Documentation Source Text

       of collation sequence and affinity precedence.

       <p>^For each pair of columns identified by a USING clause, the column
       from the right-hand dataset is omitted from the joined dataset. ^This 
       is the only difference between a USING clause and its equivalent ON
       constraint.

  <li> <p>^(If the join-op is a "LEFT JOIN" or "LEFT OUTER JOIN", then the
       composite dataset is created as for an "INNER JOIN". Except, after
       the ON or USING filtering clauses have been applied, an extra row is 
       added to the output for each row in the original left-hand input 
       dataset (if any) that corresponds to no rows at all in the composite
       dataset.)^ ^The added rows contain NULL values in the columns that would
       normally contain values copied from the right-hand input dataset.

  <li> <p>^(If the NATURAL keyword is added to any of the join-ops, then an
       implicit USING clause is added to the join-constraints. The implicit
       USING clause contains each of the column names that appear in both
       the left and right-hand input datasets.)^ ^If the left and right-hand
       input datasets feature no common column names, then the NATURAL keyword
       has no effect on the results of the join. ^A USING or ON clause may
       not be added to a join that specifies the NATURAL keyword.
</ul>

<p>^(When more than two tables are joined together as part of a FROM clause,
the join operations are processed in order from left to right. In other 
words, the FROM clause (A join-op-1 B join-op-2 C) is processed as 
((A join-op-1 B) join-op-2 C).)^