Zend_-DB查询和行数,而不将所有内容都拉回到前面

我已经创建了我的选择:

$select = $zdb->select()
              ->from(array("b" => "blogs"),
                     array("id", "active", "updated_by", "title", "synopsis", "create_date", "body"))
              ->join(array("u" => "users"),
                     'b.updated_by = u.id',
                     array("first_name", "last_name"))
              ->where("u.blogger = ?", 1)
              ->where("b.publish_date > ?", '2020-01-01')
              ->where("b.active = ?", 1)
              ->group("b.id")
              ->order("b.publish_date DESC")
              ->limit(5);

我想一次把数据拉回一行:

$stmt = $db->query($select);

while ($asset = $stmt->fetch()) {
    // do stuff
}

如何检查以确保有行,而不返回整个结果集?