create or replace trigger id_fill_trig
before insert on my_test_table
for each row
BEGIN
  :NEW.id := test_seq.nextval;
END;
/

SQL> insert into my_test_table
  2  values (12312,EMPTY_CLOB(),EMPTY_BLOB(),'test3',sysdate,null);

1 row created.

SQL> insert into my_test_table
  2  values (1124,EMPTY_CLOB(),EMPTY_BLOB(),'test3',sysdate,null);

1 row created.

SQL> select id from my_test_table;

        ID
----------
       214
       215

SQL> insert into my_test_table
  2  values (dy_0001_test_seq.nextval,EMPTY_CLOB(),EMPTY_BLOB(),'test3',sysdate,
null);

1 row created.

SQL> select id from my_test_table;

        ID
----------
       214
       215
       217

SQL>