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Allow AS to be omitted when specifying an output column name in SELECT

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(or RETURNING), but only when the output name is not any SQL keyword.
This seems as close as we can get to the standard's syntax without a
great deal of thrashing.  Original patch by Hiroshi Saito, amended by me.
This commit is contained in:
Tom Lane
2008-02-15 22:17:06 +00:00
parent cc80f0a340
commit e67867b26c
10 changed files with 119 additions and 51 deletions
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29
doc/src/sgml/queries.sgml
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@@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/queries.sgml,v 1.44 2007/02/01 19:10:24 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/queries.sgml,v 1.45 2008/02/15 22:17:06 tgl Exp $ -->
<chapter id="queries">
<title>Queries</title>
@@ -491,7 +491,7 @@ FROM <replaceable>table_reference</replaceable> AS <replaceable>alias</replaceab
<synopsis>
FROM <replaceable>table_reference</replaceable> <replaceable>alias</replaceable>
</synopsis>
The <literal>AS</literal> key word is noise.
The <literal>AS</literal> key word is optional noise.
<replaceable>alias</replaceable> can be any identifier.
</para>
@@ -1040,13 +1040,32 @@ SELECT a AS value, b + c AS sum FROM ...
</para>
<para>
If no output column name is specified using <literal>AS</>, the system assigns a
default name. For simple column references, this is the name of the
referenced column. For function
If no output column name is specified using <literal>AS</>,
the system assigns a default column name. For simple column references,
this is the name of the referenced column. For function
calls, this is the name of the function. For complex expressions,
the system will generate a generic name.
</para>
<para>
The <literal>AS</> keyword is optional, but only if the new column
name does not match any
<productname>PostgreSQL</productname> keyword (see <xref
linkend="sql-keywords-appendix">). To avoid an accidental match to
a keyword, you can double-quote the column name. For example,
<literal>VALUE</> is a keyword, so this does not work:
<programlisting>
SELECT a value, b + c AS sum FROM ...
</programlisting>
but this does:
<programlisting>
SELECT a "value", b + c AS sum FROM ...
</programlisting>
For protection against possible
future keyword additions, it is recommended that you always either
write <literal>AS</literal> or double-quote the output column name.
</para>
<note>
<para>
The naming of output columns here is different from that done in