I was asked about this feature today and noticed that I had never mentioned it in my blog. It is a strange feature because you can turn it on in most reports and yet in most reports it will do absolutely nothing. But when you get it to work it can greatly improve the performance of the report. You will find this option in the database menu.
So what does it do? It tells the database to do the grouping and subtotals. The database will only return one summary record for each group. Check the SQL statement and you will see a GROUP BY clause at the end. This is useful when you have huge amounts of data to process and when you don’t need to show any detail level values. But, this feature only works in reports that meets some very specific criteria.
Things you must do:
Group on a database field or a SQL expression (not a formula)
Hide or suppress the details
Make all of the visible fields either a group field or a summary field
Limit the summaries used to those supported by your Database
(Sum, count, minimum and maximum should be safe in all databases)
Things you must NOT do:
Use specified order grouping.
Add running totals using detail fields.
Add summaries using formulas fields.
If your report meets these criteria, Crystal should be able to add the GROUP BY to your SQL statement, get the server to group the records and calculate all of the summary fields. Use the Show SQL option to confirm the GROUP BY appears.