How to add Calculated Fields

rbuser

Hi everybody

I have a doubt...please help me

I have a ppreport with tree bands. the first one is a Group header, after
that a detail band and finally a group footer. I have to calculated one
value given two db fields, That ok, But in the group footer band I must Add
the calculated values. I try to do that increasing a variable in the after
print
event of detail band, but the problem is when change a value in the group
header band....Please if someone can helpme... I would appreciate you
Thanks a lot

nardmoseley

Please see the two articles below. I think they will help you to understand
how to perform the calculations in RB.


------------------------------------------------------------------------
TECH TIP: Performing Calculations
------------------------------------------------------------------------

Calculations can be done either on the data access side
or within ReportBuilder.

When designing reports there are always decisions to be made as to
how much processing to do on the data side versus the report side.
Usually doing more on one side can greatly simplify the other. So it is
often a personal choice based on the power and flexibility of the data
and report tools being used.


DataAccess
----------

a. Use SQL - using SQL you can perform many common calculations:

example: Select FirstName + ' ' + LastName As FullName,
Quantity * Price AS Cost,


b. Delphi TDataSets enable you to create a calculated TField object
and use the DataSet.OnCalcFields event

c. Perform any amount of data processing, summarizing, massaging
etc. to build a result set (query or temp table) to feed to the report.


ReportBuilder
-------------

Calculations in ReportBuilder are performed primarily using
the TppVariable component.

a. Set the Variable.DataType

b. Code the calculations using the Variable.OnCalc event.

c. Use the Timing dialog to control the timing of the OnCalc event.
To access the Timing dialog, right click over the Variable
component and select the Timing... option from the speed menu.

d. Set the LookAhead property to True, when you need to display
summary calculations in the title, header, group header, etc.

e. To perform calculations based on the results of other
calculations use the Calc Order dialog of the band. To access
the Calc Order dialog, right click over the Band component
and select the Calc Order... option from the speed menu.


By using TppVariable components ReportBuilder will take care of caching
intermediate results of accumlated calcs that cross pages.

There are a number of calculation examples in the main demos.dpr
project.

---

Additional Notes:

1. Do NOT use Band.BeforePrint or Band.AfterPrint. These events fire
multiple times and therefore should not be used for calculations.

2. Do NOT store results in variables that exist outside of the reports.
For example - form level variables.



--
Tech Support mailto:support@digital-metaphors.com
Digital Metaphors http://www.digital-metaphors.com



------------------------------------------------------
Tech Tip: Calculating a Summary based on Group Totals
------------------------------------------------------

Question: I am using a Variable in the Group Footer to conditionally
calculate totals for each group. I want to add a second Variable to the
Summary that accumulates the results calculated for each group.

The following example uses two Variable components: vCustomerTotal and
vCustomerSummary. The variable vCustomerTotal has its Timing defined to
Reset on GroupEnd.


There are two options for accumulating the summary total.

1. Use the vCustomerTotal OnCalc event to accumulate the detail and the
summary.

example:

procedure vCustomerTotalOnCalc(Sender: TObject; var Value: Variant);
begin

if (plCustomer['Amountpaid'] > 100.00) then
begin
{sum detail}
Value := Value + plCustomer['Amountpaid'];

{accumulate summary}
vCustomerSummary.Value := vCustomerSummary.Value +
plCustomer['Amountpaid'];
end;

end;


2. Set the timing of the Summary OnCalc to "GroupBeforeFooter" and
accumulate the detail variable results. Note that here we use
GroupBeforeFooter because the detail variable has its Reset defined as
"GroupEnd" - implying that if we try to use GroupEnd for our summary
calculation the accumulated results will be 0.

example:

procedure vCustomerTotalOnCalc(Sender: TObject; var Value: Variant);
begin

{sum detail}
if plCustomer['Amountpaid'] > 100.00 then
Value := Value + plCustomer['Amountpaid'];

end;


procedure vCustomerSummaryOnCalc(Sender: TObject; var Value: Variant);
begin

{accumulate summary}
Value := Value + vCustomerTotal.Value;

end;

--