If the Group By Style on the analysis parameters tab is set to User specified, a Group By Rollup element may be dragged onto the empty node under the Group By Clause, giving the following result. If User specified is not checked, a warning is given when the Group By Rollup element is applied that the option will be automatically checked.
Columns can be moved into the folder titled Expressions (but not expressions or column positions), leading to a comma separated list of the columns that define a rollup of report rows across a single logical dimension. If only one column is specified, it is equivalent to an ordinary Group By clause.
In the following example with the tutorial data table twm_customer, a group by rollup of customer_count over a single dimension defined and ordered by gender and marital_ status is requested.
The resulting data is listed in the following table.
The blank spaces in the answer table above represent null values that signify the empty set rather than information that is missing. Through this technique, aggregations at many different levels are shown in a single answer table.
There are no special properties for the Group By Rollup element.