SQL in a Nutshell, 3rd Edition

Name

PERCENT_RANK

Generates a relative rank for a hypothetical row by dividing that row’s rank less 1 by the number of rows in the group.

ANSI SQL Standard Syntax

PERCENT_RANK(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 syntax:

PERCENT_RANK(  ) 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 PERCENT_RANK aggregate function.

Example

The following example determines the percentage 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, PERCENT_RANK(4,1) WITHIN GROUP (ORDER BY num, odd)
FROM test4 GROUP BY odd;
       ODD PERCENT_RANK(4,1)WITHINGROUP(ORDERBYNUM,ODD)
---------- --------------------------------------------
         0                                            1
         1                                          .75

In the group odd=0, the new row comes after (0,0), (2,0), and (4,0), and thus it is in position 4. The rank computation is (4th rank - 1)/3 rows = 100%. In the group ...