Interview Question: What is the Query to Find Second Highest Salary of Employee?
Query to find Second highest salary of employee is one of the most commonly asked question in SQL interviews:
select distinct salary from Empoyee e1 where 2 = (select count(distinct salary) from Employee e2 where e1.salary <= e2.salary);
- Explaination of Query:
1.Distinct keyword:–>The Distinct keyword is very useful keyword which will eliminate duplicates and fetches the Result.
2.Aliases–> Alias is nothing but the obfuscation technique to protect the real names of database fields
3.Count()–>Count() function is used to count the records in the table.
Step 1: So to understand the above query we will start with simple select statement.
Select * from Employee;
Here our intention is to fetch the record where salary is second highest.
Step 2 :We will fetch the distinct Salary of employee and give the alias to it.
Select distinct Salary from Employee e1;
Step 3 :We need to calculate Second highest salary.So we need to get the count of all distinct salaries.
Select count(distinct Salary) from Employee e2;
Step 4 :We actually need to calculate second highest salary.So we will modify the Step 2 query and Step3 Query:
Select distinct Salary from Employee e1 where 2=
Select count(distinct Salary) from Employee e2 where e1.salary<=e2.salary;
The above query will give us the second highest salary of employee.Hope you will understand the logic behind fetching the second highest salary.There are other ways to find second highest salary of employee using rank and dense_rank function.
Other ways to find second highest salary:
SELECT max(e1.sal), e1.deptno FROM s_emp e1 WHERE sal < (SELECT max(sal) FROM s_emp e2 WHERE e2.deptno = e1.deptno) GROUP BY e1.deptno;
SELECT * FROM (SELECT S.*,DENSE_RANK() OVER (PARTITION BY DNO ORDER BY SALARY DESC) DR FROM SOURCE ) S WHERE S.DR=2;
SELECT Name FROM Employees WHERE Salary = ( SELECT DISTINCT TOP (1) Salary FROM Employees WHERE Salary NOT IN (SELECT DISTINCT TOP (1) Salary FROM Employees ORDER BY Salary DESCENDING) ORDER BY Salary DESCENDING);
There are some other ways of calculating the second highest salary in different DBMS i.e. Oracle,Mysql,Postgresql:
Type 1 : Using correlated subquery:
SELECT name, salary FROM Employee e1 WHERE N-1 = (SELECT COUNT(DISTINCT salary) FROM Employee e2 WHERE e2.salary > e1.salary)SELECT name, salary FROM Employee e1 WHERE 2-1 = (SELECT COUNT(DISTINCT salary) FROM #Employee e2 WHERE e2.salary > e1.salary); Using this method of finding out the second highest salary is slow because of the execution of inner query again and again.
Type 2: Microsoft SQL Server (Using Top Function)
SELECT TOP 1 salary FROM ( SELECT DISTINCT TOP N salary FROM Employee ORDER BY salary DESC ) AS temp ORDER BY salary;
Type3 : Mysql (using limit Clause)
SELECT salary FROM Employee ORDER BY salary DESC LIMIT 1,1;
Type 4: Oracle Function (using rownum function)
SELECT Salary FROM ( SELECT e.Salary, ROW_NUMBER() OVER (ORDER BY salary DESC) rn FROM Employee e ) WHERE rn = 2;
Type 5 : One of the website reader has suggested this solution Solution of Gautam Roy :
select * from OrderDetails a where a.Quantity < (select max(b.Quantity) from OrderDetails b) order by a.Quantity DESC limit 1;
These are above methods to calculate 2nd highest salary of Employee.If you like this article then don't forget to share it.