Completed Sql1

[Aniruddh-2512]

No description provided.

[super30admin]

1. BigCountries.sql:

   • Correctness: The query correctly identifies big countries based on the given criteria (area >= 3 million or population >= 25 million). This appears to be a correct solution.
   • Time Complexity: O(n) where n is the number of rows in the World table, as it needs to scan all rows to apply the filter conditions.
   • Space Complexity: O(1) for the query itself, though the result set size depends on how many countries meet the criteria.
   • Code Quality: The code is clean, simple, and follows standard SQL formatting. The column selection and WHERE clause are well-structured.
   • Efficiency: No obvious optimizations needed for this simple query.

2. DeleteDuplicateEmails.sql:

   • Correctness: The solution correctly deletes duplicate emails while keeping the record with the smallest id. This is a standard approach for this problem.
   • Time Complexity: O(n^2) in the worst case due to the self-join, but this is acceptable for this type of operation.
   • Space Complexity: O(n) for the join operation.
   • Code Quality: The code is concise and correct. Using a self-join with a condition to keep the smallest id is a good approach.
   • Efficiency: Could potentially be optimized with window functions in more modern SQL versions, but this solution is fine for most cases.

3. nthHighestSalary.sql:

   • Correctness: The function correctly returns the nth highest salary using LIMIT with offset. The use of DISTINCT ensures correct handling of duplicate salaries.
   • Time Complexity: O(n log n) for the sorting operation, which is efficient for this purpose.
   • Space Complexity: O(1) for the function itself.
   • Code Quality: The code is well-structured with proper variable declaration (M for offset calculation). The use of DISTINCT and ORDER BY is appropriate.
   • Efficiency: The solution is already efficient. One minor improvement could be to handle the case where N is larger than the number of distinct salaries by returning NULL.

General Observations:

• All solutions are correct and follow standard approaches.
• Code formatting is consistent and readable.
• Variable naming is appropriate (like using M for offset calculation).
• The solutions handle the core requirements well.

Areas for Improvement:

• For nthHighestSalary.sql, consider adding a check to return NULL when N is invalid (e.g., N <= 0 or N > number of distinct salaries).
• While not necessary, the BigCountries query could include a comment explaining the criteria for "big" countries.