done HW5.SQL

[sagar1023]

No description provided.

[super30admin]

1. Correctness:

   • Problem 1 (Report Contiguous Dates): The solution correctly identifies contiguous date ranges for failed and succeeded states. The use of window functions and grouping by the difference between rank and row number is a standard approach for this type of problem.
   • Problem 2 (Student Report By Geography): The solution correctly pivots the data into columns for each continent. The use of ROW_NUMBER() and RIGHT/LEFT JOINs is appropriate.
   • Problem 3 (Average Salary Department vs Company): The solution correctly compares department averages with company averages. The CASE statement handles the comparison logic well.
   • Problem 4 (Game Play Analysis I): The solution correctly finds the first login date for each player using MIN() and GROUP BY.

2. Time Complexity:

   • Problem 1: O(n log n) due to sorting for the window functions.
   • Problem 2: O(n log n) due to sorting for the ROW_NUMBER() function.
   • Problem 3: O(n) for the aggregations.
   • Problem 4: O(n) for the GROUP BY operation.

3. Space Complexity:

   • Problem 1: O(n) for storing the CTE and intermediate results.
   • Problem 2: O(n) for storing the CTEs.
   • Problem 3: O(n) for storing the CTEs.
   • Problem 4: O(n) for the GROUP BY operation.

4. Code Quality:

   • The code is generally well-structured and readable.
   • The use of CTEs improves readability and modularity.
   • Consistent use of aliases and formatting.
   • Minor issues: In Problem 1, the subquery alias 'y' is not descriptive. In Problem 2, the column aliases could be more descriptive (e.g., 'rnk' could be 'row_num').

5. Efficiency:

   • The solutions are efficient for the given problems.
   • No major optimizations are needed, but using more descriptive aliases would improve readability.