I'm trying to retrieve some data from database by joining 4 tables.
One approach is that I can just write a single SQL statement to do the work.
But if I use HQL, behind the scene, Hibernate generated more than 8 SQL satements.
My question is that will this be an performance impact on my application? What benefit does Hibernate provide in terms of performance in my case?
(It's a silly question, but I still hope to find a explanation/answer...).
Thanks.

Firstly, you can control Hibernate fetch strategy, for example in the mapping you can specify fetch="join"
http://www.hibernate.org/hib_docs/v3/re ... -outerjoin

Note: in 3.0.5 fetch=”join” has no effect on retrieving object as a part of HQL select, but works properly when we ask session for the object, i.e. session.get( ObjectClass.class, id );

Secondly: getting all the objects with JOIN might actually cause performance to deteriorate. It may happen when linked tables have small number of records, in this case it is cheaper to get the objects from session or second level cache than transfer them from DB as a result of a big jojn.