Running queries from different databases and joining them

Hi,

Does anyone know if the feature to do same queries on different databases
and then join them (just like the union in SQL) exists in Postgres ?

I know that one way of doing this is to use JDBC, do different queries and
join them manually.  This is problematic for ordering and grouping since it
needs to be done manually for each query.  Is there any other elegant way
of doing this ?


Regards
Robert