Completed MockSQL2

[alokusw2]

No description provided.

[super30admin]

1. Correctness:

   • For Problem 1, the solution correctly identifies customers who bought all products by using a nested NOT EXISTS approach. This is a standard way to solve the "division" problem in SQL.
   • For Problem 2, the solution is incorrect. It calculates total sales per product but doesn't address the requirement to find sales in the first year each product was sold.

2. Time Complexity:

   • Problem 1's solution has a time complexity of approximately O(n³) due to the nested NOT EXISTS clauses, which could be inefficient for large datasets.
   • Problem 2's solution has a time complexity of O(n) for the GROUP BY operation, but it doesn't solve the actual problem.

3. Space Complexity:

   • Both solutions have space complexity of O(n) as they need to store intermediate results.

4. Code Quality:

   • The SQL is syntactically correct and formatted clearly.
   • The solution for Problem 1 shows good understanding of SQL logic.
   • Problem 2's solution doesn't match the problem requirements, indicating a need for better problem understanding.

5. Efficiency:

   • For Problem 1, an alternative approach using COUNT DISTINCT might be more efficient:

     SELECT customer_id
     FROM Sales
     GROUP BY customer_id
     HAVING COUNT(DISTINCT product_id) = (SELECT COUNT(*) FROM Product)
     

   • For Problem 2, the student needs to first find the minimum year per product, then join back to get all sales in those years.

Areas for Improvement:

• Carefully read and understand all problem requirements before implementing solutions.
• Consider alternative approaches that might be more efficient for large datasets.
• For Problem 2, the solution should first identify the first year for each product, then filter sales accordingly.

[super30admin]

1. Correctness:

   • For Problem 1, the solution appears to correctly identify customers who bought all products by using a nested NOT EXISTS approach. This is a standard way to solve "division" problems in SQL.
   • For Problem 2, the solution is incorrect. It simply groups by product_id and sums quantities, which doesn't address the requirement to find sales in the first year each product was sold.

2. Time Complexity:

   • Problem 1's solution has a time complexity of approximately O(n³) due to the nested NOT EXISTS clauses, which could be inefficient for large datasets.
   • Problem 2's solution has a time complexity of O(n) for the GROUP BY operation, but it doesn't solve the actual problem.

3. Space Complexity:

   • Both solutions have space complexity proportional to their result sets, which is reasonable.

4. Code Quality:

   • The SQL is syntactically correct and formatted clearly.
   • Problem 2's solution shows a lack of understanding of the requirements.
   • Missing proper indentation in the nested queries for Problem 1.

5. Efficiency:

   • Problem 1 could potentially be optimized by using COUNT DISTINCT with GROUP BY and HAVING instead of nested NOT EXISTS.
   • Problem 2 needs a complete rework to find the first year each product was sold and then filter sales accordingly.

Areas for Improvement:

• Problem 2 needs to be completely reworked to meet the requirements.
• Consider adding comments to explain the logic, especially for complex queries like Problem 1.
• For Problem 1, consider alternative approaches that might be more efficient with large datasets.