Is operator in SQL SERVER

Is operator

Is operator is used to work with null values.

Write a query to get all the employees whose Commission is null
select * from employee1 where comm is null

Write a query to get all the employees whose Commission is not null
select * from employee1 where comm is not null

Write a Query to get the total salary of an employee(comm+sal)
select ename,sal+isnull(comm,0) as Total_sal from employee1

Null with any operation is Null

Thanks
Srinivas