Added solutions for Mock-SQL-3

[arushi2106]

No description provided.

[super30admin]

The student's solution demonstrates a good understanding of SQL concepts and problem-solving approach. Here's a detailed evaluation:

1. Correctness:

• For Market_Analysis_II.sql, the solution correctly identifies users whose second sold item matches their favorite brand. The use of window functions and joins is appropriate.
• For Tournament_winners.sql, the solution correctly identifies the winner for each group based on total score and player_id tiebreaker. The UNION ALL approach to combine scores is correct.

2. Time Complexity:

• Both solutions use window functions (rank() and row_number()) which typically have O(n log n) complexity where n is the number of rows.
• The joins are efficiently implemented and shouldn't cause performance issues.

3. Space Complexity:

• The CTEs create temporary tables in memory, but they're necessary for the solution and don't appear excessive.

4. Code Quality:

• Strengths:
  • Good use of CTEs to break down complex logic into manageable parts
  • Proper indentation and formatting
  • Descriptive column and table aliases
• Areas for improvement:
  • In Market_Analysis_II.sql, the final CASE statement could be simplified to just check if c.user_id is null
  • The column name "2nd_item_fav_brand" should be quoted or renamed to avoid using numbers at the start
  • Consider adding comments to explain complex logic steps

5. Efficiency:

• Both solutions are already quite efficient, but for Tournament_winners.sql, the solution could potentially be optimized by combining some CTEs to reduce the number of temporary tables created.

Potential edge cases to consider:

• Users who haven't sold any items (handled correctly with LEFT JOIN)
• Users who have only sold one item (handled correctly)
• Ties in tournament scores (handled correctly with player_id tiebreaker)