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

Answer 2

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

Answer 3

please try with below query

Select * from employee a where Employee_Salary > (select avg(Employee_Salary) from 
employee b group by Department_ID having b.Department_ID = a.Department_ID)

or

Select * from employee a where Employee_Salary> (select avg(Employee_Salary) from 
employee b where b.Department_ID = a.Department_ID group by Department_ID)

Answer 4

Try This... This not tested.

SELECT * from employee join (SELECT AVG(employee_salary) as sal, department_ID 
FROM employee GROUP BY Department_ID) as t1 
ON employee.department_ID = t1.department_ID 
where employee.employee_salary > t1.sal

Answer 5

you can try this way as well !

  select FirstName,E.DepartmentName,BaseRate,EB.avgSAL
  From DimEmployee E
  inner join
  (select avg(BaseRate) As avgSAL,DepartmentName
  from DimEmployee
  group by DepartmentName ) EB
  ON E.DepartmentName = Eb.DepartmentName
  where E.BaseRate > Eb.avgSAL

Answer 6

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