public function getOrderByExpr($clause = null)
 {
     if (!$this->getGroupByParameter()) {
         return parent::getOrderByExpr($clause);
     }
     return 'GROUP BY ' . $this->getGroupByParameter();
 }
 /**
  * Prepare the list data configuration.
  *
  * @return SQLListDataConfig
  */
 protected function prepareListDataConfig()
 {
     $user = BackendUser::getInstance();
     $config = new SQLListDataConfig();
     $config->setTable('tl_calendar');
     $config->setKeyColumn('id');
     $config->addColumns($this->getColumns());
     // Todo is search column must be configured
     $config->addSearchColumns('title');
     $config->setOrderByExpr('title');
     $config->setLabelCallback($this->prepareLabelCallback($config));
     $config->setIconCallback($this->prepareIconCallback());
     if (!$user->isAdmin && count($user->calendars) > 0) {
         $config->setConditionExpr('id IN (' . implode(', ', $user->calendars) . ')');
     }
     return $config;
 }
 /**
  * Get list data config.
  *
  * @param $pid
  *
  * @return SQLListDataConfig
  */
 protected function getListDataConfig($pid = null)
 {
     $config = new SQLListDataConfig();
     $config->setTable('tl_article');
     $config->setKeyColumn('id');
     $config->setOrderByExpr('sorting');
     $config->setColumns($this->getColumns());
     // Todo is search column must be configured
     $config->addSearchColumns('title');
     $config->setLabelCallback($this->getLabelCallback($config));
     $config->setIconCallback($this->getIconCallback());
     $config->setContentCallback($this->getContentCallback());
     if ($pid) {
         $config->setConditionExpr('pid=' . $pid);
     }
     return $config;
 }