Often subreports are used in Crystal Reports to retrieve an unrelated value from a different table or data source. In many of these cases you do not want to see the subreport at all. You just want to retrieve your value and use it. You soon realize, however, that if you suppress the subreport object, or if you suppress the section that contains the subreport, the subreport will simply not run.
To make a subreport run but be completely invisible you suppress all of the sections in the subreport. This makes the subreport completely invisible, but still allows it to run. You could stop here, but the section that contains the subreport will still take up some space on your report, even though it is empty space. Some people just make this section (and the subreport object) very small so that it is hardly noticeable. But go one step further for an even better solution. If you are using version 9 or later, go into the Section Expert for the section that contains the subreport, and chek “Suppress Blank Section”. This will make the section invisible but the subreport will run.
If you are using v8.5 you can set the section in the main report (the section containing the subreport) to “Underlay following sections”. This causes Crystal to superimpose the blank subreport section over whatever will print below the subreport. Now it is both invisible and it doesn’t take up any space. But with this method the section below the subreport must appear at least as frequently as the section containing the subreport. Otherwise the subreport section won’t have anything to hide behind. So I could hide a subreport in Group Header A above a visible Group Header B or even above visible details below the Group Header. However I can’t hide a subreport in the Details section above a Group Footer, because the Group Footer doesn’t print as often as the details.
If you like techniques like this you should check out the Crystal Reports “Expert Techniques” guides in my library.