SELECT every employee that has a higher salary than the AVERAGE of his department

Question

I have only 1 table named EMPLOYEE on my database with the 3 following collumns:

Employee_Name, Employee_Salary, Department_ID

Answer 1

Try this without GROUP BY

SELECT * FROM employee  E1 
WHERE [Employee_Salary] > (
                            SELECT AVG([Employee_Salary]) FROM employee  E2 
                            WHERE E2.[Department_ID] = E1.[Department_ID]
                           )

SQL FIDDLE DEMO