使用codeigniter中的第二个数据库执行SQL查询

Question

I want to get the data from the second database connected to Codeigniter using a SQL query.

Sample code :

$db2 = $this->load->database('second_db', true);
$product_id = implode(",", $product_id);
$query = $db2->prepare("SELECT * FROM rt_product_details WHERE id IN ($product_id)");

if ($query->execute()) {
    $result = $query->fetchall(PDO::FETCH_ASSOC);
    var_dump($result);die;
}