/*1.1*/

select e.ename,e.hiredate 

from emp e

where e.hiredate=(select min(hiredate) from emp)

union all

select e.ename,e.hiredate 

from emp e

where e.hiredate=(select max(hiredate) from emp);

select e.ename,e.hiredate 

from emp e

where e.hiredate in ((select min(hiredate) from emp),(select max(hiredate) from emp));

SELECT ENAME, T.HIREDATE
  FROM EMP T
 WHERE NOT EXISTS (SELECT 1 FROM EMP T1 WHERE T1.HIREDATE < T.HIREDATE)
    OR NOT EXISTS
 (SELECT 1 FROM EMP T1 WHERE T1.HIREDATE > T.HIREDATE)