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.mgr
Notice 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  



Related concepts
EJB query language
Related tasks
Using EJB query
Using the dynamic query service
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Last updated: Oct 21, 2010 5:30:17 AM CDT
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