,
Andreas
Received on Thu Sep 01 2005 - 12:58:05 CDT
