I get the following error message while updating a Drupal site I keep getting this error when I try to update Drupal. I have no clue what it means; it seems I have a missing column.


  PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'base.access_exposed' in 'field list':
  SELECT base.id AS id, base.name AS name, base.label AS label, base.plugin AS plugin, base.active AS active, base.weight AS weight, base.status AS status, base.dirty AS dirty, base.module AS module, base.access_exposed AS access_exposed, base.data AS data FROM {rules_config} base WHERE (base.status IN (:db_condition_placeholder_0, :db_condition_placeholder_1, :db_condition_placeholder_2)) ; Array ( [:db_condition_placeholder_0] => 3 [:db_condition_placeholder_1] => 2 [:db_condition_placeholder_2] => 6 ) in EntityAPIController->query() (line 152 of /opt/readyby21.org/public_html/sites/all/modules/contrib/entity/includes/entity.controller.inc).
According to http://drupal.org/node/1489394 some users experienced this problem when updating their rules module.  It looks like you'll need to update your rules, entity and internationalization modules all need to be updated to the latest versions (7.x-1.5 for internationalization and 7.x-1.0-rc2 for entities).  If you already have, try only updating those modules, before attempting to update the rules module (you can disable the rules module.  This should also solve the problem, but I assume you're using it for something or other).

As BetaRide points out above, checking into your web logs may shed some additional light on the problem, in case the above doesn't solve the problem.