Leetcode Problem 176. Second Highest Salary

SQL Algorithm

1. Use a sub-query to select distinct salaries from the Employee table.
2. Order the result in descending order.
3. Apply LIMIT 1 OFFSET 1 to get the second highest salary.
4. Use IFNULL to handle the case where there is no second highest salary, returning NULL in such a case.

Pandas Algorithm

1. Drop duplicate salaries from the employee DataFrame to ensure uniqueness.
2. Sort the DataFrame by salary in descending order.
3. Check if there are at least two unique salaries.
4. If so, select the second highest salary; otherwise, return None to indicate the absence of a second highest salary.