Grouping rows
You can group related rows together and, optionally, calculate
statistics for each group separately. For example, you might want to
group employee information by department and get total salaries for each
department.
How groups are defined
Each group is defined by one or more DataWindow object columns.
Each time the value in a grouping column changes, a break occurs and a
new section begins.
For each group, you can:
-
Display the rows in each section
-
Specify the information you want to display at the beginning
and end of each section -
Specify page breaks after each break in the data
-
Reset the page number after each break
Grouping example
The following DataWindow object retrieves employee information. It
has one group defined, Dept_ID, so it groups rows into sections
according to the value in the Dept_ID column. In addition, it
displays:
-
Department ID before the first row for that department
-
Totals and averages for salary and salary plus benefits (a
computed column) for each department -
Grand totals for the company at the end
The following screenshot shows the DataWindow object.
How to do it
You can create a grouped DataWindow object in three ways:
-
Use the Group presentation style to create a grouped
DataWindow object from scratch (Using the
Group presentation style). -
Take an existing tabular DataWindow object and define grouping
(Defining
groups in an existing DataWindow object). -
Use the TreeView presentation style (Working with TreeViews).
Making the DataWindow control large
enough
If a DataWindow object has grouped rows, each page contains all
group headers (including zero-height headers) at the top of the page.
Your DataWindow control must be large enough to accommodate all the
group headers that display on each page of the report.
The last row of a group displays on the same page as that row’s
group trailer and each applicable higher-level group trailer. If the
DataWindow object has a summary band, it displays on the same page as
the last row of the report. If the control is not large enough, you
might see anomalies when scrolling through the DataWindow object,
particularly in the last row of the report, which needs room to display
the report’s header band, all group headers, all group trailers, the
summary band, and the footer band.
If you cannot increase the height of the DataWindow control so
that it has room for all the headers and trailers, you can change the
design of the DataWindow object so that they require less space.
Scrolling through a grouped
DataWindow
When you scroll through a grouped DataWindow object, you might see
the group header repeated where you do not expect it. This is because
the data is paginated in a fixed layout based on the size of the
DataWindow control. You can scroll to a point that shows the bottom half
of one page and the top of the next. When you use the arrow keys to page
through the data, you scroll one row at a time.