Natural Join

Question

What will be the output of Natural Join if there is(are) common attribute(s) in two relations but no common value in these common attribute(s) ?

for example

Table R

A	B
6	9
7	1

Table S

B	C
7	3
5	8

R Natural Join s will be ? 

Answer 1

Empty set if no common value.

Cartesian Product if no common attribute.