Oracle9i SQL Reference Release 2 (9.2) Part Number A9654002 


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percentile_disc::=
See Also:
"Analytic Functions" for information on syntax, semantics, and restrictions of the 
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.
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
function sorts the values of the expression in the ORDER
BY
clause, and returns the one with the smallest CUME_DIST
value (with respect to the same sort specification) that is greater than or equal to P
.
See aggregate example for PERCENTILE_CONT.
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.