Re: SQL subquery to supply table name?

On Thu, 26 Sep 2002, Scott Chapman wrote:

> I was lead to believe that Postgresql would handle this from reading the docs.
> This error message from psql made me think it would also:
>
> select txtcompanyname from (select table_quest from reviews where
> review_num=28) where review_num=28;
>
> ERROR: sub-SELECT in FROM must have an alias
> For example, FROM (SELECT ...) [AS] foo
>
> What is the "sub-SELECT in FROM" supposed to be used for if not this usage?

It's effectively as if you defined a view with that as the definition and
used it. It mostly exists to allow multiple levels of processing (for
example, you want to do a query that does something to a set of grouped
data).