This question mostly ask at the time of interview from the candidates who are freshers or 1 year experience. Even this question asked from me may times when i was comer in web development field.
So i am going to show you some possible ways to find 2nd or nth highest salary.
For Exp: Employee Table(ET)
| EID | EmployeeName | Salary |
|---|---|---|
| 1 | Employee-1 | 20,000 |
| 2 | Employee-2 | 22,000 |
| 3 | Employee-3 | 21,000 |
| 4 | Employee-4 | 19,000 |
| 5 | Employee-5 | 21,000 |
1:- How to find nth highest salary no condition
In this case you can use very basic limit and max methods of sql
SELECT DISTINCT(Salary) FROM ET ORDER BY Salary DESC LIMIT n-1,1
Where n is the position you are looking for
If n= 2 query will become
SELECT DISTINCT(state_id) FROM crm_cities ORDER BY state_id DESC LIMIT 1,1
Output will be: 21,000
2:- How to find all nth highest salary where the condition is you have to find all 2nd highest paid employees.
In this case you can use sub query feature of sql.
SELECT Salary FROM ET WHERE Salary = (SELECT DISTINCT(Salary) FROM ET ORDER BY Salary DESC LIMIT n-1,1)
Where n is the position you are looking for
If n= 2 query will become
SELECT Salary FROM ET WHERE Salary = (SELECT DISTINCT(Salary) FROM ET ORDER BY Salary DESC LIMIT 1,1)
Output will be: 21,000 , 21,000
3:- How to find 2nd highest salary without using LIMIT conditions.
In this case you can use NOT IN conditions in sql
SELECT MAX(Salary) FROM ET WHERE Salary NOT IN (SELECT MAX(Salary) FROM ET)
Output will be: 21,000
4:- How to find 2nd highest salary without using LIMIT and Sub-Query
In this case you can use self-join method
SELECT MAX( E1.Salary ) FROM ET E1, ET E2 WHERE E1.Salary < E2.Salary Output will be: 21,000
Hope this will help you to find the right answer as your need.. 
