ORA-01792 appears to be a logical error which means you are attempting to create a table or view with more than 1000 columns or adding columns to an existing table or view resulting in 1000+ columns, however if you are on 12cR1 and above and receiving ORA-01792 from a Select statement then this can be due to unpublished bugs:-
- Bug 19653859 – CI BACKPORT OF BUG 19509982 FOR INCLUSION IN DATABASE BP 126.96.36.199.2.
- Bug 19509982 – DISABLE FIX FOR RAISING ORA-1792 BY DEFAULT.
The workaround is either to apply patch 19509982 or to disable fix control 17376322 :-
alter system set "_fix_control"='17376322:OFF';