2nd highest salary sql

Here i have posted three methods to find second highest salary of an employee.



select max(salary) from employee where salary not in(select max(salary) from employee)


                                                                     OR



select max(salary) from employee where salary <=(select max(salary) from employee)




                                                                       OR

SELECT salary from(select salary from employee where rownum<=2 order by salary asc )  employee where rownum = 1;