Added Sql5 Q1-4

[arushi2106]

No description provided.

[super30admin]

Let me evaluate each solution separately:

1. Sql5_Q1_ReportContDates_rnk_grprnk.sql:

   • Correctness: The solution correctly identifies continuous date periods for each state (failed/succeeded) using the rank difference technique, which is a standard approach for such problems.
   • Time Complexity: O(n log n) due to the sorting operations in the window functions.
   • Space Complexity: O(n) for storing intermediate results.
   • Code Quality: Well-structured with clear CTEs. The column alias 'date' should be quoted consistently (either all quoted or none).
   • Efficiency: Good approach, though the year filter could be applied earlier in the CTEs for better performance.

2. Sql5_Q2_StudentsByGeo.sql:

   • Correctness: Correctly pivots the data by continent using row numbers for alignment.
   • Time Complexity: O(n log n) for sorting in each CTE.
   • Space Complexity: O(n) for storing intermediate results.
   • Code Quality: Clear structure with CTEs. The RIGHT JOIN with LEFT JOIN combination could be simplified to FULL OUTER JOIN if available.
   • Efficiency: Consider using PIVOT or CROSSTAB if the SQL dialect supports it for better readability.

3. Sql5_Q3_AvgSalDeptCo.sql:

   • Correctness: Correctly compares department averages with company averages.
   • Time Complexity: O(n log n) for the grouping operations.
   • Space Complexity: O(n) for storing intermediate results.
   • Code Quality: Well-structured with meaningful CTE names. The CASE statement could be simplified using SIGN() function if available.
   • Efficiency: Good approach, no major optimizations needed.

4. Sql5_Q4_GamePlayAnalysis.sql:

   • Correctness: Correctly finds the first login date for each player.
   • Time Complexity: O(n log n) for the GROUP BY operation.
   • Space Complexity: O(n) for the grouping operation.
   • Code Quality: Simple and effective. Could add a comment explaining it's finding first login dates.
   • Efficiency: Already optimal for this simple query.

General strengths:

• Consistent use of CTEs for better readability
• Proper use of window functions where needed
• Clear column naming
• Appropriate use of GROUP BY operations

Areas for improvement:

• Consider adding brief comments explaining the purpose of each CTE
• Standardize quoting style for column aliases
• Explore database-specific features like PIVOT for Q2
• Consider adding index hints if performance is critical