Apply proper sql.sgml change.

diff --git a/doc/src/sgml/sql.sgml b/doc/src/sgml/sql.sgml
index 6f0e4dcb21e89c170a2d4e09b2e3d4d679cfe21b..5a2ce9ab015c935810d0ada236482af1ce3517d3 100644 (file)
--- a/doc/src/sgml/sql.sgml
+++ b/doc/src/sgml/sql.sgml
@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/sql.sgml,v 1.16 2001/01/09 15:48:18 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/sql.sgml,v 1.17 2001/01/09 16:05:21 momjian Exp $
 -->
 
  <chapter id="sql">
@@ -1058,10 +1058,20 @@ select sname, pname from supplier
         item that occurs in a FROM clause and before any WHERE, GROUP BY,
         or HAVING clause.  Other table references, including table names or
         other JOIN clauses, may be included in the FROM clause if separated
-        by commas.  A JOIN of two tables is logically like any other
-        table listed in the FROM clause.  A JOINed table can only be JOINed
-        to additional tables in a Qualified JOIN as indicated by the
-        elipses below.
+        by commas.  JOINed tables are logically like any other
+        table listed in the FROM clause.
+        </para>
+
+        <para>
+        JOINs of all types can be chained together or nested where either or both of
+        <replaceable class="parameter">T1</replaceable> and
+        <replaceable class="parameter">T2</replaceable> may be JOINed tables.
+        A Qualified JOIN may be JOINed to another table (or JOINed table)
+        following its join specification, which consists of either an
+        ON <replaceable>search condition</replaceable> or
+        USING ( <replaceable>join column list</replaceable> ) clause.
+        Parenthesis can be used around JOIN clauses to control the order
+        of JOINs which are otherwise processed left to right.
         </para>
 
     <variablelist>
@@ -1081,37 +1091,35 @@ select sname, pname from supplier
                        respectively, and returns a joined table containing a cross
                        product, NxM, of joined rows. For each row R1 of T1, each row
                        R2 of T2 is joined with R1 to yield a joined table row JR
-                       consisting of all fields in R1 and R2.
+                       consisting of all fields in R1 and R2. A CROSS JOIN is
+                       essentially an INNER JOIN ON TRUE.
                        </para>
                        </listitem>
                </varlistentry>
 
                <varlistentry>
-                   <term>Qualified JOINs</term>                        
+                   <term>Qualified JOINs</term>
                    <listitem>
+
                        <cmdsynopsis>
                                <arg choice="req"> <replaceable class="parameter">T1</replaceable> </arg>
-                               <arg>
-                                       <group>
-                                       <arg choice="plain"> INNER </arg>
+                               <group choice="opt">
+                                       <arg choice="opt"> INNER </arg>
                                        <arg>
-                                               <group>
-                                               <arg> LEFT </arg>
-                                               <arg> RIGHT </arg>
-                                               <arg> FULL </arg>
+                                               <group choice="req">
+                                                       <arg choice="plain"> LEFT </arg>
+                                                       <arg choice="plain"> RIGHT </arg>
+                                                       <arg choice="plain"> FULL </arg>
                                                </group>
-                                               <arg> OUTER </arg>
+                                               <arg choice="opt"> OUTER </arg>
                                </arg>
-                                       </group>
-                       </arg>
+                       </group>
                                <command> JOIN </command>
                                <arg choice="req"> <replaceable class="parameter">T2</replaceable> </arg>
-                               <arg choice="req">
-                                       <group>
+                               <group choice="req">
                                        <arg> ON <replaceable>search condition</replaceable></arg>
                                        <arg> USING ( <replaceable>join column list</replaceable> ) </arg>
-                                       </group>
-                               </arg>
+                               </group>
                                <arg choice="plain"> ... </arg>
                        </cmdsynopsis>
 
@@ -1122,9 +1130,6 @@ select sname, pname from supplier
                        column names, which the joined tables must have in common, and joins
                        the tables on those columns, resulting in a joined table having one
                        column for each common column and all of the other columns from both tables.
-                       Like all SELECT queries, the <replaceable>select list</replaceable> of the
-                       SELECT query, before the FROM clause, decides which columns from the joined
-                       table are in the result table returned.
                        </para>
 
                        <!-- begin join semantics -->
@@ -1226,23 +1231,22 @@ select sname, pname from supplier
                <varlistentry>
                    <term>NATURAL JOINs</term>
                <listitem>
+
                        <cmdsynopsis>
                                <arg choice="req"> <replaceable class="parameter">T1</replaceable> </arg>
-                               <arg>
-                                       <arg choice="plain"> NATURAL </arg>
-                                       <group>
-                                       <arg choice="plain"> INNER </arg>
+                               <arg choice="plain"> NATURAL </arg>
+                               <group choice="opt">
+                                       <arg choice="opt"> INNER </arg>
                                        <arg>
-                                               <group>
-                                               <arg> LEFT </arg>
-                                               <arg> RIGHT </arg>
-                                               <arg> FULL </arg>
+                                               <group choice="req">
+                                                       <arg choice="plain"> LEFT </arg>
+                                                       <arg choice="plain"> RIGHT </arg>
+                                                       <arg choice="plain"> FULL </arg>
                                                </group>
-                                               <arg> OUTER </arg>
+                                               <arg choice="opt"> OUTER </arg>
                                </arg>
-                                       </group>
-                       </arg>
-                               <command> JOIN </command>
+                       </group>
+                               <command> JOIN </command>                               
                                <arg choice="req"> <replaceable class="parameter">T2</replaceable> </arg>
                        </cmdsynopsis>
 
@@ -1250,18 +1254,14 @@ select sname, pname from supplier
                        A natural join creates a joined table where every pair of matching
                        column names between the two tables are merged into one column. The
                        join specification is effectively a USING clause containing all the
-            common column names and is otherwise like a Qualified JOIN except
-                       additional JOINs to the JOINed table are not permitted.
+            common column names and is otherwise like a Qualified JOIN.
                        </para>
                        </listitem>
                </varlistentry>
 
-               <varlistentry>
-                   <term>UNION JOIN</term>
-                   <listitem><para>Deprecated.</para></listitem>
-               </varlistentry>
         </variablelist>
 
+
     </sect3>
 
     <sect3>