gistfile1.php

<?php
protected function _prepareCollection()
    {
        $filters = $this->getRequest()->getParams();
        $start_date = (isset($filters['date_from'])) ? date("'Y-m-d'", strtotime($filters['date_from'])) : "'0000-00-00'";
        $end_date   = (isset($filters['date_to'])) ? date("'Y-m-d'", strtotime($filters['date_to'])) : 'NOW()';

        $collection = Mage::getModel("sales/order")->getCollection();
        $resource = Mage::getSingleton('core/resource');
        $distributorTable     = $resource->getTableName('PurinaPro_Groups/Distributor');
        $distributorLinkTable = $resource->getTableName('PurinaPro_Groups/Distributor_OrderLink');

        $months = $this->getMonths();

        $collection->getSelect()
            ->reset(Zend_Db_Select::COLUMNS)
            ->join(array("distributor_link"=>$distributorLinkTable),"main_table.entity_id = distributor_link.order_id",array())
            ->join(array("distributor"=>$distributorTable),"distributor_link.distributor_id = distributor.id",array())
            ->columns(array(
                "customer_id" => "main_table.customer_id",
                "firstname"=>"main_table.customer_firstname",
                "lastname"=>"main_table.customer_lastname",
                "distributor_name"=>"distributor.name",
                "order_months_count" => "(select COUNT(distinct MONTH(created_at)) from sales_flat_order where customer_id=main_table.customer_id and created_at between $start_date and $end_date)",
                "total_qty_ordered" => "(select sum(total_qty_ordered) from sales_flat_order where customer_id=main_table.customer_id and created_at between $start_date and $end_date)",
                "total_grand_total" => "(select sum(base_grand_total) from sales_flat_order where customer_id=main_table.customer_id and created_at between $start_date and $end_date)",
            ));

        foreach($months as $key => $month){

            $collection->getSelect()
                ->columns(array(
                    $month."_count" => "sum(MONTH(main_table.created_at) = $key)",
                    $month."_total" => "(select sum(base_subtotal) from sales_flat_order where month(created_at) = $key and customer_id=main_table.customer_id and created_at between $start_date and $end_date)",
                    #$month."_grand_total" => "(select sum(base_grand_total) from sales_flat_order where month(created_at) = $key and customer_id=sfo.customer_id and created_at between $start_date and $end_date)",
                ));
        }

        $collection->getSelect()
            ->where('main_table.customer_id IS NOT NULL')
            ->where("main_table.created_at between $start_date and $end_date")
            ->group('main_table.customer_id');


        $this->setCollection($collection);

        $this->addExportType('*/*/exportCsv', Mage::helper('reports')->__('CSV'));

        return parent::_prepareCollection();
    }