/** * Returns expression for field unification * * @param string $field * @param string $backendType * @return \Zend_Db_Expr */ private function unifyField($field, $backendType = 'varchar') { if ($backendType == 'datetime') { $expr = $this->connection->getDateFormatSql($field, '%Y-%m-%d %H:%i:%s'); } else { $expr = $field; } return $expr; }