second max salary in sql

SELECT MAX(SALARY)
FROM EMPLOYEES
WHERE SALARY != (SELECT MAX(SALARY) FROM EMPLOYEES);

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);

/* sql 2nd highest salary employee */
select sal, ename
from emp
where sal =
    (
        select max(sal) from emp where sal <
            (select max(sal) from emp)
    )
----------------------------------------------- option 2
select *
from 
(
    select ename, sal, dense_rank() over(order by sal desc) rank
    from emp
)
where rank =2;

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