title: MySQL no affected rows upon UPDATE when value not changed
body: <p>MySQL with PHP, trying to update a row:  </p>
  
  <pre><code>$dbQuery = 'UPDATE UserTable SET Age=25 WHERE Id=3';
  $result = mysqli_query($dbLink, $dbQuery);
  if ($result === FALSE) {
    // Take care of error
  }
  else {
    $numAffectedRows = mysqli_affected_rows($dbLink);
  }
  </code></pre>
  
  <p>I get zero $numAffectedRows in two <strong>different</strong> cases:<br>
   1. When there is no user row with Id=3<br>
   2. When there is a user row with Id=3 but Age was already 25 before  </p>
  
  <p>Is there a way I can <strong>distinguish</strong> between the two cases? (apart from reading the row before and manually check the value before updating)</p>