ntile：
NTILE is an analytic function. It divides an ordered data set into a number of buckets indicated by expr and assigns the appropriate bucket number to each row. The buckets are numbered 1 through expr. The expr value must resolve to a positive constant for each partition. Oracle Database expects an integer, and if expr is a noninteger constant, then Oracle truncates the value to an integer. The return value is NUMBER.
The number of rows in the buckets can differ by at most 1. The remainder values (the remainder of number of rows divided by buckets) are distributed one for each bucket, starting with bucket 1.
If expr is greater than the number of rows, then a number of buckets equal to the number of rows will be filled, and the remaining buckets will be empty.
示例：
SQL> select empno,sal, ntile(4) over(order by sal desc) as order_quartitle from
check_test;
EMPNO SAL ORDER_QUARTITLE
---------- ---------- ---------------
7839 5000 1
7902 3000 1
7788 3000 1
7566 2975 1
7698 2850 2
7782 2450 2
7499 1600 2
7844 1500 2
7934 1300 3
7521 1250 3
7654 1250 3
EMPNO SAL ORDER_QUARTITLE
---------- ---------- ---------------
7876 1100 4
7900 950 4
7369 800 4
width_bucket：
伪sql：width_bucket(<expression or column>,<lower bound>,<lower bound>,<number of buckets>)
SQL> select empno,
2 sum(sal) as t_sal,
3 width_bucket(sum(sal), 0, 5001, 6) as t_bucket
4 from check_test t
5 group by t.empno
6 ;
EMPNO T_SAL T_BUCKET
----- ---------- ----------
7782 2450 3
7839 5000 6
7844 1500 2
7698 2850 4
7521 1250 2
7902 3000 4
7566 2975 4
7654 1250 2
7788 3000 4
7934 1300 2
7499 1600 2
7876 1100 2
7369 800 1
7900 950 2
原文：http://www.cnblogs.com/evancao350/p/4599213.html