Chapter 11. Schema Management
One of Hibernate's most useful features is the automatic generation of schema manipulation commands. This feature, sometimes referred to as the ability to generate Data Definition Language (DDL) scripts, makes it possible (given a valid *.hbm.xml file) to create, update, and even drop tables in a target database. You can do this at runtime, during development, or via scripts generated for later use by a system administratoran invaluable capability if you expect to support multiple target databases (during either development or deployment) or have a high degree of database schema change.
Hibernate supports two basic forms of DDL generation, update and export. Update is generally used within an application, targeting a specific database that may already contain a portion of the schema (and hence application data) but is missing schema components required by a new application. Export is used to generate the schema from scratch; it is especially useful if the application is not allowed to directly execute DDL (because, say, a database administrator is expected to perform these tasks).
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