Double entries appearing when adding custom attribute to orders grid

Question

I have added a few custom columns to the sales order grid.

SKU and product name were successfully added, appearing as expected in their respective rows.

Now when I add a product attribute that doesn't come from the sales_flat_order_item table, I get double entries populating for every row for these columns.

=> For example : I add custom_attr from the catalog_product_entity_varchar table. Now all three extra columns are doubled up:

SKU: 123,123

Name: example, example

custom_attr: blue,blue

I think the problem comes from the following code in my Observer, if anyone can spot it?

    $collection = $observer->getOrderGridCollection();
    $select = $collection->getSelect();
    $select->joinLeft(array('payment' => $collection->getTable('sales/order_payment')), 'payment.parent_id=main_table.entity_id', array('payment_method' => 'method'));
    $select->join('m_sales_flat_order_item', '`m_sales_flat_order_item`.order_id=`main_table`.entity_id', array('sku' => new Zend_Db_Expr('group_concat(`m_sales_flat_order_item`.sku SEPARATOR ", ")'),'name'  => new Zend_Db_Expr('group_concat(`m_sales_flat_order_item`.name SEPARATOR ", ")') ));
    $select->join('m_catalog_product_entity_varchar', '`m_catalog_product_entity_varchar`.attribute_id=163 AND `m_catalog_product_entity_varchar`.entity_id = `m_sales_flat_order_item`.`product_id`', array('custom_attr'  => new Zend_Db_Expr('group_concat(`m_catalog_product_entity_varchar`.value SEPARATOR ",")')));
    $select->group('main_table.entity_id');

Update

Thanks to the below responses I was able to reach a solution with a bit modification. The two joins worked as below.

    $select->join('m_sales_flat_order_item','`m_sales_flat_order_item`.order_id=`main_table`.entity_id', array('sku' => new Zend_Db_Expr('`m_sales_flat_order_item`.sku'),'name'  => new Zend_Db_Expr('`m_sales_flat_order_item`.name') ))->where('`m_sales_flat_order_item`.parent_item_id IS NULL');
    $select->join(array('m_catalog_product_entity_varchar'),'(m_catalog_product_entity_varchar.entity_id = `m_sales_flat_order_item`.`product_id`) AND `m_catalog_product_entity_varchar`.attribute_id=163',
array('custom_attr' => 'm_catalog_product_entity_varchar.value'));

Answer 1

@snevet,you need add a condition to collection.

$select->where('`m_sales_flat_order_item`.parent_item_id IS NULL');

Because of when an configurable is ordered,two row insert into sales_flat_item table.One is save simple product id and another configurable product,but tow save same sku which is simple product sku

Answer 2

Try out below below code instead of custom_attr join:

->joinLeft(
    array('m_catalog_product_entity_varchar'),
    '(m_catalog_product_entity_varchar.entity_id = `m_sales_flat_order_item`.`product_id`) AND `m_catalog_product_entity_varchar`.attribute_id=163',
    array('custom_attr' => m_catalog_product_entity_varchar.value)
)