create or replace trigger emp_bud
before update or delete on emp
for each row
declare
  v_action varchar2(50);
  v_log    varchar2(500) := '';
begin
  if :new.empno is not null then
    begin
      v_log := v_log || '操作' || :new.empno ;
      if :new.ename <> :old.ename then
        v_log := v_log || ' ename 由' || :old.ename || '更改为' || :new.ename;
      end if;
      if :new.job <> :old.job then
        v_log := v_log || ' job 由' || :old.job || '更改为' || :new.job;
      end if;
      if :new.mgr <> :old.mgr then
        v_log := v_log || ' mgr 由' || :old.mgr || '更改为' || :new.mgr;
      end if;
      if :new.hiredate <> :old.hiredate then
        v_log := v_log || ' hiredate 由' || :old.hiredate || '更改为' ||
                 :new.hiredate;
      end if;
      if :new.sal <> :old.sal then
        v_log := v_log || ' sal 由' || :old.sal || '更改为' || :new.sal;
      end if;
      if :new.comm <> :old.comm then
        v_log := v_log || ' comm 由' || :old.comm || '更改为' || :new.comm;
      end if;
      if :new.deptno <> :old.deptno then
        v_log := v_log || ' deptno 由' || :old.deptno || '更改为' || :new.deptno;
      end if;
      if UPDATING then
        v_action := 'update';
      elsif deleting then
        v_action := 'delete';
      end if;
      insert into emp_log
        (id, action, time, log, actor)
      values
        (EMPLOG_SEQ.NEXTVAL, v_action, sysdate, v_log, USER);
      /*pkg_emp.v_emp_obj.empno := :new.empno;
      select *
      into   pkg_emp.v_emp_obj
      from   emp
      where  empno = pkg_emp.v_emp_obj.empno;
      dbms_output.put_line ( 'ename = ' || pkg_emp.v_emp_obj.ename || ' job = ' || pkg_emp.v_emp_obj.job );*/
    exception
      when others then
        dbms_output.put_line(SQLCODE || '-before-' || SQLERRM);
    end;
  else
    pkg_emp.v_emp_obj.empno := 0;
  end if;
end;

?例子： update emp where empno=7369；

注意 ： 本例子中一定要有empno才可以