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Apply proper sql.sgml change.

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This commit is contained in:
Bruce Momjian 2001-01-09 16:05:21 +00:00
parent 777137b7a9
commit f906597e50
1 changed files with 42 additions and 42 deletions
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84
doc/src/sgml/sql.sgml
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@ -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>