a:5:{i:0;s:62:"You cannot define a correlation name 'shipping' more than once";i:1;s:2687:"#0 /var/www/vhosts/MYSITE/httpdocs/lib/Varien/Db/Select.php(281): Zend_Db_Select->_join('left join', Array, 'main_table.enti...', Array, NULL)
#1 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Zend/Db/Select.php(373): Varien_Db_Select->_join('left join', Array, 'main_table.enti...', Array, NULL)
#2 /var/www/vhosts/MYSITE/httpdocs/app/code/local/Atwix/ExtendedGrid/Model/Observer.php(34): Zend_Db_Select->joinLeft(Array, 'main_table.enti...', Array)
#3 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Core/Model/App.php(1357): Atwix_ExtendedGrid_Model_Observer->salesOrderGridCollectionLoadBefore(Object(Varien_Event_Observer))
#4 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Core/Model/App.php(1336): Mage_Core_Model_App->_callObserverMethod(Object(Atwix_ExtendedGrid_Model_Observer), 'salesOrderGridC...', Object(Varien_Event_Observer))
#5 /var/www/vhosts/MYSITE/httpdocs/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('sales_order_gri...', Array)
#6 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Core/Model/Resource/Db/Collection/Abstract.php(590): Mage::dispatchEvent('sales_order_gri...', Array)
#7 /var/www/vhosts/MYSITE/httpdocs/lib/Varien/Data/Collection/Db.php(565): Mage_Core_Model_Resource_Db_Collection_Abstract->_beforeLoad()
#8 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php(951): Varien_Data_Collection_Db->load()
#9 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php(1008): Mage_Adminhtml_Block_Widget_Grid->_exportIterateCollection('_exportCsvItem', Array)
#10 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Adminhtml/controllers/Sales/OrderController.php(703): Mage_Adminhtml_Block_Widget_Grid->getCsvFile()
#11 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Adminhtml_Sales_OrderController->exportCsvAction()
#12 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('exportCsv')
#13 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#14 /var/www/vhosts/MYSITE/httpdocs/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#15 /var/www/vhosts/MYSITE/httpdocs/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#16 /var/www/vhosts/MYSITE/httpdocs/index.php(87): Mage::run('', 'store')
#17 {main}";s:3:"url";s:103:"/index.php/spadmin/sales_order/exportCsv/key/54346fe7eb59bee82fd6e0a6aa777ff2/internal_order_ids/21318/";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:5:"admin";}

<?xml version="1.0"?>
<config>
    <modules>
        <Atwix_ExtendedGrid>
            <version>1.0.1</version>
        </Atwix_ExtendedGrid>
    </modules>
    <global>
        <blocks>
            <atwix_extendedgrid>
                <class>Atwix_ExtendedGrid_Block</class>
            </atwix_extendedgrid>
        </blocks>
        <helpers>
            <atwix_extendedgrid>
                <class>Atwix_ExtendedGrid_Helper</class>
            </atwix_extendedgrid>
        </helpers>
        <models>
            <atwix_extendedgrid>
                <class>Atwix_ExtendedGrid_Model</class>
            </atwix_extendedgrid>
            <sales_resource>
                <rewrite>
                    <order_grid_collection>Atwix_ExtendedGrid_Model_Resource_Sales_Order_Grid_Collection</order_grid_collection>
                </rewrite>
            </sales_resource>
        </models>
    </global>
    <adminhtml>
        <events>
            <sales_order_grid_collection_load_before>
                <observers>
                    <atwix_exgrid>
                        <model>atwix_extendedgrid/observer</model>
                        <method>salesOrderGridCollectionLoadBefore</method>
                    </atwix_exgrid>
                </observers>
            </sales_order_grid_collection_load_before>
        </events>
        <layout>
            <updates>
                <atwix_extendedgrid>
                    <file>atwix/extendedgrid.xml</file>
                </atwix_extendedgrid>
            </updates>
        </layout>
    </adminhtml>
</config>

<?php

class Atwix_ExtendedGrid_Model_Observer
{
    /**
     * Joins extra tables for adding custom columns to Mage_Adminhtml_Block_Sales_Order_Grid
     * @param Varien_Object $observer
     * @return Atwix_Exgrid_Model_Observer
     */
    public function salesOrderGridCollectionLoadBefore($observer)
    {
        $collection = $observer->getOrderGridCollection();
        $select = $collection->getSelect();
        $collection->getSelect()->joinLeft(array('shipping'=>'sales_flat_order_address'),
    'main_table.entity_id = shipping.parent_id AND shipping.address_type="shipping"',array('shipping.country_id AS bp'));
        $select->group('main_table.entity_id');
    }

    /**
     * callback function used to filter collection
     * @param $collection
     * @param $column
     * @return $this
     */

}

<?php

class Atwix_ExtendedGrid_Model_Resource_Sales_Order_Grid_Collection extends Mage_Sales_Model_Resource_Order_Grid_Collection
{

    /**
     * Get SQL for get record count
     *
     * @return Varien_Db_Select
     */
    public function getSelectCountSql()
    {
        $countSelect = parent::getSelectCountSql();

        if (Mage::app()->getRequest()->getControllerName() == 'sales_order') {
            $countSelect->reset(Zend_Db_Select::GROUP);
            $countSelect->reset(Zend_Db_Select::COLUMNS);
            $countSelect->columns("COUNT(DISTINCT main_table.entity_id)");

            $havingCondition = $countSelect->getPart(Zend_Db_Select::HAVING);
            if (count($havingCondition)) {
                $countSelect->where(
                    str_replace("group_concat(`sales_flat_order_item`.sku SEPARATOR ', ')", 'sales_flat_order_item.sku', $havingCondition[0])
                );
                $countSelect->reset(Zend_Db_Select::HAVING);
            }
        }

        return $countSelect;
    }

    /**
     * Init select
     * @return Mage_Core_Model_Resource_Db_Collection_Abstract
     */
    protected function _initSelect()
    {
        $this->addFilterToMap('store_id', 'main_table.store_id')
            ->addFilterToMap('created_at', 'main_table.created_at')
            ->addFilterToMap('updated_at', 'main_table.updated_at');
        return parent::_initSelect();
    }
}

<?php


class Atwix_ExtendedGrid_Helper_Data extends Mage_Core_Helper_Abstract
{
    /**
     * parameters for addColumnAfter method
     * @return array
     */
    public function getSkusColumnParams()
    {
        return array(
        'header' => Mage::helper('sales')->__('Shipping Country'),
        'index' => 'bp',
        'width' => '60px',
        'filter_index'  => 'shipping.country_id'
    );
    }
}

#1 /var/www/html/lib/Zend/Db/Select.php(357): Varien_Db_Select->_join('left join', Array, 'payment.parent_...', Array, NULL)
#2 /var/www/html/app/code/local/Atwix/ExtendedGrid/Model/Observer.php(33): Zend_Db_Select->joinLeft(Array, 'payment.parent_...', Array)