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New JOIN types
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Author:
Adriano dos Santos Fernandes <adrianosf@uol.com.br>

Format:
<named columns join> ::=
<table reference> <join type> JOIN <table reference> USING ( <column list> )

<natural join> ::=
<table reference> NATURAL <join type> JOIN <table primary>

Notes:
Named columns join:
1) All columns specified in <column list> should exist in the tables of both sides.
2) An equi-join (<left table>.<column> = <right table>.<column>) is automatically
created for all columns (ANDed).
3) The USING columns can be accessed without qualifier, and in this case, result of
it is COALESCE(<left table>.<column>, <right table>.<column>).
4) In "SELECT *", USING columns are expanded once, using the above rule.

Natural join:
1) A "named columns join" is automatically created with all columns common to the
left and right tables.
2) If the is no common column, a CROSS JOIN is created.

Examples:
1) select *
from employee
join department
using (dept_no);

2) select *
from employee_project
natural join employee
natural join project;