SQL6 Submitted

[PranathiDeepak]

No description provided.

[super30admin]

Let me evaluate each solution separately:

Problem1.sql:

• Correctness: The solution correctly finds the first login device for each player using a subquery to get the minimum event_date.
• Time Complexity: O(n^2) due to the correlated subquery.
• Space Complexity: O(n) for storing intermediate results.
• Code Quality: Well-structured and readable. Could use a JOIN instead of IN for potentially better performance.
• Efficiency: Could be optimized with a window function (ROW_NUMBER) instead of subquery.

Problem2.sql:

• Correctness: Correctly calculates the running total of games played per player.
• Time Complexity: O(n log n) for the window function partition and sort.
• Space Complexity: O(n) for the window frame.
• Code Quality: Excellent use of window functions, clean and efficient.
• Efficiency: Already optimal for this type of problem.

Problem3.sql:

• Correctness: Correctly finds the shortest distance between any two points.
• Time Complexity: O(n^2) due to the self-join.
• Space Complexity: O(n^2) for the join result.
• Code Quality: Good, but the join condition could be clearer with explicit inequality.
• Efficiency: For large datasets, consider using spatial indexes or more advanced algorithms.

Problem4.sql:

• Correctness: Correctly joins person and address tables with LEFT JOIN to include all persons.
• Time Complexity: O(n) for the join operation.
• Space Complexity: O(n) for the result set.
• Code Quality: Simple and effective, follows best practices.
• Efficiency: Already optimal for this simple query.

Problem5.sql:

• Correctness: Correctly identifies customers with increasing spending year over year.
• Time Complexity: O(n^2) due to the self-join.
• Space Complexity: O(n) for the CTE.
• Code Quality: Complex but well-structured. Could benefit from comments explaining the logic.
• Efficiency: The HAVING clause logic is clever but might be hard to maintain.

General strengths:

• Good understanding of SQL concepts like window functions, joins, and subqueries.
• Appropriate use of CTEs for complex queries.
• Mostly follows SQL best practices.

Areas for improvement:

• Some queries could be optimized for better performance.
• Consider adding comments for complex logic.
• For Problem3, the join condition could be more explicit.