有变量和运算的存储过程 

 -- have variable and minus 运算的存储 procedure 
  create or replace procedure testtime
  is 
  n_start number;
  n_end number;
  samplenum number;
  use_time number;
  begin
    n_start:=dbms_utility.get_time;
    select count(*) into samplenum from emp;
    n_end:=dbms_utility.get_time;
    use_time:= n_end - n_start;
    dbms_output.put_line('this statement cost '|| use_time ||' miliseconds');
    end;