Hi, you know if is it possible to make a query referencing multiple DB in HQL? That is: I have three legacy system, each one with its DB (one oracle, one sqlserver, one mysql ...don't tell...), I already have all them in one application using different hibernate configuration files.
I want to make a query like

select table_from_db_a
from Table_from_db_a table_from_db_a
where table_from_db_a.commonKey not in
(select table_from_db_b.comonKey
from Table_from_db_b table_from_db_B
)

Is it possible?
Thank you,
Marco

Hi,

I'm facing a similar scenario, just with two different PostgreSQL databases. In PostgreSQL there's a feature called dblink that lets you do remote queries. I know that Oracle has got a similar feature, not sure about the others. AFAIK Hibernate hasn't got any built-in support for multiple DBs. Try mapping classes with custom SQL queries using <sql-query>, <subselect>.
Another approach would be to query all databases separately and join manually in your application code. I think there's no good solution to this.

If anyone has got a different solution I'd like to know, since my current solution is not very efficient.