Completed Sql4

[alokusw2]

No description provided.

[super30admin]

1. Problem 1: The Number of Seniors and Juniors to Join the Company

   • Correctness: The solution correctly uses window functions to calculate cumulative salaries and then counts the number of seniors and juniors that can be hired within the budget. The approach is sound.
   • Time Complexity: O(n log n) due to the sorting in the window function.
   • Space Complexity: O(n) for storing the cumulative sums.
   • Code Quality: The code is well-structured and readable. The use of CTEs makes the logic clear.
   • Efficiency: The solution is efficient, but could be optimized by filtering candidates by experience before calculating cumulative sums.

2. Problem 2: League Statistics

   • Correctness: The solution correctly calculates the statistics for each team, including points, goals, and goal difference. The UNION ALL approach to combine home and away matches is effective.
   • Time Complexity: O(n) for processing all matches.
   • Space Complexity: O(n) for storing intermediate results.
   • Code Quality: The code is clean and easy to understand. The use of subqueries and JOIN is appropriate.
   • Efficiency: The solution is efficient, but could be optimized by avoiding the subquery and using a single pass over the matches table.

3. Problem 3: Sales Person

   • Correctness: The solution correctly identifies salespersons who did not have any orders related to the company "RED". The NOT IN clause is appropriate here.
   • Time Complexity: O(n) for the subquery and O(m) for the main query.
   • Space Complexity: O(n) for storing the subquery results.
   • Code Quality: The code is simple and straightforward. The use of NOT IN is clear.
   • Efficiency: The solution is efficient, but could be optimized by using NOT EXISTS instead of NOT IN for better performance in some databases.

4. Problem 4: Friend Requests II

   • Correctness: The solution correctly identifies the person with the most friends by combining requester and accepter IDs and counting occurrences.
   • Time Complexity: O(n) for processing all friend requests.
   • Space Complexity: O(n) for storing the combined IDs.
   • Code Quality: The code is concise and easy to understand. The use of CTEs is appropriate.
   • Efficiency: The solution is efficient, but could be optimized by using a more direct approach without UNION ALL if possible.

Overall, the student's solutions are correct, efficient, and well-structured. The code quality is high, and the solutions follow best practices. Minor optimizations could be made, but they are not necessary for correctness.