If no SecondaryTable annotation is specified, it is assumed that all persistent fields or properties of the entity are mapped to the primary table. If no primary key join columns are specified, the join columns are assumed to reference the primary key columns of the primary table, and have the same names and types as the referenced primary key columns of the primary table.

Example 1: Single secondary table with a single primary key column.

    @Entity
    @Table(name="CUSTOMER")
    @SecondaryTable(name="CUST_DETAIL", 
        pkJoinColumns=@PrimaryKeyJoinColumn(name="CUST_ID"))
    public class Customer { ... }

Example 2: Single secondary table with multiple primary key columns.

    @Entity
    @Table(name="CUSTOMER")
    @SecondaryTable(name="CUST_DETAIL",
        pkJoinColumns={
            @PrimaryKeyJoinColumn(name="CUST_ID"),
            @PrimaryKeyJoinColumn(name="CUST_TYPE")})
    public class Customer { ... }