Oracle instead of triggers, and why you need them:

You cant update a view if it contains:
group by
order by
analytical /aggregate functions
subqueries
joins

You then need an ‘instead of’ trigger

CREATE TRIGGER my_trigger
 INSTEAD OF INSERT ON my_view
 FOR EACH ROW
 DECLARE
    -- stuff
 BEGIN
   INSERT INTO table_a VALUES (
         :NEW.col_a,
         :NEW.col_b);
   -- etc
 COMMIT;
 END;