public function add(EntityAdded $event)
    {
        $entity = $event->getEntity();
        $table = $this->getParentTableName();
        $pmk = $this->getParentPrimaryKey();
        $value = $event->getCollection()->parentEntity()->getId();
        Sql::createSql($this->getAdapter())
            ->update($table)
            ->set([$this->getForeignKey() => $value])
            ->where(["{$pmk} = :id" => [':id' => $entity->getId()]])
            ->execute();
    }