How to get the first or last row value from a group using ntile

Question

I want to query and use ntile to divide by data in 4 groups (quartiles). I got this part no problem and it returns the list of rows and the ntile bucket value for each one.
What I want though is to get only the first row from each ntile group (so in effect the max, q3, median, q1 and min values from the whole result). Of course I coud get max, min and median directly using the other functions, but how about the values for q3 and q1?
My query contains this:
NTILE(4) OVER (ORDER BY salary DESC NULLS LAST) as ntile
So I want the highest, lowest, middle, q3 and q1 values for the salaries.
Should I be using NTILE, ROWNUM, PERCENTIL_DIST....?
Any ideas? Thanks in advance.

Answer 1

SQL> select ename,sal,
  2  NTILE(4) OVER (ORDER BY sal DESC NULLS LAST) as ntile
  3  from emp
  4  /
ENAME             SAL      NTILE
KING             5000          1
FORD             3000          1
SCOTT            3000          1
JONES            2975          1
BLAKE            2850          2
CLARK            2450          2
ALLEN            1600          2
TURNER           1500          2
MILLER           1300          3
WARD             1250          3
MARTIN           1250          3
ENAME             SAL      NTILE
ADAMS            1100          4
JAMES             950          4
SMITH             800          4
14 rows selected.
SQL> select  ename,
  2          sal
  3    from  (
  4           select  ename,
  5                   sal,
  6                   ROW_NUMBER() OVER (PARTITION BY ntile ORDER BY sal DESC NULLS LAST) as rn
  7             from  (
  8                    select  ename,
  9                            sal,
10                            NTILE(4) OVER (ORDER BY sal DESC NULLS LAST) as ntile
11                      from  emp
12                   )
13          )
14    where rn = 1
15  /
ENAME             SAL
KING             5000
BLAKE            2850
MILLER           1300
ADAMS            1100
SQL> SY.