How to rollback last executed sql script fired as sysdba

The 'gotcha' is that in nearly every case you really don't want to take the performance and maintenance hit for triggers just to hide the pk insert.

You really should write the queries to insert sequence.nextval with the INSERT. Do it during the migration before you regret it a few years from now.

This can be done in a single statement, but you have to wrap the sequence call in a function.

By calling a function in the select (as opposed to the sequence directly), you overcome the problem of getting ORA-02287 errors. However, the function will be called once for each row in A, which is not what you want.

This can be overcome by defining the function as deterministic. This allows Oracle to optimize the function so it is only executed once for each distinct parameter value passed in. To make this work in this case, you'll need to pass in ceil(x/2):

create or replace function f(p integer) return number deterministic  as
  l_retval pls_integer;
begin
  select my_seq.nextval into l_retval from dual;
  return l_retval;
end;
/

insert all 
    when mod(x,2) = 0 then
        into b (val) values (seq)
        into c (val) values (seq)
    else 
        into c (val) values (seq)
select x, f(ceil(x/2)) seq from a;


select * from b;

VAL
---
  1 
  2 

select * from c;

VAL
---
  1 
  2 
  1 
  2