Magento collection join add alias - mysql

Question

I want Mage_Adminhtml_Block_Dashboard_Orders_Grid setCollection rewrite.
I done :
public function setCollection($collection)
{
$connection = $collection->getConnection();
if(!Mage::helper("accountmanager")->isAdmin()){
$userId = Mage::helper("accountmanager")->getUserId();
$collection->getSelect()->joinInner(array('items_table'=>'sales_flat_order_item'),
'main_table.entity_id = items_table.order_id ',
null);
$collection->getSelect()->joinInner(array('e'=>'catalog_product_entity'),
'items_table.product_id = e.entity_id ',
null);
$collection->getSelect()->joinLeft(array('at_created_by'=>'catalog_product_entity_int'),
'(`at_created_by`.`entity_id` = `e`.`entity_id`) AND (`at_created_by`.`attribute_id` = 141) AND (`at_created_by`.`store_id` = 0) ',
null);
$collection->getSelect()->where("at_created_by.value = '".$userId."'");
}
exit($collection->getSelect());
parent::setCollection($collection);
}
result this:
SELECT `main_table`.*, `main_table`.`total_item_count` AS `items_count`, CONCAT_WS(' ', main_table.customer_firstname, main_table.customer_lastname) AS `customer`, `main_table`.`base_grand_total` AS `revenue` FROM `sales_flat_order` AS `main_table` INNER JOIN `sales_flat_order_item` AS `items_table` ON main_table.entity_id = items_table.order_id INNER JOIN `catalog_product_entity` AS `e` ON items_table.product_id = e.entity_id LEFT JOIN `catalog_product_entity_int` AS `at_created_by` ON (`at_created_by`.`entity_id` = `e`.`entity_id`) AND (`at_created_by`.`attribute_id` = 141) AND (`at_created_by`.`store_id` = 0) WHERE (store_id = '1') AND (at_created_by.value = '3')
this sql error : Error Code: 1052. Champ: 'store_id' dans where clause est ambigu
i think store_id no have alias 'main_table'.
How my query add alias??
please help me.
think you .