Suppressing duplicate values
Frequently, you find that you do not need to display all the data present in a report. For example, sometimes a report column displays duplicate values in consecutive data rows. When the duplication is unnecessary or makes the report difficult to read, you can suppress consecutive duplicate values.
You can use BIRT Studio to suppress duplicate values that appear in a grouped column. For example, a report that lists customer orders, grouped by customer, shows some data values such as the address, contact information, customer number, and so on, multiple times for every order placed by the customer. You can prevent the duplicate occurrence of these values by moving data rows from the column to the group header.

Additional Links:

Copyright Actuate Corporation 2013 BIRT iHub 2