create sequence product_log_seq     minvalue 1 maxvalue 99999999
increment by 1
start with 1;

create or replace trigger "product_log_tri"
  before insert 
    on "i_product_log"
    referencing new as new old as old
    for each row
      begin
          select prodcut_log_seq.nextval into :new.pl_id from dual;
      end;