how to use NULLS FIRST function in oracle database query

The NULLS FIRST Function in Oracle SQL / PLSQL is used to place the NULL records at the beginning in the fetched records.

Syntax for using the NULLS FIRST function in Oracle SQL / PLSQL is ;
SELECT column(s)
ROW_NUMBER() OVER (ORDER BY column NULLS FIRST)
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
107	Emp G	12000	Sales	10
108	Emp H	12000	Sales

Now, suppose we want to see the employee_name and commission and also want that the employees having no commission should be listed first then we can achieve the same using NULLS FIRST function as:

SELECT employee_name
       ,commission
       ,ROW_NUMBER () OVER (ORDER BY commission NULLS FIRST) SNO
FROM employee;

We will get the following result:

Employee_Name	Commission	SNO
Emp D		1
Emp H		2
Emp G	10	3
Emp E	10	4
Emp F	10	5
Emp A	10	6
Emp C	20	7
Emp B	20	8

Here we can see that we have successfully fetched employees having no commission first in the list.