How to get second highest salary department wise?

Question

Suppose we have some employees in each department.we have total 3 departments . Below is the sample source table named 'employee'

emp dept_id salary
A    10     1000
B    10     2000
C    10     3000
D    20     7000
E    20     9000
F    20     8000
G    30     17000
H    30     15000
I    30     30000
j    30     30000
k    30     17000

Here may same salary is exist in same department.

I use Wamp-server which has mysql-5.7.23

And I want to like:

B    10     2000
F    20     8000
G    30     17000

Answer 1

I think there are several way to solve the problem. Following solution from my side and works fine.

SELECT *
From employee e2 
WHERE e2.salary = (SELECT distinct salary FROM employee where dept_id=e2.dept_id order by salary desc limit 1,1);

I need only second highest salary value with department wise which is the input array of next operation in my project. Finally I use

SELECT e2.dept_id, max(e2.salary) From employee e2 WHERE e2.salary = (SELECT distinct salary FROM employee where dept_id=e2.dept_id order by salary desc limit 1,1) group by e2.dept_id