Re: alias required by standard or PostgreSQL?

"Joost Kraaijeveld" <J(dot)Kraaijeveld(at)Askesis(dot)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