Crystal Reports 10: The Complete Reference

Subreports create potential performance problems for your reporting projects. Here are some tips to help maximize performance for your report viewer. Obviously, these considerations are more important if a viewer will be viewing a report online using Crystal Reports or as an on-demand report on the Web with Crystal Enterprise. If a report is being printed or exported, subreports affect performance as well, but the user won t be staring at the screen waiting for them.

• Use on-demand subreports if you can. That way, a viewer won t have to wait for many subreports to process. Viewers can click the individual subreports they want to see when they want to see them.

• If you are creating a linked subreport, try to base the link on an indexed field in the subreport. This will cause record selection in the subreport to occur substantially faster. If the subreport is based on an ODBC or SQL database, make sure you are keeping as much of the SQL query on the server as possible (see Chapter 16 for SQL database performance considerations).

• If you are linking subreports with formula fields, try to keep the formula field in the main report and use a database field in the subreport. Using formula fields in the subreport, particularly with subreports based on SQL databases, will move part or all of the subreport query off the server, impeding performance.