Oracle CUME_DIST

Summary: in this tutorial, you will learn how to calculate a cumulative distribution of a value in a set of values by using the Oracle CUME_DIST() function.

Introduction to Oracle CUME_DIST() function

Sometimes, you want to pull the top or bottom x% values from a data set e.g., top 5% salesman by volume. To do this, you can use the Oracle CUME_DIST() function.

The CUME_DIST() function is an analytic function that calculates the cumulative distribution of a value in a set of values. The result of CUME_DIST() is greater than 0 and less than or equal to 1. Tie values evaluate to the same cumulative distribution value.

The following shows the syntax of the Oracle CUME_DIST() function:

CUME_DIST() OVER (
    [ query_partition_clause ] 
    order_by_clause
)

Because CUME_DIST() function is order sensitive, the order_by_clause is required. The order_by_clause has the following syntax:

ORDER BY expression1 
            [ASC | DESC ]  
            [NULLS FIRST | LAST] 
        [, expression2 
            [ASC | DESC ] 
            [NULLS FIRST | LAST],... ]

The ORDER BY clause specifies the order of rows in each partition.

The query_partition_clause has the following form:

PARTITION BY expression1 [,expression2,..]

The PARTITION BY clause divides the result set into multiple partitions. It is optional. Omitting this clause means that the function will treat the whole result set as a single partition.

Oracle CUME_DIST() examples

Using Oracle CUME_DIST() function over the result set example

The following statement calculates the sales percentile for each salesman in 2017:

SELECT 
    salesman_id,
    sales,  
    ROUND(cume_dist() OVER (ORDER BY sales DESC) * 100,2) || '%' cume_dist
FROM 
    salesman_performance
WHERE 
    YEAR = 2017;

Here is the result:

As shown in the output, 33.33 % of salesman have sales amount greater than 1.99 million.

Using Oracle CUME_DIST() function over the partition example

The following statement calculates the sales percentile for each salesman in 2016 and 2017.

SELECT 
    salesman_id,
    year,
    sales,  
    ROUND(CUME_DIST() OVER (
        PARTITION BY year
        ORDER BY sales DESC
    ) * 100,2) || '%' cume_dist
FROM 
    salesman_performance
WHERE 
    year in (2016,2017);   

Here is the output:

In this example:

• The PARTITION BYclause divided the result set into two partitions by year, 2016 and 2017.
• The ORDER BY clause sorted rows in each partition by sales amount in descending order to which the CUME_DIST() function is applied.

To get top 30% of the salesman by sales revenue in 2016 and 2017, you use the following query:

WITH cte_sales AS (
SELECT 
    salesman_id,
    year,
    sales,  
    ROUND(CUME_DIST() OVER (
        PARTITION BY year
        ORDER BY sales DESC
    ),2) cume_dist
FROM 
    salesman_performance
WHERE 
    year in (2016,2017)
)  
SELECT 
  * 
FROM 
    cte_sales
WHERE 
    cume_dist <= 0.30;

The output is:

In this tutorial, you have learned how to use the Oracle CUME_DIST() function to calculate the cumulative distribution of a value in a set of values.