title: MySQL & PHP - Not unique table/alias
body: <p>I get the following error listed below and was wondering how do I fix this problem.</p>
  
  <pre><code>Not unique table/alias: 'grades'
  </code></pre>
  
  <p>Here is the code I think is giving me the problem.</p>
  
  <pre><code>function getRating(){
  $dbc = mysqli_connect ("localhost", "root", "", "sitename");
  
  $page = '3';
  
  $sql1 = "SELECT COUNT(*) 
           FROM articles_grades 
           WHERE users_articles_id = '$page'";
  
  $result = mysqli_query($dbc,$sql1);
  
  if (!mysqli_query($dbc, $sql1)) {
          print mysqli_error($dbc);
          return;
  }
  
  $total_ratings = mysqli_fetch_array($result);
  
  $sql2 = "SELECT COUNT(*) 
           FROM grades 
           JOIN grades ON grades.id = articles_grades.grade_id
           WHERE articles_grades.users_articles_id = '$page'";
  
  $result = mysqli_query($dbc,$sql2);
  
  if (!mysqli_query($dbc, $sql2)) {
          print mysqli_error($dbc);
          return;
  }
  
  $total_rating_points = mysqli_fetch_array($result);
  if(!empty($total_rating_points) &amp;&amp; !empty($total_ratings)){
  // set the width of star for the star rating
  $rating = (round($total_rating_points / $total_ratings,1)) * 10; 
  echo $rating;
  } else {
      $rating = 100; 
      echo $rating;
  }
  }
  </code></pre>