PERCENTILE_DISC (Transact-SQL)

APPLIES TO: yesSQL Server (starting with 2012) yesAzure SQL Database yesAzure SQL Data Warehouse yesParallel Data Warehouse

Computes a specific percentile for sorted values in an entire rowset or within a rowset's distinct partitions in SQL Server. For a given percentile value P, PERCENTILE_DISC sorts the expression values in the ORDER BY clause. It then returns the value with the smallest CUME_DIST value given (with respect to the same sort specification) that is greater than or equal to P. For example, PERCENTILE_DISC (0.5) will compute the 50th percentile (that is, the median) of an expression. PERCENTILE_DISC calculates the percentile based on a discrete distribution of the column values. The result is equal to a specific column value.

Article link icon Transact-SQL Syntax Conventions (Transact-SQL)

Syntax

PERCENTILE_DISC ( numeric_literal ) WITHIN GROUP ( ORDER BY order_by_expression [ ASC | DESC ] )  
    OVER ( [ <partition_by_clause> ] )  

Arguments

literal
The percentile to compute. The value must range between 0.0 and 1.0.

WITHIN GROUP ( ORDER BY order_by_expression [ ASC | DESC)**
Specifies a list of values to sort and compute the percentile over. Only one order_by_expression is allowed. The default sort order is ascending. The list of values can be of any of the data types that are valid for the sort operation.

OVER ( <partition_by_clause>)**
Divides the FROM clause's result set into partitions. The percentile function is applied to these partitions. For more information, see OVER Clause (Transact-SQL). The <ORDER BY clause> and <rows or range clause>can't be specified in a PERCENTILE_DISC function.

Return Types

The return type is determined by the order_by_expression type.

Compatibility Support

Under compatibility level 110 and higher, WITHIN GROUP is a reserved keyword. For more information, see ALTER DATABASE Compatibility Level (Transact-SQL).

General Remarks

Any nulls in the data set are ignored.

PERCENTILE_DISC is nondeterministic. For more information, see Deterministic and Nondeterministic Functions.

Examples

Basic syntax example

The following example uses PERCENTILE_CONT and PERCENTILE_DISC to find each department's median employee salary. They may not return the same value:

  • PERCENTILE_CONT returns the appropriate value, even if it doesn't exist in the data set.
  • PERCENTILE_DISC returns an actual set value.
USE AdventureWorks2012;  
  
SELECT DISTINCT Name AS DepartmentName  
      ,PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY ph.Rate)   
                            OVER (PARTITION BY Name) AS MedianCont  
      ,PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY ph.Rate)   
                            OVER (PARTITION BY Name) AS MedianDisc  
FROM HumanResources.Department AS d  
INNER JOIN HumanResources.EmployeeDepartmentHistory AS dh   
    ON dh.DepartmentID = d.DepartmentID  
INNER JOIN HumanResources.EmployeePayHistory AS ph  
    ON ph.BusinessEntityID = dh.BusinessEntityID  
WHERE dh.EndDate IS NULL;  

Here is a partial result set.

DepartmentName        MedianCont    MedianDisc
--------------------   ----------   ----------
Document Control       16.8269      16.8269
Engineering            34.375       32.6923
Executive              54.32695     48.5577
Human Resources        17.427850    16.5865

Examples: Azure SQL Data Warehouse and Parallel Data Warehouse

Basic syntax example

The following example uses PERCENTILE_CONT and PERCENTILE_DISC to find each department's median employee salary. They may not return the same value:

  • PERCENTILE_CONT returns the appropriate value, even if it doesn't exist in the data set.
  • PERCENTILE_DISC returns an actual set value.
-- Uses AdventureWorks  
  
SELECT DISTINCT DepartmentName  
       ,PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY BaseRate)  
        OVER (PARTITION BY DepartmentName) AS MedianCont  
       ,PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY BaseRate)  
        OVER (PARTITION BY DepartmentName) AS MedianDisc  
FROM dbo.DimEmployee;  
  

Here is a partial result set.

DepartmentName        MedianCont    MedianDisc  
--------------------   ----------   ----------  
Document Control       16.826900    16.8269  
Engineering            34.375000    32.6923  
Human Resources        17.427850    16.5865  
Shipping and Receiving  9.250000     9.0000

See Also

PERCENTILE_CONT (Transact-SQL)