Highest Salary by Dept
SELECT DEPTNO, max(SAL) as MaxSalary FROM EmpSal
group BY DEPTNO
Second Best Salary by Dept
SELECT es.DEPTNO,max(es.SAL) as SecondBest FROM
(
SELECT DEPTNO, max(SAL) as MaxSalary FROM EmpSal
group BY DEPTNO) P
JOIN EmpSal es ON P.DEPTNO= es.DEPTNO
WHERE es.SAL!= P.MaxSalary
GROUP BY es.DEPTNO