The best way to make a calculation inside a report is to use a TppVariable component. Simply place the TppVariable component on the report and use its OnCalc event to make the calculation. Take a look at the following article for more information.
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.
Comments
The best way to make a calculation inside a report is to use a TppVariable
component. Simply place the TppVariable component on the report and use its
OnCalc event to make the calculation. Take a look at the following article
for more information.
------------------------------------------------------------------------
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.
--
Regards,
Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com
Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com