PERCENT_RANK function [Analytical]

Computes the (fractional) position of one row returned from a query with respect to the other rows returned by the query, as defined by the ORDER BY clause. Returns a decimal value between 0 and 1.

PERCENT_RANK () OVER ( ORDER BY expression [ ASC | DESC ] )

The following statement illustrates the use of the PERCENT_RANK function:

SELECT s_suppkey, SUM(s_acctBal) AS sum_acctBal,
PERCENT_RANK() OVER ( ORDER BY SUM(s_acctBal) DESC )
AS percent_rank_all FROM supplier GROUP BY s_suppkey;

s_suppkey        sum_acctBal       percent_rank_all
supplier#011     200000            0
supplier#002     200000            0
supplier#013     123000            0.3333
supplier#004     110000            0.5
supplier#035     110000            0.5
supplier#006     50000             0.8333
supplier#021     10000             1

PERCENT_RANK is a rank analytical function. The percent rank of a row R is defined as the rank of a row in the groups specified in the OVER clause minus one divided by the number of total rows in the groups specified in the OVER clause minus one. PERCENT_RANK returns a value between 0 and 1. The first row has a percent rank of zero.

The PERCENT_RANK of a row is calculated as

(Rx - 1) / (NtotalRow - 1)

where Rx is the rank position of a row in the group and NtotalRow is the total number of rows in the group specified by the OVER clause.

PERCENT_RANK requires an OVER (ORDER BY) clause. The ORDER BY clause specifies the parameter on which ranking is performed and the order in which the rows are sorted in each group. This ORDER BY clause is used only within the OVER clause and is not an ORDER BY for the SELECT. No aggregation functions in the rank query are allowed to specify DISTINCT.

The OVER clause indicates that the function operates on a query result set. The result set is the rows that are returned after the FROM, WHERE, GROUP BY, and HAVING clauses have all been evaluated. The OVER clause defines the data set of the rows to include in the computation of the rank analytical function.

The ASC or DESC parameter specifies the ordering sequence ascending or descending. Ascending order is the default.

PERCENT_RANK is allowed only in the select list of a SELECT or INSERT statement or in the ORDER BY clause of the SELECT statement. PERCENT_RANK can be in a view or a union. The PERCENT_RANK function cannot be used in a subquery, a HAVING clause, or in the select list of an UPDATE or DELETE statement. Only one rank analytical function is allowed per query.