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

Assuming Postgres,

Try This

select e1.* from emp e1  inner join (select avg(sal) avg_sal,dept_id from emp group by dept_id) as e2 on e1.dept_id=e2.dept_id and e1.sal>e2.avg_sal