@Repeatable(value=PrimaryKeyJoinColumns.class) @Target(value={TYPE,METHOD,FIELD}) @Retention(value=RUNTIME) public @interface PrimaryKeyJoinColumn
 It is used to join the primary table of an entity subclass 
 in the JOINED mapping strategy 
 to the primary table of its superclass; it is used within a 
 SecondaryTable annotation to join a secondary table 
 to a primary table; and it may be used in a OneToOne 
 mapping in which the primary key of the referencing entity 
 is used as a foreign key to the referenced entity. 
 
 If no PrimaryKeyJoinColumn annotation is 
 specified for a subclass in the JOINED
 mapping strategy, the foreign key columns are assumed 
 to have the same names as the primary key columns of the 
 primary table of the superclass.
 
    Example: Customer and ValuedCustomer subclass
    @Entity
    @Table(name="CUST")
    @Inheritance(strategy=JOINED)
    @DiscriminatorValue("CUST")
    public class Customer { ... }
    
    @Entity
    @Table(name="VCUST")
    @DiscriminatorValue("VCUST")
    @PrimaryKeyJoinColumn(name="CUST_ID")
    public class ValuedCustomer extends Customer { ... }
 SecondaryTable, 
Inheritance, 
OneToOne, 
ForeignKey| Modifier and Type | Optional Element and Description | 
|---|---|
| String | columnDefinition(Optional) The SQL fragment that is used when generating the 
 DDL for the column. | 
| ForeignKey | foreignKey(Optional) Used to specify or control the generation of a
  foreign key constraint for the primary key join column 
  when table generation is in effect. | 
| String | name(Optional) The name of the primary key column of the current table. | 
| String | referencedColumnName(Optional) The name of the primary key column of the table
 being joined to. | 
public abstract String name
 Defaults to the same name as the primary key column 
 of the primary table of the superclass (JOINED mapping strategy); the same 
 name as the primary key column of the primary table 
 (SecondaryTable mapping); or the same name as the 
 primary key column for the table for the referencing entity 
 (OneToOne mapping).
public abstract String referencedColumnName
 Defaults to the same name as the primary
 key column of the primary table of the superclass
 (JOINED mapping strategy); the same name as the
 primary key column of the primary table
 (SecondaryTable mapping); or the same name as the
 primary key column for the table for the referencing entity
 (OneToOne mapping).
public abstract String columnDefinition
OneToOne primary key association.
 Defaults to the generated SQL to create a column of the inferred type.
public abstract ForeignKey foreignKey
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