How to find second highest or maximum salary of Employee in SQL - Interview question

Employee is one of the most frequently asked SQL interview question similar to finding duplicate records in table and when to use truncate vs delete. There are many ways to find second highest salary based upon which database you are using as different database provides different feature which can be used to find second maximum or Nth maximum salary of employee. Well this question can also be generalized with other scenario like finding second maximum age etc. In this SQL tutorial we will see different example of SELECT SQL query to find second highest salary independent of databases or you may call in ANSI SQL and other SQL queries which uses database specific feature to find second maximum salary.

SQL query to find second maximum salary of Employee

In this section we will write SQL query to get second highest salary of Employee. Before writing query its good to be familiar with schema as well as data in table. Here is the Employee table we will be using this SQL example:

mysql > SELECT * FROM Employee;
+ --------+----------+---------+--------+
| emp_id | emp_name | dept_id | salary |
+ --------+----------+---------+--------+
| 1 | James | 10 | 2000 |
| 2 | Jack | 10 | 4000 |
| 3 | Henry | 11 | 6000 |
| 4 | Tom | 11 | 8000 |
+ --------+----------+---------+--------+
4 rows INSET ( 0.00 sec )

If you look data, you will find that second maximum salary in this case is 6000 and employee name is Henry. Now let’s see some SQL example to find out this second maximum salary.

Second maximum salary using sub query and IN clause

Sub queries in SQL are great tool for this kind of scenario, here we first select maximum salary and then another maximum excluding result of subquery. To learn more about Subquery see correlate and non-correlate subquery in SQL

mysql > SELECT max (salary ) FROM Employee WHERE salary NOT IN ( SELECT max (salary ) FROM Employee );
+ -------------+
| max (salary ) |
+ -------------+
| 6000 |
+ -------------+
1 row INSET ( 0.00 sec )

Here is another SQL query to find second highest salary using subquery and < operator instead of IN clause:

mysql > SELECT max (salary ) FROM Employee WHERE salary < ( SELECT max (salary ) FROM Employee );
+ -------------+
| max (salary ) |
+ -------------+
| 6000 |
+ -------------+
1 row INSET ( 0.00 sec )

Both of above SQL example will work on all database including Oracle, MySQL, Sybase and SQL Server as they are written using standard SQL keywords. But sometime you can also use database specific features like TOP keyword of SQL Server or Sybase database to find out second highest salary of Employee.

Second highest salary using TOP keyword of Sybase or SQL Server database

TOP keyword of Sybase and SQL Server database is used to select top record or row of any result set, by carefully using TOP keyword you can find out second maximum or Nth maximum salary as shown below.

SELECT TOP 1 salary FROM ( SELECT TOP 2 salary FROM employees ORDER BY salary DESC ) AS emp ORDERBY salary ASC

Here is what this SQL query is doing : First find out top 2 salary from Employee table and list them in descending order, Now second highest salary of employee is at top so just take that value. Though you need to keep in mind of using distinct keyword if there are more than one employee with top salary, because in that case same salary will be repeated and TOP 2 may list same salary twice.

Second maximum salary using LIMIT keyword of MYSQL database

LIMIT keyword of MySQL database is little bit similar with TOP keyword of SQL Server database and allows to take only certain rows from result set. If you look at below SQL example, its very much similar to SQL Server TOP keyword example.

mysql > SELECT salary FROM ( SELECT salary FROM Employee ORDERBY salary DESCLIMIT 2 ) AS emp ORDERBY salary LIMIT 1;
+ --------+
| salary |
+ --------+
| 6000 |
+ --------+
1 row INSET ( 0.00 sec )

That’s on How to find second highest salary of Employee using SQL query. This is good question which really test your SQL knowledge, its not tough but definitely tricky for beginners. As follow up question you can ask him to find third maximum salary or Nth maximum salary as well.

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Read more: http://javarevisited.blogspot.com/2012/12/how-to-find-second-highest-or-maximum-salary-sql.html#ixzz2khph0MQr