Lukas Eder has a comprehensive guide to joining data using SQL:
Alternative syntaxes: NATURAL JOIN
An more extreme and much less useful form of
"EQUI" JOIN is the
NATURAL JOIN clause. The previous example could be further “improved” by replacing
NATURAL JOIN like this:
NATURAL JOIN film_actor
NATURAL JOIN film
Notice how we no longer need to specify any
JOIN criteria, because a
NATURAL JOIN will automatically take all the columns that share the same name from both tables that it joins and place them in a “hidden”
USING clause. As we’ve seen before, as primary keys and foreign keys have the same column name, this appears quite useful.
There is a high likelihood that you will learn at least one new thing here; for example, check out lateral joins (which SQL Server practitioners know as something else).