How do you solve Second Highest Salary on LeetCode?

Second Highest Salary (LeetCode #176) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: Using subqueries can significantly reduce the number of comparisons needed.

What is the brute force solution for Second Highest Salary?

The brute force approach for Second Highest Salary is Brute Force, with O(n²) time complexity and O(1) space complexity. To find the second highest salary, we can compare each salary with every other salary. This is straightforward but inefficient, as it checks all possible pairs. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Second Highest Salary?

Second Highest Salary uses the following concepts: Database. The recommended patterns to study are: Subqueries, Aggregate Functions.

What are the interview tips for Second Highest Salary?

Always clarify edge cases, such as what to return if there is no second highest salary. Think about the efficiency of your solution and be prepared to explain why it's optimal. Practice writing SQL queries on paper or in a SQL environment to get comfortable with syntax.

What are common mistakes when solving Second Highest Salary?

Not considering the case where there is only one distinct salary. Forgetting to use DISTINCT if the same salary appears multiple times.

#176

Second Highest Salary

Medium

DatabaseSubqueriesAggregate Functions

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(1)

💡

Intuition

Time O(n)Space O(1)

Instead of comparing every salary, we can use a subquery to directly find the maximum salary that is less than the overall maximum salary, which is much more efficient.

⚙️

Algorithm

3 steps

1Step 1: Use a subquery to find the maximum salary from the Employee table.
2Step 2: In the outer query, find the maximum salary that is less than the result of the subquery.
3Step 3: If there is no such salary, the result will be null.

solution.py3 lines

1SELECT MAX(salary) AS SecondHighestSalary
2FROM Employee
3WHERE salary < (SELECT MAX(salary) FROM Employee);

ℹ

Complexity note: This complexity is linear because we only need to scan through the salaries twice: once for the maximum and once for the second maximum.

1Using subqueries can significantly reduce the number of comparisons needed.
2Understanding how to use aggregate functions like MAX() is crucial for efficient SQL queries.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.