Magento2 custom sql to get data from external table and import into product

Question

In Magento2 I am trying to connect to an external database and table and use the data to update a custom product attribute where the sku' match in both tables. I temporarily put this code in my footer.phtml file as I am just trying. ti do a quick import/population of custom attributes from an external source

I am trying to do the below query. If I remove my query code and just card code a sku and a part id it updates Magento just fine so something about my sql it does not like. I confirmed my credentials are valid for accessing the database

$machine = "xxxxx";
$machineu = "xxxx";
$machinep = "xxx";
$machinedbname = "xxxx";

// Create connection
$conn = mysqli_connect($machine, $machineu, $machinep, $machinedbname);
if (!$conn) {
   die("Connection failed: " . mysqli_connect_error());
}

$testsql = mysqli_query($conn, "SELECT * FROM tempinfo");
while($row = mysqli_fetch_array($testsql))
{
  extract($row);
  echo "<p style='color:#ffffff'>test $sku</p><br />";
  $_product = $objectManager->create('\Magento\Catalog\Api\ProductRepositoryInterface')->get($sku,true, 0, true);
  $_product->setCustomAttribute("part_id", "$part_id");
  $_product->save($_product);
}

Answer 1

I am also using an external database to update some product infos, but I use PDO.

Maybe this helps:

     $sku=$_product->getSku();
     try {
             $conn = new \PDO("mysql:host=$servername;dbname=$dbname;port=$port", $username, $password);

             $selection="SELECT * from table WHERE id='$sku';
             foreach ($conn->query($selection) as $dbitem) {
               $_product->setCustomAttribute("part_id", $dbitem['part_id']);
               $_product->save();
             }
      } catch(PDOException $e) {
        echo "Connection failed: " . $e->getMessage();
      }