From bcedd8f5fce0b69970cf0cee7bca560833d05869 Mon Sep 17 00:00:00 2001
From: Dean Rasheed <dean.a.rasheed@gmail.com>
Date: Wed, 20 Jul 2022 09:29:42 +0100
Subject: Make subquery aliases optional in the FROM clause.

This allows aliases for sub-SELECTs and VALUES clauses in the FROM
clause to be omitted.

This is an extension of the SQL standard, supported by some other
database systems, and so eases the transition from such systems, as
well as removing the minor inconvenience caused by requiring these
aliases.

Patch by me, reviewed by Tom Lane.

Discussion: https://postgr.es/m/CAEZATCUCGCf82=hxd9N5n6xGHPyYpQnxW8HneeH+uP7yNALkWA@mail.gmail.com
---
 doc/src/sgml/ref/select.sgml | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

(limited to 'doc/src')

diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 80bb8adcacc..410c80e730b 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -51,7 +51,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
     [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
                 [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ]
-    [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
+    [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
                 [ WITH ORDINALITY ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
@@ -490,8 +490,8 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
         output were created as a temporary table for the duration of
         this single <command>SELECT</command> command.  Note that the
         sub-<command>SELECT</command> must be surrounded by
-        parentheses, and an alias <emphasis>must</emphasis> be
-        provided for it.  A
+        parentheses, and an alias can be provided in the same way as for a
+        table.  A
         <link linkend="sql-values"><command>VALUES</command></link> command
         can also be used here.
        </para>
@@ -2041,6 +2041,16 @@ SELECT 2+2;
    </para>
   </refsect2>
 
+  <refsect2>
+   <title>Omitting sub-<command>SELECT</command> aliases in <literal>FROM</literal></title>
+
+   <para>
+    According to the SQL standard, a sub-<command>SELECT</command> in the
+    <literal>FROM</literal> list must have an alias.  In
+    <productname>PostgreSQL</productname>, this alias may be omitted.
+   </para>
+  </refsect2>
+
   <refsect2>
    <title><literal>ONLY</literal> and Inheritance</title>
 
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