title: How do I increment a value with mysql update query (php)
body: <p>I have a query that looks like this:</p>
  
  <pre><code>$sql = "UPDATE tbl SET amt_field='amt_field+1' WHERE username='" .mysql_real_escape_string($_SESSION['username']). "'";
          mysql_select_db('db',$con);
          mysql_query($sql,$con);
  </code></pre>
  
  <p>I want to increment the value as easily as possible.</p>
  
  <p>I have tried:</p>
  
  <pre><code>"UPDATE tbl SET amt_field='amt_field+1' WHERE
  
  "UPDATE tbl SET amt_field='amt_field' + 1 WHERE
  
  "UPDATE tbl SET amt_field='amt_field++' WHERE
  </code></pre>
  
  <p>I don't get error messages, but the value in my db does not increase either.</p>