SELECT DISTINCT a.deptno,dept.dname FROM 
(SELECT deptno,COUNT(empno) AS count_dpem FROM emp GROUP BY deptno) a INNER JOIN
(SELECT emp.deptno,e.count_empno/d.count_deptno AS avg_empno FROM 
(SELECT COUNT(deptno) AS count_deptno FROM dept) d,
(SELECT COUNT(empno) AS count_empno FROM emp) e,emp) b
ON a.deptno=b.deptno
INNER JOIN dept ON a.deptno=dept.deptno
WHERE a.count_dpem>b.avg_empno;

SELECT   deptno, dname
    FROM (SELECT e.deptno, d.dname,
                 COUNT (e.empno) OVER (PARTITION BY e.deptno) dcount,
                 COUNT (e.empno) OVER (PARTITION BY NULL) ecount,
                 COUNT (DISTINCT (d.deptno)) OVER (PARTITION BY NULL)
                                                                    deptcount
            FROM emp e, dept d
           WHERE e.deptno = d.deptno)
   WHERE dcount > (ecount / deptcount)
GROUP BY deptno, dname