SQL Server create grand total row

Question

I have a table that contains order details. How can I create a row at the end that totals all my subtotals?

SELECT 
    o.order_id, o.itemDescription as Description, 
    o.quantity_shipped as [Quantity], 
    o.itemCost as [Price each], 
    (o.quantity_shipped * CAST(o.itemCost as float)) as [Sub Total] 
FROM 
    dbo.order_items o

Answer 1

This will give you total by Order Id

SELECT o.order_id, SUM((o.quantity_shipped * CAST    (o.itemCost as float))) as [TotalByOrderId] 
    FROM   dbo.order_items o
    GROUP BY o.order_id

This will give you grand total

SELECT SUM((o.quantity_shipped * CAST    (o.itemCost as float))) as [GrandTotal] 
FROM   dbo.order_items o