CREATE TABLE new_table as select <do the update "here"> from old_table;

create table test_127 (col_1  number);

insert into test_127 (select level from dual connect by level <= 1000000);

declare
  v_iter   pls_integer := 10;
  v_time   pls_integer;
  v_tot    pls_integer := 0;
begin
 
  for i in 1..v_iter loop
    v_time := dbms_utility.get_time;
    execute immediate 'alter table test_127 add (col_2 number default 0)';
    v_tot := v_tot + (dbms_utility.get_time - v_time);

    execute immediate 'alter table test_127 drop column col_2';
  end loop;

  dbms_output.put_line('Test 1 '||to_char(v_tot));
  
  v_tot := 0
  for i in 1..v_iter loop
    v_time := dbms_utility.get_time;
    execute immediate 'alter table test_127 add (col_2 number)';
    
    execute immediate 'update test_127 set col_2 = 0';
    v_tot := v_tot + (dbms_utility.get_time - v_time);

    execute immediate 'alter table test_127 drop column col_2';
  end loop;

  dbms_output.put_line('Test 2 '||to_char(v_tot));  
end;
/