I am having a complex sql query to make custom report & showing same to custom report grid but somehow not able to convert the query into Magento’s equivalent Collection.

SELECT SUM(order_items.qty_ordered) AS `ordered_qty`, `order_items`.`name` AS `order_items_name`, `order_items`.`product_id` AS `entity_id`, `e`.`entity_type_id`, `e`.`attribute_set_id`, `e`.`type_id`, `e`.`sku`, `order`.`created_at`, `order`.`updated_at`, `ps`.`qty` AS `current_stock`, (ps.qty - SUM(order_items.qty_ordered)) AS `difrnc`, `c`.`value` as `costing`, ((ps.qty - SUM(order_items.qty_ordered)) * `c`.`value`) AS `totcsttostock`           FROM `sales_flat_order_item` AS `order_items`           INNER JOIN `sales_flat_order` AS `order` ON `order`.entity_id = order_items.order_id AND `order`.state <> 'canceled'           LEFT JOIN `catalog_product_entity` AS `e` ON (e.type_id NOT IN ('grouped', 'configurable', 'bundle')) AND e.entity_id = order_items.product_id AND e.entity_type_id = 4           LEFT JOIN `cataloginventory_stock_item` AS `ps` ON ps.product_id=order_items.product_id           LEFT JOIN `catalog_product_entity_decimal` AS `c` ON c.entity_id=order_items.product_id and c.attribute_id=79           WHERE `order`.`created_at` BETWEEN '2017-09-22 00:00:00' AND '2017-09-22 23:59:59' and (parent_item_id IS NULL)           GROUP BY `order_items`.`product_id` HAVING (SUM(order_items.qty_ordered) > 0) ORDER BY `ordered_qty` desc 

I have converted this much(which might have mistakes), but needed help/suggestion ahead

function __construct() {     parent::__construct();     $  this->setResourceModel('sales/order_item');     $  this->_init('sales/order_item','item_id'); } public function setDateRange($  from, $  to) { $  this->_reset();         $  this->getSelect()              ->joinInner(array('i' => $  this->getTable('sales/order_item')),'i.order_id = main_table.entity_id','SUM(i.qty_ordered) AS ordered_qty') ->joinLeft(array('ps' => $  this->getTable('cataloginventory/stock_item')), 'ps.product_id=i.product_id', 'ps.qty as current_stock, (ps.qty - SUM(i.qty_ordered)) AS difrnc') ->joinLeft(array('e' => $  this->getTable('catalog/product')), '(e.type_id NOT IN ("grouped", "configurable", "bundle")) AND e.entity_id = i.product_id AND e.entity_type_id = 4') ->joinLeft(array('c' => $  this->getTableName('catalog/product','decimal')), 'c.entity_id=i.product_id and c.attribute_id=79', 'c.value as costing, ((ps.qty - SUM(i.qty_ordered)) * c.value) AS totcsttostock')              ->where('i.parent_item_id is null')              ->where("i.created_at BETWEEN '".$  from."' AND '".$  to."'")              ->where('main_table.state = \'complete\'')              ->columns(array('ordered_qty' => 'count(distinct main_table.entity_id)'));              echo $  this->getSelect();         return $  this;     } 

Please can some one help or suggest anything?