Sql6 Completed

[HaswathaSridharan]

No description provided.

[super30admin]

1. Problem 1 (Game Play Analysis II):

   • Correctness: The solution correctly finds the first login date for each player and returns the corresponding device_id. This is a standard approach.
   • Time Complexity: O(n log n) for the groupby operation, which is efficient.
   • Space Complexity: O(n) for storing intermediate results.
   • Code Quality: The code is clean and readable. Could consider renaming 'df' to something more descriptive like 'first_logins'.

2. Problem 2 (Game Play Analysis III):

   • Correctness: The SQL query correctly calculates the running sum of games played per player. Window functions are the right approach here.
   • Time Complexity: O(n log n) for the window function operation.
   • Space Complexity: O(n) for the window frame.
   • Code Quality: Well-structured SQL query. Consider adding a comment explaining the window function for clarity.

3. Problem 3 (Shortest Distance in a Plane):

   • Correctness: The solution correctly finds the minimum distance between any two points. The join condition ensures each pair is only compared once.
   • Time Complexity: O(n²) due to the self-join, which is optimal for this problem.
   • Space Complexity: O(n²) for the join result.
   • Code Quality: Good SQL style. The join condition could be made more explicit with a comment.

4. Problem 4 (Combine Two Tables):

   • Correctness: Correctly performs a left join and returns the required columns. Handles missing addresses properly.
   • Time Complexity: O(n) for the merge operation.
   • Space Complexity: O(n) for the merged result.
   • Code Quality: Clean and efficient. Consider adding type hints for the return value.

5. Problem 5 (Customers with Strictly Increasing Purchases):

   • Correctness: The solution correctly identifies customers with strictly increasing yearly purchases. The CTE and join logic are appropriate.
   • Time Complexity: O(n²) for the self-join in the worst case.
   • Space Complexity: O(n) for the CTE.
   • Code Quality: Well-structured SQL. The HAVING clause logic could benefit from a brief comment explaining the count comparison.

General improvements:

• Adding comments to explain complex logic would improve maintainability.
• Consistent formatting (e.g., spaces around operators) would enhance readability.
• For SQL problems, consider adding EXPLAIN plans to discuss optimization opportunities.