my requirement is to add shipping cost in sales order grid,i added below code in _preparecolumns(),
$this->addColumn('base_shipping_amount', array( 'header' => $helper->__('Shipping Amount (Base)'), 'index' => 'base_shipping_amount' ));
and added below code in _prepareCollection()
$collection->getSelect()->join(array('p' => 'sales/order_payment'), 'main_table.entity_id = p.parent_id', array( 'payment_method' => 'method' ))
its giving me error . Any help would be appreciated.