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Make subquery aliases optional in the FROM clause.

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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
This commit is contained in:
Dean Rasheed
2022-07-20 09:29:42 +01:00
parent 1caf915ff3
commit bcedd8f5fc
10 changed files with 164 additions and 81 deletions
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16
doc/src/sgml/ref/select.sgml
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@ -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>