title: MySQL trigger before insert update column with new auto-increment id
body: <p>I'd like to update a column in my table with the country code and the new <code>id</code> which is an auto-increment value.</p>
  
  <pre><code>BEGIN
  SET new.key = concat(new.countryCode,new.id);
  END
  </code></pre>
  
  <p><code>countryCode</code> works fine, but the <code>id</code> is always blank. How can I achieve something like this? The <code>id</code> comes from an <code>autoincrement</code> column.</p>
  
  <p>I know it's not working because it's generated after the insert. So how can I do something like this?</p>