From fd33f237d27745ea307a22c35713547e35907580 Mon Sep 17 00:00:00 2001
From: asfernandes <asfernandes@users.sourceforge.net>
Date: Thu, 3 May 2007 01:32:08 +0000
Subject: [PATCH] Doc. for new join types

---
 doc/sql.extensions/README.joins.txt | 38 +++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 doc/sql.extensions/README.joins.txt

diff --git a/doc/sql.extensions/README.joins.txt b/doc/sql.extensions/README.joins.txt
new file mode 100644
index 0000000000..95d1e4d412
--- /dev/null
+++ b/doc/sql.extensions/README.joins.txt
@@ -0,0 +1,38 @@
+--------------
+New JOIN types
+--------------
+
+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;