Is Second Highest Salary II easy or hard?

Second Highest Salary II is generally considered a medium-level SQL problem. The challenge comes from handling duplicate salaries correctly and returning NULL when a second highest value does not exist. Understanding window functions like DENSE_RANK() makes the solution straightforward.

Second Highest Salary II Python/Java solution

For SQL problems like this, the implementation is written as a database query rather than Python or Java code. In data processing workflows, a similar approach can be implemented in pandas using rank or sorting operations. The same idea applies: rank salaries descending and select the second distinct value.

How to solve Second Highest Salary II in O(n)?

Pure O(n) solutions are uncommon in SQL because ranking typically requires sorting. Some theoretical approaches using aggregates like MAX(salary) with a conditional filter (salary < max_salary) can reduce work but still depend on scans and optimizer behavior. In practice, databases implement these queries with sorting, giving O(n log n) performance.

What is the best approach for Second Highest Salary II?

The most reliable solution uses the SQL window function DENSE_RANK() ordered by salary in descending order. Assign ranks to each distinct salary and filter for rank = 2. This approach handles duplicate salaries naturally and keeps the query easy to extend. Time complexity is O(n log n) due to sorting.

Is Second Highest Salary II asked at Google/Amazon/Meta?

Variants of the 'second highest value' query are common in SQL interviews at companies like Amazon, Google, and Meta. Interviewers use it to test understanding of ranking functions, DISTINCT handling, and subqueries. The window function solution using DENSE_RANK() is often the expected answer.

What data structure is used in Second Highest Salary II?

The problem relies on relational database operations rather than traditional data structures. Internally, the database engine performs sorting and ranking operations. Window functions such as DENSE_RANK() conceptually assign ordered ranks to rows based on salary values.

What is the time complexity of Second Highest Salary II?

Most SQL solutions require sorting salaries in descending order, which results in O(n log n) time complexity. Window function approaches like DENSE_RANK() and subqueries using ORDER BY both rely on sorting. Space complexity is typically O(n) for window functions and O(1) extra space for simpler subqueries.

3338. Second Highest Salary II - Practice Online

Q: What is the best approach for Second Highest Salary II?

The most reliable solution uses the SQL window function DENSE_RANK() ordered by salary in descending order. Assign ranks to each distinct salary and filter for rank = 2. This approach handles duplicate salaries naturally and keeps the query easy to extend. Time complexity is O(n log n) due to sorting.

Q: Is Second Highest Salary II asked at Google/Amazon/Meta?

Variants of the 'second highest value' query are common in SQL interviews at companies like Amazon, Google, and Meta. Interviewers use it to test understanding of ranking functions, DISTINCT handling, and subqueries. The window function solution using DENSE_RANK() is often the expected answer.

Q: What data structure is used in Second Highest Salary II?

The problem relies on relational database operations rather than traditional data structures. Internally, the database engine performs sorting and ranking operations. Window functions such as DENSE_RANK() conceptually assign ordered ranks to rows based on salary values.

Q: What is the time complexity of Second Highest Salary II?

Most SQL solutions require sorting salaries in descending order, which results in O(n log n) time complexity. Window function approaches like DENSE_RANK() and subqueries using ORDER BY both rely on sorting. Space complexity is typically O(n) for window functions and O(1) extra space for simpler subqueries.

Table: employees

+------------------+---------+
| Column Name      | Type    |
+------------------+---------+
| emp_id           | int     |
| salary           | int     |
| dept             | varchar |
+------------------+---------+
emp_id is the unique key for this table.
Each row of this table contains information about an employee including their ID, salary, and department.

Write a solution to find the employees who earn the second-highest salary in each department. If multiple employees have the second-highest salary, include all employees with that salary.

Return the result table ordered by emp_id in ascending order.

The result format is in the following example.

Example:

Input:

employees table:

+--------+--------+-----------+
| emp_id | salary | dept      |
+--------+--------+-----------+
| 1      | 70000  | Sales     |
| 2      | 80000  | Sales     |
| 3      | 80000  | Sales     |
| 4      | 90000  | Sales     |
| 5      | 55000  | IT        |
| 6      | 65000  | IT        |
| 7      | 65000  | IT        |
| 8      | 50000  | Marketing |
| 9      | 55000  | Marketing |
| 10     | 55000  | HR        |
+--------+--------+-----------+

Output:

+--------+-----------+
| emp_id | dept      |
+--------+-----------+
| 2      | Sales     |
| 3      | Sales     |
| 5      | IT        |
| 8      | Marketing |
+--------+-----------+

Explanation:

Sales Department:
- Highest salary is 90000 (emp_id: 4)
- Second-highest salary is 80000 (emp_id: 2, 3)
- Both employees with salary 80000 are included
IT Department:
- Highest salary is 65000 (emp_id: 6, 7)
- Second-highest salary is 55000 (emp_id: 5)
- Only emp_id 5 is included as they have the second-highest salary
Marketing Department:
- Highest salary is 55000 (emp_id: 9)
- Second-highest salary is 50000 (emp_id: 8)
- Employee 8 is included
HR Department:
- Only has one employee
- Not included in the result as it has fewer than 2 employees