getTable('sales/invoice'); $installer->getConnection() ->addColumn($invoiceTable, 'discount_description', array( 'type' => Varien_Db_Ddl_Table::TYPE_TEXT, 'length' => 255, 'comment' => 'Discount Description' )); $creditmemoTable = $installer->getTable('sales/creditmemo'); $installer->getConnection() ->addColumn($creditmemoTable, 'discount_description', array( 'type' => Varien_Db_Ddl_Table::TYPE_TEXT, 'length' => 255, 'comment' => 'Discount Description' ));