• NATURAL JOIN - Works only when the two tables have a single identical named and type column as the joining key.
  • NATURAL JOIN is nearly the same as INNER JOIN except that repeated column is avoided.
  • When using NATURAL JOIN, the ON and USING keywords should not be allowed, even for some system you can.
  • Not every RDBMS has implemented NATURAL JOIN.
  • A skeleton version of NATURAL JOIN syntax is this:
    SELECT select_list
    FROM table_1 
    NATURAL JOIN table_2
    [WHERE search_conditions ]
    [ORDER BY column1, column2, ... ]
    Example using NATURAL JOIN between the tables:
    SQL server does not support NATURAL JOIN.
    MySQL, Oracle, PostgreSQL :
    Select First_name "First name",
      Last_name "Last name",
      email, Telephone_type "Phone type",
      Telephone_number as "Phone number"
     from customers 
     NATURAL JOIN telephones 
     WHERE  Telephone_type<>'Unknown'
     order by Last_name;
    The result should be:
    First name Last name email Phone type Phone number
    Judith Bowman J.Bowman@imb.com Cell (371) 153-54
    Judith Bowman J.Bowman@imb.com Work (371) 143-54
    Ricard Nixon Ricard.Nixon@hotmail.com Work (978) 667-94
    Ricard Nixon Ricard.Nixon@hotmail.com Home (978) 667-94
    Robert Redford R.Redford@google.com Home (679) 234-94
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