Completed Sql6

[kaaviyavarrshini]

No description provided.

[super30admin]

1. Problem1_GamePlay2.sql:

   • Correctness: The solution correctly identifies the first login date for each player and returns the corresponding device_id. This is a standard approach using a subquery with MIN().
   • Time Complexity: O(n^2) due to the correlated subquery.
   • Space Complexity: O(n) for storing intermediate results.
   • Code Quality: The code is clean and readable. Consider using a JOIN with a derived table for potentially better performance.
   • Efficiency: Could be optimized with a window function (ROW_NUMBER()) instead of a subquery.

2. Problem2_GamePlay3.sql:

   • Correctness: Correctly calculates the running total of games played per player. This is a perfect use case for window functions.
   • Time Complexity: O(n log n) for the PARTITION BY and ORDER BY operations.
   • Space Complexity: O(n) for the window function computation.
   • Code Quality: Excellent use of window functions. Well-formatted and clear.
   • Efficiency: Already optimal for this problem.

3. Problem3_shortestDist.sql:

   • Correctness: Correctly finds the minimum distance between any two distinct points. The condition (p1.x!=p2.x or p1.y!=p2.y) properly excludes self-joins.
   • Time Complexity: O(n^2) due to the self-join.
   • Space Complexity: O(n^2) for the join result.
   • Code Quality: Clear and concise. The mathematical expression is correct.
   • Efficiency: This is the standard approach for this problem. No significant optimizations possible.

4. Problem4_Combine2Tables.sql:

   • Correctness: Correctly combines person and address tables with a LEFT JOIN to include all persons even without addresses.
   • Time Complexity: O(n) for the join operation.
   • Space Complexity: O(n) for the result set.
   • Code Quality: Simple and effective. Good use of LEFT JOIN.
   • Efficiency: Already optimal.

5. Problem5_CustomersWithIncreasingPurchase.sql:

   • Correctness: The logic appears correct for finding customers with strictly increasing yearly purchases, but the solution is somewhat complex.
   • Time Complexity: O(n^2) due to the self-join.
   • Space Complexity: O(n) for the CTE.
   • Code Quality: The solution could be simplified. The HAVING clause logic is clever but might be hard to maintain.
   • Efficiency: Could potentially be simplified with LAG() window function to compare consecutive years.

Overall, the student demonstrates good SQL skills with appropriate use of window functions and joins. The solutions are generally correct and efficient, with some opportunities for simplification in Problem5.