Schema API - Create table field.php

<?php
// $Id$

/**
 * @see Schema API documentation: http://api.drupal.org/api/group/schemaapi/6
 * @see http://api.drupal.org/api/function/drupal_get_schema/6
 * @see http://api.drupal.org/api/function/db_add_field/6
 */

/**
 * Implements hook_update_N().
 */
function w_update_1() {
  $ret = array();
  $table_schema = drupal_get_schema('site_inventory', TRUE);
  db_add_field($ret, 'site_inventory', 'received_date',   $table_schema['fields']['received_date']);

  return $ret;
}
?>