Format using MYSQL Date Retrieved from Database and Display in PHP file

I am retrieving a date from my database. Now my assignment calls to format it using MYSQL. I've tried using a similar call as I did to retrieve the data, but I keep getting the error message "Call to a member function fetch_object() on a non-object".

//RETRIEVE DATA FROM DATABASE INCLUDING $blog_date

  $db = new mysqli($host,$user,$pw,$database)
        or die("Cannot connect to MySQL.");

  $command = "select * from ".$table_name." where blog_id=".$blogId;
  $result = $db->query($command);
  while ($data = $result->fetch_object()) 
  {
    $blog_title = $data->blog_title;
    $blog_author = $data->blog_author;
    $blog_date = $data->date_of_blog;
    $blog_entry = $data->blog_entry;
  }

//Using MYSQL, I try to format $blog_date using the mysql date_format; however, I keep getting the error message "Call to a member function fetch_object() on a non-object"

  $command = "select date_format($blog_date, '%W, %m/%d/%Y') as formatted_date;";
  $result = $db->query($command); 
  while ($data = $result->fetch_object())
  {
    $blog_date_formatted = $data->formatted_date;
  }

  $db->close();

I appreciate your help!!!

Olive