This example shows how to use persistent class inheritance. The example consists of the following files: employee.hxx Header file defining the 'person' and 'employee' abstract persistent classes as well as the 'permanent_employee', 'temporary_employee', and 'contractor' concrete persistent classes. employee-odb.hxx employee-odb.ixx employee-odb.cxx employee.sql The first three files contain the database support code and the last file contains the database schema for the employee.hxx header. These files are generated by the ODB compiler from employee.hxx using the following command line: odb -d <database> --generate-schema --generate-query employee.hxx Where <database> stands for the database system we are using, for example, 'mysql'. database.hxx Contains the create_database() function which instantiates the concrete database class corresponding to the database system we are using. driver.cxx Driver for the example. It includes the employee.hxx and employee-odb.hxx headers to gain access to the persistent classes and their database support code. It also includes database.hxx for the create_database() function declaration. In main() the driver first calls create_database() to obtain the database instance. It then persists a number of permanent and temporary employee objects as well as a number of contractor objects. The next transaction looks up a contractor based on the email address. Finally, the driver performs a database query which uses a data member from the base class in its criterion. To run the example we may first need to create the database schema (for some database systems, such as SQLite, the schema is embedded into the generated code which makes this step unnecessary). Using MySQL as an example, this can be achieved with the following command: mysql --user=odb_test --database=odb_test < employee.sql Here we use 'odb_test' as the database login and also 'odb_test' as the database name. Once the database schema is ready, we can run the example (using MySQL as the database): ./driver --user odb_test --database odb_test