http://docs.oracle.com/javadb/10.8.3.0/ref/rrefsqljnaturaljoin.html

It offers a further specialization of equi-joins. The join predicate arises implicitly by comparing all columns in both tables that have the same column-name in the joined tables. The resulting joined table contains only one column for each pair of equally-named columns. Example - SELECT * FROM Vendor NATURAL JOIN advance