Completed SQL3

[alokusw2]

No description provided.

[super30admin]

1. Correctness:

   • Problem 1 (Consecutive Numbers): The solution correctly identifies numbers appearing at least three times consecutively by joining the table to itself and checking for consecutive IDs and matching numbers.
   • Problem 2 (Number of Passengers in Each Bus): The solution uses a window function to count passengers arriving before each bus and then calculates the difference between consecutive buses. This appears correct.
   • Problem 3 (User Activity): The solution correctly counts distinct users active within the 30-day window.
   • Problem 4 (Dynamic Pivoting): The dynamic SQL approach is correct for pivoting the table by store.

2. Time Complexity:

   • Problem 1: O(n) due to the self-joins on indexed IDs.
   • Problem 2: O(n log n) due to the window function and sorting.
   • Problem 3: O(n) for scanning the Activity table.
   • Problem 4: O(n) for building the pivot, but depends on the number of stores.

3. Space Complexity:

   • Problem 1: O(n) for storing the intermediate joined results.
   • Problem 2: O(n) for the window function results.
   • Problem 3: O(n) for storing the grouped results.
   • Problem 4: O(n) for the dynamic SQL execution.

4. Code Quality:

   • The solutions are well-structured and readable.
   • SQL formatting is consistent.
   • Comments are present where needed, especially in the dynamic pivoting solution.
   • Best practices are followed, such as using DISTINCT where appropriate and proper JOIN conditions.

5. Efficiency:

   • All solutions appear efficient for their respective problems.
   • No obvious optimizations are needed, though for Problem 1, an alternative approach using window functions could be considered for potentially better performance with large datasets.