User Interface

Let’s add a Subtotal field to the order. This field will sum up the extended prices of all order details.

In the Project Explorer, switch to Controllers tab. Right-click on Orders / Fields, and press New Field.

The new field’s settings will be:

select sum(UnitPrice*Quantity*(1-Discount)) 
from "Order Details"
where "Order Details".OrderID = Orders.OrderID

Press OK to save the field.

Your application will incorporate this SQL Formula in the SELECT statements composed at runtime. This statement will look similar to:

select *, 
   (
   select sum(UnitPrice*Quantity*(1-Discount)) from "Order Details"
   where "Order Details".OrderID = Orders.OrderID
   ) Subtotal
from 
   "Orders" Orders

This is the output produced when the statement is executed in SQL Management Studio. The actual statement will look more complex, and may include user-defined sorting, filtering, and paging parameters.

We’ll need to bind this field to views, so that the end user can see the field value.

Drop Orders / Fields / Subtotal field node onto Orders / Views / grid1 node.

Drop Subtotal field node onto Orders / Views / editForm1 node.

Drop Subtotal field node onto Orders / Views / createForm1 view node.

Regenerate the application, and select any order on the Order Form page. You will see the Subtotal field showing the sum of extended prices.

The Order Details grid view displays several unnecessary reference fields, such as Order Customer Company Name, Order Employee Last Name, and Order Ship Via Company Name. We will get rid of these redundant fields. Let’s also display the average Unit Price, total Quantity, average Discount, and total sum of Extended Price at the bottom of the grid.

In the Project Explorer, expand to Order Form / c100 / dv101 / grid1 node. Highlight the data fields OrderCustomerCompanyName, OrderEmployeeLastName, and OrderShipViaCompanyName. Right-click and press Delete.

Now that the redundant data fields have been removed, let’s assign aggregates. Double-click on Order Details / Views / grid1 / UnitPrice.

Change the Aggregate Function property:

Press OK to save the data field.

Next, double-click on Quantity data field.

Change the following value:

Save the data field, and double-click on Discount.

Change Aggregate Function to “Average”.

Press OK, and double-click on ExtendedPrice.

Change Aggregate Function to “Sum”.

Press OK to save Extended Price data field.

Generate the application, and navigate to Order Form page. Select any order. You will see that the list of order details will not display redundant order information, and displays aggregates at the bottom of the grid.