Reg: Function NTILE -

Question

Hi Experts,
I was going through the function(s) in Oracle docs which I have never used, to learn something new.
Got a doubt - What is the actual/practical use of function - NTILE ?
I tried playing with it and understood it's working but a practical example will give a better understanding.
Also, another curious question - What can be the scenario where after distributing the rows equally amount 'x' buckets, the remainder rows are distributed 1 each serially in all buckets?
ranit@XE11GR2>> select * from x1;
      COL1       COL2 COL3                           COL4
         1       1401 a1                             aa1
         2        102 a2                             aa2
         3        103 a3                             aa3
         4        104 a4                             aa4
         5        105 a5                             aa5
         6        101 a1                             aa1
         7        107 a7                             aa7
         8        101 a1                             aa1
         9        109 a9                             aa9
        10        102 a2                             aa2
        11        101 a1                             aa1
        12        101 a1                             aa1
12 rows selected.
Elapsed: 00:00:00.14
ranit@XE11GR2>> select col1, col2, col3, col4,
  2  NTILE(5) OVER(order by col2) nt
  3  from x1;
      COL1       COL2 COL3  COL4           NT
         6        101 a1    aa1             1
        11        101 a1    aa1             1
         8        101 a1    aa1             1
        12        101 a1    aa1             2
        10        102 a2    aa2             2
         2        102 a2    aa2             2
         3        103 a3    aa3             3
         4        104 a4    aa4             3
         5        105 a5    aa5             4
         7        107 a7    aa7             4
         9        109 a9    aa9             5
         1       1401 a1    aa1             5
12 rows selected.
Any help regarding this is much appreciated.
Regards
-- Ranit
(on Oracle version 11.2.0.2.0)

Answer 1

I meant using ntile for computing quantiles.
with
data_table as
(select trunc(dbms_random.value(10,100)) outcome
   from dual
connect by level <= :trials
select outcome,
       ntile_q,
       case when lead(ntile_q) over (order by outcome) - ntile_q > 0
            then 0.5 * (lead(outcome) over (order by outcome) + outcome)
       end q_tile
  from (select outcome,
               ntile(:q) over (order by outcome) ntile_q
          from data_table
order by outcome
OUTCOME
NTILE_Q
Q_TILE
13
1
23
1
28
1
29.5
31
2
36
2
37
2
38.5
40
3
49
3
51
3
53
55
4
57
4
64
4
67
70
5
71
5
76
5
77
78
6
79
6
81
6
87
93
7
97
7
Regards
Etbin