1.
for rec in
(select * from all_objects)
loop
    тут выводим первую строчку
    exit;
end loop;

2. тут и так одна строка
select * from dual

SQL> ed
Wrote file afiedt.buf

  1  select
  2   max(empno) KEEP (DENSE_RANK FIRST ORDER BY rownum) empno
  3  ,max(ename) KEEP (DENSE_RANK FIRST ORDER BY rownum) ename
  4  ,max(sal) KEEP (DENSE_RANK FIRST ORDER BY rownum) sal
  5  --другие поля
  6* from emp
SQL> /

     EMPNO ENAME             SAL
---------- ---------- ----------
      7369 SMITH             800