Ttdfjt

I used many update methods for update values in sales_flat_order and sales_flat_order_grid tables, but no method didn't work.

I don't know why the update is not done.

Method 1:-

$coreResource = Mage::getSingleton('core/resource');
$write = $coreResource->getConnection('core_write');
 $_field_flat_order =array();
 $_field_flat_order['grand_total'] = $order_gt;
 $_field_flat_order['base_grand_total'] = $order_gt;
 $_field_flat_order['discount_amount'] = $order_discount;
 $_field_flat_order['base_discount_amount'] = $order_discount;
 $_field_flat_order['discount_description'] = "1%";
 $write->update($coreResource->getTableName('sales_flat_order'),$_field_flat_order,array('entity_id = ?' => $order_id,));

Method 2:-

$order_data=Mage::getModel('sales/order')->loadByIncrementId($increment_id);
 $order_data->setGrandTotal($order_gt);
 $order_data->setBaseGrandTotal($order_gt);
 $order_data->setBaseDiscountAmount($order_discount);
 $order_data->setDiscountAmount($order_discount);
 $order_data->setDiscountDescription("1%");
 $order_data->save();

Method 3 :-

$sql_order = "UPDATE sales_flat_order SET grand_total='".$order_gt."',base_grand_total='".$order_gt."',discount_amount='".$order_discount."',base_discount_amount='".$order_discount."',discount_description='1%' WHERE entity_id ='".$order_id."'";
$write->query($sql_order);

No method didn't work, but all other tables are updating perfectly.

Anyone know the reason.?

Try:

<?php $write = Mage::getSingleton('core/resource')->getConnection('core_write'); ?>

And:

<?php
$write->query("UPDATE sales_flat_order SET grand_total = '$order_gt', base_grand_total = '$order_gt', discount_amount = '$order_discount', base_discount_amount = '$order_discount', discount_description ='1%' WHERE entity_id = '$order_id'");
?>

Having in mind that "While creating invoice to particular order, We can't update sales order tables for that particular order.", you can update that order getting it from the observer Example:

config.xml
...

<events>
 <sales_order_invoice_save_after>
 <observers>
 <unique_identifier>
 <type>singleton</type>
 <class>Module_SalesOrder_Model_Observer</class>
 <method>updateDeliveryDate</method>
 </unique_identifier>
 </observers>
 </sales_order_invoice_save_after>
</events>

...

Observer

class Module_SalesOrder_Model_Observer

 public function updateDeliveryDate(Varien_Event_Observer $observer) 
 $_event = $observer->getEvent();
 $_invoice = $_event->getInvoice();
 $_order = $_invoice->getOrder();

 $_order->setDeliveryAt('2018-03-26 00:00:00');
 $_order->save();