Merging databases

Hello everybody

I am very new at datamangement and I want to merge the data of two (or
more) databases.

My current "solution" and my problem:
- First the primary ids of the tables are unique over all the databases
(different offsets for each db). And I don't want to delete any records
(they just be marked as deleted), so I just want to get the combination
of the two databases.
- Then I COPY each table of the 1st db in a corresponding file.
- In the 2nd db I create an empty, comatible, temporary table (CREATE
TABLE tmptable AS SELECT * FROM table; DELETE FROM tmptable;) Does
somebody have a better,faster idea?
- Then I COPY the corresponding file into the temprary table.
- And I reached my problem step: How to get only the additional records
from the temporary table in the tableX??? Some of the tables have
compound primary keys.
- DROP the tmptable.
- The same thing for the other db.

Does somebody have a solution for my problem or even a better, faster
solution to merge
two databases.

I am using PostgreSQL 6.3.2 (soon 6.4) with the JDBC interface.

Thanks in advance for every replay!
Bruno

--
 _  _ ___ ___  Bruno Feurer
| || / __| _ \ HSR Hochschule Rapperswil; Oberseestrasse 10;
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|_||_|___/_|_\ EMAIL: bfeurer@hsr.ch; WWW:www.hsr.ch