Write a SQL query to find the second maximum element from a table.

Both options you find max as a subset and then exclude from main select
sql> SELECT MAX( col ) FROM table
 	WHERE col < ( SELECT MAX( col ) FROM table);
sql> SELECT MAX(col) FROM table 
WHERE col NOT IN (SELECT MAX(col) FROM table);

SELECT name, MAX(salary) AS salary
  FROM employee
 WHERE salary < (SELECT MAX(salary)
                 FROM employee); 

/*  Highest salary by Department/Location   */
SELECT e.ename, e.sal, e.deptno, d.loc
FROM emp e
JOIN dept d
ON e.deptno = d.deptno
WHERE e.sal in
( 	
  	select max(sal) 
  	from emp 
  	group by deptno
)