2nd highest salary of an employee?

MySQL:
Sub queries in SQL are great tool for this kind of scenario, here we first select maximum salary and then another maximum excluding result of subquery
mysql> SELECT max(salary) FROM Employee WHERE salary NOT IN (SELECT max(salary) FROM Employee);
using subquery and < operator instead of IN clause:
mysql> SELECT max(salary) FROM Employee WHERE salary < (SELECT max(salary) FROM Employee);
Oracle:
using ROW_NUMBER
select * from ( select e.*, row_number() over (order by salary desc) as row_num from Employee e ) where row_num = 2;
Using DENSE_RANK():
SELECT * FROM (SELECT S.*,DENSE_RANK() OVER (PARTITION BY DNO ORDER BY SALARY DESC) DR FROM SOURCE ) S WHERE S.DR=2;