Leveraging the Database - Oracle APEX Best Practices - page 78

This query can be written with the GROUPING SETS clause as follows:
As you can see in lines 6 through 11, with the GROUPING SETS clause you have more
granular control, but it can be quite verbose. The Cube clause is compacter and
processes equivalent results.
Identifying the totals and subtotals with grouping
In the result sets you might notice that it can be confusing to detect which rows in
the result set are the aggregated records and which are not. Oracle did recognize the
need to identify the aggregated records and created some support functions to do so.
These functions are Grouping , Grouping_id , and Group_id .