SQL in a Nutshell, 3rd Edition

Name

CUME_DIST

Computes the relative rank of a hypothetical row within a group of rows, using the following equation:

(rows_preceding_hypothetical + rows_peered_with_hypothetical) / rows_in_group

Bear in mind that the rows_in_group value includes the hypothetical row that you are proposing when you call the function.

ANSI SQL Standard Syntax

CUME_DIST(value_list) WITHIN GROUP (ORDER BY sort_list)
value_list ::= expression[, expression...]
sort_list ::= sort_item[, sort_item...]
sort_item ::= expression [ASC | DESC] [NULLS FIRST | NULLS LAST]

Items in the value_list correspond by position to items in the sort_list. Therefore, both lists must have the same number of expressions.

Oracle

Oracle follows the ANSI SQL syntax and implements the following analytic syntax:

CUME_DIST(  ) OVER ([partioning] ordering)

For an explanation of the partioning and order clauses, see the section later in this chapter titled “ANSI SQL Window Functions.”

MySQL, PostgreSQL, and SQL Server

These platforms do not implement the CUME_DIST aggregate function.

Example

The following example determines the relative rank of the hypothetical new row (num=4, odd=1) within each group of rows from test4, where groups are distinguished by the values in the odd column:

SELECT * FROM test4;
       NUM        ODD
---------- ----------
         0          0
         1          1
         2          0
         3          1
         3          1
         4          0
         5          1

SELECT odd, CUME_DIST(4,1) WITHIN GROUP (ORDER BY num, odd)
FROM test4 GROUP BY odd; ODD CUME_DIST(4,1)WITHINGROUP(ORDERBYNUM,ODD) ---------- ----------------------------------------- 0 1 ...