The use of JOINs as everyone knows is to get data from multiple tables. Exception JOIN is one kind of JOIN. The most powerful use is to get data that for not satisfied condition of JOINs. The below SQL describes on how to use Exception JOIN and the result how it retrieves.
SELECT LastName, Area FROM Employee EXCEPTION JOIN Department ON Employee.Dept = Department.Dept
Return list of employees only if they are NOT in a valid department
Employee ‘Smith’ is only one without a valid department.
EmployeeName Dept -------------- ------ Smith Null