PERCENT_RANK Function in Oracle SQL

Oracle SQL / PLSQL PERCENT_RANK function is used to calculate the rank of a hypothetical row.

As an aggregate function a rank is calculated as r minus 1 divided by the number of rows in the aggregate group.
As an analytical function rank is calculated as r minus 1 divided by the number of rows in the aggregate group minus 1.
A Percent_Rank returns a value between 0 and 1 inclusive.

The SQL PERCENT_RANK function can be used in as an Aggregate and Analytical Function.

Oracle SQL / PLSQL PERCENT_RANK Function Syntax as an Aggregate Function is:

SELECT PERCENT_RANK(expression1, expression2 . . , expressionN)
WITHIN GROUP (ORDER BY column1, column2, . . , columnN)
FROM table_name;

Oracle SQL / PLSQL PERCENT_RANK Function Syntax as an Analytical Function is:

SELECT PERCENT_RANK() OVER ([PARTITION BY column(s)] ORDER BY column(s))
FROM table_name;

Example 1: Using Oracle SQL / PLSQL PERCENT_RANK Function as AGGREGATE function

Suppose we have a table named ‘employee’ as shown below:

Employee_Id	Employee_Name	Salary	Department	Commission
101	Emp A	10000	Sales	10
102	Emp B	20000	IT	20
103	Emp C	28000	IT	20
104	Emp D	30000	Support
105	Emp E	32000	Sales	10
106	Emp F	40000	Sales	10

If we write our query Oracle SQL PERCENT_RANK Function with SELECT Statement as:

SELECT PERCENT_RANK(15000) WITHIN GROUP (ORDER BY salary)
FROM employee;

We will get ‘0.166666666666667’ as the PERCENT_RANK of 15000 because as per the data in the ‘employee’ table if we sort the ‘salary’ column from lowest to highest salary then 15000 will come at the 2^nd position in that list and the total number of rows will be 6.

Hence the percent_rank for 15000 is calculated as:

(Position of the row-1/total rows) i.e. (2-1/6) = 1/6 = 0.166666666666667

Example 2: Using Oracle SQL / PLSQL PERCENT_RANK Function as ANALYTICAL function

As mentioned earlier, the syntax for the Oracle SQL PERCENT_RANK function as an Analytical Function is:

SELECT PERCENT_RANK() OVER ([PARTITION BY column(s)] ORDER BY column(s))
FROM table_name;

Suppose we have a table named ‘employee’ as shown below:

Employee_Id	Employee_Name	Salary	Department	Commission
101	Emp A	10000	Sales	10
102	Emp B	20000	IT	20
103	Emp C	28000	IT	20
104	Emp D	30000	Support
105	Emp E	32000	Sales	10
106	Emp F	40000	Sales	10

If we write our query Oracle SQL PERCENT_RANK Function with SELECT Statement as:

SELECT employee_name
       ,salary
       ,department
       ,PERCENT_RANK() OVER (PARTITION BY department ORDER BY salary) Percent_Ranking
FROM employee;

We will get the following output:

Employee_Name	Salary	Department	Percent_Ranking
Emp B	20000	IT	0
Emp C	28000	IT	1
Emp A	10000	Sales	0
Emp E	32000	Sales	0.5
Emp F	40000	Sales	1
Emp D	30000	Support	0

Here we can see that Oracle SQL PERCENT_RANK function is being used as an analytical function.

It returns the position or rank of records in group of records partitioned by a criteria e.g. in our case we have partitioned the records by ‘department’ and then within that partition we are ranking the records relative to each other.

First row is always given a percent rank of ‘0’ by Oracle SQL PERCENT_RANK Function.

The PERCENT_RANK is this case is calculated as:

(Position Of the rows-1/total rows -1)

e.g. for Emp E percent rank is calculated using

(Position Of the rows-1/total rows -1) as (2-1/3-1) = (1/2) = 0.5

And for Emp F percent rank is calculated using

(Position Of the rows-1/total rows -1) as (3-1/3-1) = 2/2 = 1