$sql = "INSERT INTO  . DB_PREFIX . product_special (product_special_id, product_id, customer_group_id, priority, price, date_start, date_end ) VALUES (Null, '(int)$product_id' , '8' , '1','(float)$data['price']' , '$data['kampanyabaslangic']' , '$data['kampanyabitis']')";

$this->db->query($sql);

$prefix=DB_PREFIX;
$price=$data["price"];
$date_start=$data["kampanyabaslangic"];
$date_end=$data["kampanyabitis"];
$sql="INSERT INTO $prefixproduct_special SET 
product_special_id=Null,
product_id='$product_id',
customer_group_id='8',
priority='1',
price='$price',
date_start='$date_start',
date_end='$date_end'";
$this->db->query($sql);