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 using EXISTS() like:

SELECT t1.Employee_Name, t1.Employee_Salary, t1.Department_ID
FROM Employee t1
WHERE EXISTS
(
 SELECT t2.Department_ID, AVG(t2.Employee_Salary) as AvgSalary
 FROM Employee t2
 WHERE   t1.Department_ID = t2.Department_ID
 GROUP BY t2.Department_ID
 HAVING t1.Employee_Salary>AVG(t2.Employee_Salary)

);

See Fiddle Demo