Table per Concrete Class Strategy
Table per Concrete Class Strategy
entered into the discriminator column for each entity in a class hierarchy. You may only
decorate concrete entity classes with @DiscriminatorValue.
discriminator column, the Persistence provider will provide a default, implementation-specific
value. If the discriminatorType element of @DiscriminatorColumn is
DiscriminatorType.STRING
that cover the entire entity class hierarchy. However, it requires the columns that contain the
state of subclasses to be nullable.
is mapped to a separate table in the database. All fields or properties in the class, including
inherited fields or properties, are mapped to columns in the class's table in the database.
SQL UNION queries or separate SQL queries for each subclass for queries that cover the entire
entity class hierarchy.
providers. The default Java Persistence API provider in the Application Server does not support
this strategy.
is represented by a single table, and each subclass has a separate table that only contains those
fields specific to that subclass. That is, the subclass table does not contain columns for inherited
fields or properties. The subclass table also has a column or columns that represent its primary
key, which is a foreign key to the primary key of the superclass table.
join operations to be performed when instantiating entity subclasses. This may result in poor
performance for extensive class hierarchies. Similarly, queries that cover the entire class
hierarchy require join operations between the subclass tables, resulting in decreased
performance.
require a discriminator column in the table that corresponds to the root entity when using the
joined subclass strategy. If you are not using automatic table creation in your application, make
sure the database table is set up correctly for the discriminator column defaults, or use the
@DiscriminatorColumn