$query = db_select('tablename', 't')
   ->extend('PagerDefault')
   ->limit(50)
   ->extend('TableSort')

 // ...

 $query = $query->orderByHeader($header)
 $results = $query->execute();

$header = array(
  'title' => array(
    'data' => t('Date'),
    'type' => 'field',
    'specifier' => array(
      'field' => 'field_articledate',
      'column' => 'value',
    ),
  ),
);
$query = new EntityFieldQuery();
$query->entityCondition('entity_type', 'node')
  ->entityCondition('bundle', 'article')
  ->propertyCondition('status', 1);

$query = $query->tableSort($header);
$query = $query->pager(100);

$results = $query->execute();