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This example shows how to generate and use a database schema that is embedded
into the application rather than stored as a separate SQL file.
The example consists of the following files:
person.hxx
Header file defining the 'person' persistent class.
person-odb.hxx
person-odb.ixx
person-odb.cxx
These files contain the database support code as well as the embedded
database schema for the person.hxx header. They are generated by the ODB
compiler from person.hxx using the following command line:
odb -d <database> --generate-schema --schema-format embedded \
--generate-query person.hxx
Where <database> stands for the database system we are using, for example,
'mysql'.
The --generate-schema option requests the generation of the database schema.
The --schema-format option is used to instruct the ODB compiler to embed the
schema into the generated C++ files. It is also possible to generate the
schema creation code into a separate source file by passing the 'separate'
value instead of 'embedded' to the --schema-format option. This is primarily
useful if you want to place the schema creation functionality into a
separate program or library.
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 person.hxx and person-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 uses the ODB schema catalog to create the database
schema. During this step the generated code issues a number of SQL
statements that drop and create necessary database tables, etc.
After the database schema is ready, the driver persists a number of 'person'
objects, performs a database query, and prints the information about the
returned objects.
To compile and link the example manually from the command line we can use
the following commands (using MySQL as an example; replace 'c++' with your
C++ compiler name):
c++ -c person-odb.cxx
c++ -DDATABASE_MYSQL -c driver.cxx
c++ -o driver driver.o person-odb.o -lodb-mysql -lodb
To run the driver, using MySQL as an example, we can execute the following
command:
./driver --user odb_test --database odb_test
Here we use 'odb_test' as the database login and also 'odb_test' as the
database name.
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