$resultSetMappingBuilder = new ResultSetMappingBuilder($this->entityManager);
        $resultSetMappingBuilder->addRootEntityFromClassMetadata('BeckyEntityAccount', 'a');

        $sqlQuery = 'SELECT a.* FROM `account` a
            INNER JOIN `user` u
            ON `u`.`account_id` = `a`.`id`
            WHERE `u`.`type` = 'trial'
            ORDER BY `u`.`modified_on` ASC;';
        $query = $this->entityManager->createNativeQuery($sqlQuery, $resultSetMappingBuilder);

class Account extends Entity
{
   ....
     /**
     * @ORMOneToMany(targetEntity="ProjectEntityUser", cascade={"all"}, mappedBy="account")
     */
    protected $users;
   ...
}

/**
 * @ORMEntity
 * @ORMTable(name="user", options={"collate"="utf8_general_ci"})
 * @ORMInheritanceType("SINGLE_TABLE")
 * @ORMDiscriminatorColumn(name="type", type="string")
 * @ORMDiscriminatorMap({
 *     "trial"      = "ProjectEntityUserTrial",
 *     "admin"      = "ProjectEntityUserAdmin",
 *     "sales"      = "ProjectEntityUserSales"
 * })
 */
abstract class User extends Entity
{
...
    /**
     * @ORMManyToOne(targetEntity="ProjectEntityAccount", inversedBy="users")
     * @ORMJoinColumn(name="account_id", referencedColumnName="id")
     * @var Account
     */
    protected $account;
}