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To: "Joost Kraaijeveld" <J.Kraaijeveld@Askesis.nl>
cc: pgsql-sql@postgresql.org
Subject: Re: alias required by standard or PostgreSQL? 
In-reply-to: <1196661149.5542.33.camel@panoramix.askesis.nl> 
References: <1196661149.5542.33.camel@panoramix.askesis.nl>
Comments: In-reply-to "Joost Kraaijeveld" <J.Kraaijeveld@Askesis.nl>
	message dated "Mon, 03 Dec 2007 06:52:29 +0100"
Date: Mon, 03 Dec 2007 01:13:29 -0500
Message-ID: <9788.1196662409@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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"Joost Kraaijeveld" <J.Kraaijeveld@Askesis.nl> writes:
> "select * from (select * from table_name)" 

> PostgreSQL complains with 

> ERROR:  subquery in FROM must have an alias
> HINT:  For example, FROM (SELECT ...) [AS] foo.

> Is the alias required by the ISO standard

Yes.  A FROM-clause entry is defined as

         <table reference> ::=
                <table name> [ [ AS ] <correlation name>
                    [ <left paren> <derived column list> <right paren> ] ]
              | <derived table> [ AS ] <correlation name>
                    [ <left paren> <derived column list> <right paren> ]
              | <joined table>

         <derived table> ::= <table subquery>

Note that the brackets show that a <correlation name> (ie, an alias)
is optional for a regular table, but not for a subquery.

			regards, tom lane