Hibernate version:
3.2.5g

I have an application that use spring to initiate two data sources, one external DB and one embedded DB (Derby) and mapping files external.hbm.xml and embedded.hbm.xml. (Since I'm using spring, I don't have a hibernate.cfg.xml file) For my development, hbm2ddl=create-drop works great for this setup. For production though, the DB should be created only once and data should be retained. To my surprise, hbm2ddl=create will also drop the table content as well. So I am thinking to generate schema using an ant script, which would be executed on external DB before the application starts. The embedded DB on the other hand, it should not require any user setup so I don't think generating schema would be a good idea. So I am wondering if there is any other tools or settings I could use to generate/create table for just once and still retain the data?

Regards,

AFAIK not using Hibernate.
You're probably going to have to write something yourself that checks whether the tables exist and creates them if not (of course you'll also have to check whether the database exists...).

Try with hbm2ddl=update
This will update the schema as best as possible to match the mapping files. I say "as best as possible" because certain changes can't be applied. Consider adding a not-null to a column in the mapping file when nulls apready exist in the database data.