hi Ligia,
there was a posting to this list some time ago, about the same question.
I just found it as I had the same question as you:
http://archives.postgresql.org/pgsql-sql/1998-05/msg00091.php
(in short: it is not possible in Postgres)
the mail is from 1998, but I just tried to make a select using
mydatabase.mytable as table name in a select statement and this does not
work.
Chantal