This documentation is related to an older version of Firebolt. For the most current documentation, see Firebolt documentation.

PERCENT_RANK

Calculates the relative rank of the current row within an ordered data set, as ( rank - 1 ) / ( rows - 1 ) where rank is the current row’s rank within the partition, and rows is the number of rows in the partition. PERCENT_RANK always returns values from 0 to 1 inclusive. The first row in any set has a PERCENT_RANK of 0.

See also CUME_DIST, which returns the cumulative distribution of the current row in relation to other rows in the same partition within an ordered data set.

Syntax

PERCENT_RANK() OVER ( [ PARTITION BY <val> ] ORDER BY <expr> [ASC|DESC] )

The return type of the function is DOUBLE. This function respects NULL values, and results will be ordered with default null ordering NULLS LAST unless otherwise specified in the ORDER BY clause.

Example

The example below calculates, for each student in grade nine, the percent rank of the student’s test score by their grade level.

SELECT
	first_name, test_score,
	PERCENT_RANK() OVER (PARTITION BY grade_level ORDER BY test_score DESC) as percent_rank
FROM
	class_test
WHERE grade_level=9;

Returns:

' +------------+------------+---------------------+
' | first_name | test_score |    percent_rank     |
' +------------+------------+---------------------+
' | Humphrey   |         90 |                   0 |
' | Sammy      |         85 |                 0.2 |
' | Peter      |         80 |                 0.4 |
' | Iris       |         79 |                 0.6 |
' | Jojo       |         78 |                 0.8 |
' | Frank      |         76 |                   1 |
' +------------+------------+---------------------+