The Java EE 6 Tutorial, Volume I


A path expression enables the query to navigate to related entities. The terminating elements of an expression determine whether navigation is allowed. If an expression contains a single-valued relationship field, the navigation can continue to an object that is related to the field. However, an expression cannot navigate beyond a persistent field or a collection-valued relationship field. For example, the expression is illegal, because teams is a collection-valued relationship field. To reach the sport field, the FROM clause could define an identification variable named t for the teams field:

FROM Player AS p, IN (p.teams) t
 WHERE = ’soccer’