union-query all tables of a pgsql 7.0.3.-db (on solaris)

hi there!
i´m absolute new with postgresql so i maybe ask very simle things - sorry for that ;) :

i have two databases, one with headdata and one with detaildata (i´m not the creator and i cant change that).

now i have to join the detaildata with the corresponding headdata across the databases.

my idea is to dump all detaildata-tables in one big table (the structure of the tables is identical so that a union-query should work fine) and import them in the headdata-database.

how can i do that in a efficient way? or is there a better possibility to join the databases?

thx4hlp
peter