Software Platform User guide

report, no data is retrieved for the on-demand subreport until you drill down
on the hyperlink.
For example, when designing a report that shows each employee's quarterly
sales for each product and each product type, you might also want to track
each employee's progress by including weekly sales information. This
additional data, however, may not be of interest to many users viewing the
report. In such a case, extract the weekly sales portion of the report and
attach it as an on-demand subreport. Detailed information about weekly sales
is retrieved from the database only when a user drills down on the on-demand
subreport.
Many report objects—such as large cross-tabs, OLAP grids, advanced charts,
and maps—are ideal candidates to include in on-demand subreports, so that
the object is not processed until you drill down.
To insert an on-demand subreport, see Inserting subreports and Creating
an on-demand subreport.
Tip:
You could also place such report objects in a hidden Details section of a
report that uses the Perform Grouping On Server option. When you do this,
the database server performs the majority of the processing, and only a
subset of the records is transferred from the server to the local machine
(other records are retrieved when you drill down to a hidden section).
Using linked subreports
When a subreport is linked, Crystal Reports coordinates the data in the
subreport with the matching records in the primary report. If you need to use
regular linked subreports—that is, linked subreports that are not on-demand
subreports—you should consider these guidelines:
• If the additional data provided by a regular linked subreport is useful to
relatively few users, create a linked on-demand subreport instead. Users
who need to see the extra data click a hyperlink to view the subreport;
users who don't need to see the extra data won't have to download it from
the database server.
• In some cases, placing regular linked subreports in the Details section of
a main report may hinder performance—especially when your main report
contains many records. (This is because you're creating a separate
subreport for each record, and a separate query must be run for each
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Designing Optimized Web Reports
Making the right design choices