suresh,

Try this: -

select OrderFormNo

,ClientName

,OrderDate

,Product

,sum(Value)

,InvoiceQuantity

,PendingQuantity

from AOM_Tbl_PendingOrders

group by OrderFormNo, ClientName,OrderDate,Product,InvoiceQuantity,PendingQuantity

In your case, remember that whenever you use the group by clause you need to add all the other colums as well except the function column (i.e. sum)