SQL5 Submitted

[PranathiDeepak]

No description provided.

[super30admin]

1. Correctness:

   • Problem1.sql: The solution correctly identifies consecutive periods of 'failed' and 'succeeded' states in 2019. The use of window functions and grouping by the difference between ranks is a standard approach for this type of problem.
   • Problem2.sql: The solution correctly pivots the student data by continent using row numbers for alignment. This is a valid approach for the problem.
   • Problem3.sql: The solution correctly compares department averages to company averages by month. The CASE statement handles the comparison logic well.
   • Problem4.sql: The solution correctly identifies the first login date for each player using RANK().

2. Time Complexity:

   • All solutions use window functions (RANK(), ROW_NUMBER()) which typically run in O(n log n) time due to sorting.
   • The grouping operations in Problem1.sql and Problem3.sql add additional O(n) complexity.
   • Overall time complexity is reasonable for these problems.

3. Space Complexity:

   • The CTEs create temporary tables in memory, but they're necessary for the solutions.
   • Space complexity is O(n) for all solutions, which is expected for these problems.

4. Code Quality:

   • Strengths:
     • Consistent use of CTEs for better readability.
     • Proper use of window functions.
     • Good column aliasing.
   • Areas for improvement:
     • Problem1.sql: The subquery could be named more descriptively than 'y'.
     • Problem2.sql: The RIGHT JOIN could be confusing; a FULL OUTER JOIN would be more intuitive but isn't available in MySQL.
     • Problem4.sql: The RANK() could be replaced with ROW_NUMBER() since we only need the first row.

5. Efficiency:

   • Problem1.sql: Could add an index on the date columns for better performance.
   • Problem2.sql: The multiple CTEs are necessary but could be optimized with proper indexing on the continent column.
   • Problem3.sql: The JOIN between companyAvg and deptAvg is efficient.
   • Problem4.sql: Adding an index on (player_id, event_date) would improve performance.