SQL>  create or replace procedure test_1(
  2   en number default null,
  3   sl number default null  ) is
  4       type rfcur is ref cursor;
  5       rf  rfcur;
  6      str varchar2(500);
  7     em1 emp%rowtype;
  8      begin
  9       str :='select * from emp ';
 10      if en is not null or sl is not null then
 11        str :=str||' where ';
 12         if en is not null then
 13          str := str||' empno= '||en||' and ';
 14         end if;
 15        if sl is not null then
 16          str:=str||' sal ='||sl||' and ';
 17        end if;
 18      str := rtrim(str,' and ');
 19      end if;
 20       OPEN rf for str;
 21       loop
 22         fetch rf into em1;
 23         exit when rf%notfound;
 24         dbms_output.put_line(em1.ename);
 25       end loop;
 26  end;
 27  /