XREL keyword
The XREL keyword is used to build relationships independent of how the data was retrieved. XREL is valid only in Enterprise JavaBeans (EJB) Mediator queries.
XREL does not retrieve additional data, it only builds relationships
from data already retrieved by the select statements. The relationships
can be one-to-one, one-to-many, many-to-one, or many-to-many. The
relationships can be unidirectional or bidirectional. If you specify
a bidirectional relationship in an XREL, the inverse relationship
is also established in addition to the specified relationship.
xrel := XREL identification_variable . { single_valued_cmr_field | collection_valued_cmr_field } [ , identification_variable . { single_valued_cmr_field | collection_valued_cmr_field } ]*
Examples: XREL keyword
This example retrieves
all employees and all departments, and establishes the emps and mgr relationships.
select e.name from EmpBean e select d.name from DeptBean d xrel d.emps, d.mgrNotice that the employees are retrieved through d.emps relationship, xrel d.mgr is to establish the mgr relationship for those employees who are also a manager.
select d.name from DeptBean d select e.name from in(d.emps) e xrel d.mgr