JOIN (Natural join)

Question

In a natural join, the common attribute occur only once, 

but in join

https://gateoverflow.in/3718/gate2004-it-74

Select * from Student, Department

in this common, attribute we have given m+n

I tried in w3 schools

https://www.w3schools.com/sql/sql_join.asp

SELECT *
FROM Orders, Customers
WHERE City='Berlin' AND OrderID = '10248'

here common attribute is occuring only once, 

PLease guide .

Comments

In natural join the common attributes occurs only once because The two column data are exactly same but in cross product this is not the case the two column may or may not contain exactly same data.