Query using NTILE function

Question

Is there any better way to write this query:
SELECT
     MIN(EMPNO) "StartEmpno",
     MAX(EMPNO) "EndEmpno",
     partition
     FROM
     SELECT
               EMPNO,
               NTILE(20) OVER (ORDER BY EMPNO ASC ) as partition
          FROM
               (SELECT
                         EMPNO
                         FROM
                         EMP1
                         WHERE DEPTNO = 20
               GROUP BY EMPNO     
          GROUP BY
          partition

Answer 1

Well, one would assume that a column named empno in the emp table would be unique. If it was unique, the results would have been the same.
Well, this doesn't end up being much different that your original, but I would use distinct in the innermost inline view instead of a grouping one level above that:
select min(empno) "StartEmpno",
       max(empno) "EndEmpno",
       partition
  from (select empno,
               ntile(20) over (order by empno) partition
          from (select distinct empno
                  from emp1
                 where deptno = 20))
group by partition;