select * from emp
 where n-1 = (select count(*) from emp e 
 where emp.salary<e.salary)

in place of n-1 you can keep zero for first hight salary 
and 1 for second hightest salary.....etc

select salary from tablename order by salary desc limit 1,1;

Select * from emp where sal=(select Max(sal) from emp where 
sal<(select Max(Sal) from emp)

select top 1 a.salary,* from emp a
where a.salary not in(select top (n-1) b.salary from emp b)

here n is the Nth values:if you want secong highest: keep n 
as 2 so the query will become

select top 1 a.salary,* from emp a
where a.salary not in(select top 1 b.salary from emp b)