A subreport is a report within a report. With subreports, unrelated reports can be combined into a single report. You can coordinate data that could not otherwise be linked, or you can present different views of the same data in a single report.
If your report has a section that handles a large number of records, you can put that section into an on-demand subreport. An on-demand subreport appears as a hyperlink in the primary report. When you open the primary report, no data is retrieved for the on-demand subreport until you drill down on the hyperlink.
Tip Whenever possible, coordinate your report data by linking database tables with the Visual Linking Expert, rather than by linking regular subreports that is, subreports that aren't on-demand subreports to the main report. Since each subreport is run as a separate report, linked tables often have a performance advantage.
To insert a subreport
Note Using on-demand subreports will increase the performance of reports that contains subreports.
When you run the report, the program will coordinate the data in the primary report with the data in the subreport.
Note The field type of the Containing Report field determines which subreport fields are visible. Because the Crystal Reports ActiveX Designer reads dates as either strings, dates, or date/time fields, you must make sure your subreport parameter field type matches the field type set up in Report Options in the main report for the field you want linked.