 data for the entity class is stored across multiple tables.

 <p> If no <code>SecondaryTable</code> 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.

 <pre>
    Example 1: Single secondary tabl