MySQL query to find the second highest salary

Second maximum salary using sub query and IN clause:

SELECT MAX(salary) FROM employees WHERE salary NOT IN ( SELECT Max(salary) FROM employees);

Second maximum salary using sub query and < operator instead of IN clause:

SELECT MAX(salary) From employees WHERE salary < ( SELECT Max(salary) FROM employees);

Second maximum salary using the LIMIT clause in query:

SELECT salary FROM (SELECT salary FROM employees ORDER BY salary DESC LIMIT 2) AS Emp ORDER BY salary LIMIT 1;