Answered by : officiallym

function hook_node_update($node) { db_update('mytable') ->fields(array( 'extra' => $node->extra, )) ->condition('nid', $node->nid) ->execute();
}

Source : https://api.drupal.org/api/drupal/modules%21node%21node.api.php/function/hook_node_update/7.x | Last Update : Wed, 13 Apr 22