Friday, March 16, 2012

Total and Subtotal: Creating Subtotal Field

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.

Creating a new field for Orders controller

The new field’s settings will be:

Property Text
Field Name Subtotal
Type Currency
The value of this field is computed at run-time by SQL Expression True
SQL
select sum(unitprice*quantity*(1-discount)) from "order details"
where "Order Details".OrderID = Orders.OrderID
Label Subtotal
Values of this field cannot be edited True
Data Format String c

New 'Subtotal' field settings in Code On Time Designer

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.

Simplified statement of 'Subtotal' SQL Formula calculation in SQL Management Studio

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

On the field’s page, switch to the Data Fields tab. On the action bar, press New | New Data Field. Enter the following settings:

Property Text
View editForm1
Category Orders

New 'Subtotal' Data Field in editForm1

Press OK to save the data field. Double-click on the field in the Project Explorer to go back to the list of data fields. Create another data field with the following settings:

Property Text
View createForm1
Category New Orders

New 'Subtotal' Data Field in createForm1

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

'Subtotal' Field displayed in Order Form page of web application

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