Unfortunately, you cannot use UPDATE statements on temporary tables, so I believe that is the reason you are recieving an error. An explanation and overview of Temporary Tables can be found [here](https://community.denodo.com/docs/html/browse/6.0/vdp/administration/creating_views/temporary_tables/temporary_tables) if you wish to take a quick look.
Regarding sub-totals, what I would do is create a base view with the subtotals and other fields first. Then I would make a Selection view on top of that first base view, with the 'totals' as an additional calculated field. For reporting, I would use that '2nd' base view with the 'totals' calculated.
Hope this helps!