An extension to the ANSI/ISO SQL standard is that you can specify views or derived tables on either side of a natural join. In the following statement:

SELECT *
FROM View1 NATURAL JOIN View2;

the columns in View1 are compared to the columns in View2. If, for example, a column called EmployeeID is found to occur in both views, and there are no other columns that have identical names, then the generated join condition is (View1.EmployeeID = View2.EmployeeID).

 Example

CREATE VIEW V(x) AS
SELECT R.y + 1
FROM R;

SELECT *
FROM V NATURAL JOIN (SELECT P.y FROM P) as T(x);

SELECT *
FROM V JOIN (SELECT P.y FROM P) as T(x) ON (V.x = T.x);