如何在Doctrine 2.0中编写UNION

Question

如何在Doctrine 2.0中编写此SQL查询（并获取结果）？

(SELECT 'group' AS type, 
    CONCAT(u.firstname, " ", u.surname) as fullname, 
    g.name AS subject,
    user_id, 
    who_id, 
    group_id AS subject_id,
    created 
  FROM group_notification 
  JOIN users u ON(who_id = u.id) 
  JOIN groups g ON(group_id = g.id)
)

   UNION

(SELECT 'event' AS type, 
    CONCAT(u.firstname, " ", u.surname) as fullname, 
    e.name AS subject, 
    user_id, 
    who_id, 
    event_id AS subject_id, 
    created 
  FROM event_notification 
  JOIN users u ON(who_id = u.id) 
  JOIN events e ON(event_id = e.id)
)
   ORDER BY created

Answer 1

好吧，我发现也许是最好的解决方案：

/**
 * @Entity
 * @InheritanceType("JOINED")
 * @DiscriminatorColumn(name="discr", type="string")
 * @DiscriminatorMap({"group" = "NotificationGroup", "event" = "NotificationEvent"})
 */
class Notification {
   // ...
}

然后是两个类（ NotificationGroup 和 NotificationEvent ），它们扩展了 Notification ：

/**
 * @Entity
 */
class NotificationGroup extends Notification {
    //...
}

/**
 * @Entity
 */
class NotificationEvent extends Notification {
    //...
}