PERCENTILE_DISC

Syntax

Purpose

PERCENTILE_DISC is an inverse distribution function that assumes a discrete distribution model. It takes a percentile value and a sort specification and returns an element from the set. Nulls are ignored in the calculation.

This function takes as an argument any numeric datatype or any nonnumeric datatype that can be implicitly converted to a numeric datatype. The function returns the same datatype as the numeric datatype of the argument.

The first expr must evaluate to a numeric value between 0 and 1, because it is a percentile value. This expression must be constant within each aggregate group. The ORDER BY clause takes a single expression that can be of any type that can be sorted.

For a given percentile value P, PERCENTILE_DISC sorts the values of the expression in the ORDER BY clause and returns the value with the smallest CUME_DIST value (with respect to the same sort specification) that is greater than or equal to P.

Aggregate Example

See aggregate example for PERCENTILE_CONT.

Analytic Example

The following example calculates the median discrete percentile of the salary of each employee in the sample table hr.employees:

SELECT last_name, salary, department_id,
 PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY salary DESC)
 OVER (PARTITION BY department_id) "Percentile_Disc",
 CUME_DIST() OVER (PARTITION BY department_id 
 ORDER BY salary DESC) "Cume_Dist"
FROM employees where department_id in (30, 60);
LAST_NAME SALARY DEPARTMENT_ID Percentile_Disc Cume_Dist
------------- ---------- ------------- --------------- ----------
Raphaely 11000 30 2900 .166666667
Khoo 3100 30 2900 .333333333
Baida 2900 30 2900 .5
Tobias 2800 30 2900 .666666667
Himuro 2600 30 2900 .833333333
Colmenares 2500 30 2900 1
Hunold 9000 60 4800 .2
Ernst 6000 60 4800 .4
Austin 4800 60 4800 .8
Pataballa 4800 60 4800 .8
Lorentz 4200 60 4800 1

The median value for Department 30 is 2900, which is the value whose corresponding percentile (Cume_Dist) is the smallest value greater than or equal to 0.5. The median value for Department 60 is 4800, which is the value whose corresponding percentile is the smallest value greater than or equal to 0.5.