Drupal 7: revert language column to "und" on locale uninstallation, this is not for site with multilanguage, only for site with unused/unconfigured locale

revert_locale_lang.php

<?php

// Use this to identify possible table needs to be updated
//   SELECT DISTINCT TABLE_NAME 
//   FROM INFORMATION_SCHEMA.COLUMNS
//   WHERE COLUMN_NAME IN ('language')
//   AND TABLE_SCHEMA='<YOUR_DATABASE>';

// include other custom fields
$tables = array(
  'node',
  'url_alias',
  'field_data_body',
  'field_data_comment_body',
  'field_revision_body',
  'field_revision_comment_body',
);

foreach ($tables as $table) {
  db_update($table)
    ->fields(array(
      'language' => 'und',
    ))
    ->execute();
}