Completed Mock_SQL

[RISHIKA29]

No description provided.

[super30admin]

1. Correctness:

   • Mock 1.sql: The solution correctly calculates the total distance traveled by each user and handles NULL values with IFNULL. The LEFT JOIN ensures all users are included, even those without rides.
   • Mock 2.sql: The solution correctly calculates the difference between apples and oranges sold per date using a CASE statement and aggregation.

2. Time Complexity:

   • Mock 1.sql: The query involves a window function (SUM OVER PARTITION) which is O(n) where n is the number of rows in Rides. The LEFT JOIN is O(m + n) where m is the number of users.
   • Mock 2.sql: The query involves a GROUP BY operation which is O(n) where n is the number of rows in Sales.

3. Space Complexity:

   • Mock 1.sql: The CTE stores intermediate results, requiring O(n) space where n is the number of rides.
   • Mock 2.sql: The CTE stores intermediate results, requiring O(n) space where n is the number of sales records.

4. Code Quality:

   • Both solutions are well-structured and readable.
   • The use of CTEs improves readability and modularity.
   • Consistent indentation and formatting.
   • The CASE statement in Mock 2.sql is clear and effective.

5. Efficiency:

   • Mock 1.sql: The DISTINCT keyword might be unnecessary if the CTE already ensures unique user_id entries. Removing it could improve performance.
   • Mock 2.sql: The solution is already efficient, but adding a comment explaining the CASE logic could improve maintainability.

[super30admin]

Let me evaluate each solution separately:

Mock_SQL 1:

1. Correctness: The solution correctly calculates the total distance traveled by each user and handles NULL values appropriately with IFNULL. The LEFT JOIN ensures all users are included.
2. Time Complexity: O(n log n) due to the window function and sorting.
3. Space Complexity: O(n) for storing the CTE results.
4. Code Quality: The code is well-structured and readable. Good use of CTE and DISTINCT to avoid duplicates.
5. Efficiency: The solution is efficient. One minor improvement could be to use SUM directly in the GROUP BY instead of window function for better clarity.

Mock_SQL 2:

1. Correctness: The solution correctly calculates the difference between apples and oranges sold per date using CASE and SUM.
2. Time Complexity: O(n) for the GROUP BY operation.
3. Space Complexity: O(n) for storing the CTE results.
4. Code Quality: The code is clean and easy to understand. Good use of CASE statement.
5. Efficiency: The solution is optimal. No significant improvements needed.

General strengths:

• Both solutions use CTEs effectively to organize complex logic
• Proper handling of edge cases (NULL values in solution 1)
• Clear and consistent formatting
• Appropriate use of SQL functions and clauses

Areas for improvement:

• In solution 1, consider adding comments to explain the purpose of the CTE
• The ORDER BY in solution 1 references CTE.travelled_distance which could be NULL, though it works due to SQL's NULL handling
• Consider using COALESCE instead of IFNULL for better portability (though this is minor)