Done Mock SQL 2

[sagar1023]

No description provided.

[super30admin]

1. Correctness:

   • For problem 1045, the solution correctly identifies customers who bought all products by comparing the count of distinct products bought by each customer with the total count of products available. This approach is correct.
   • For problem 1070, the solution correctly identifies the first year of sales for each product by using a subquery to find the minimum year for each product. This is also correct.

2. Time Complexity:

   • For problem 1045, the solution involves a join and a group by operation, which typically run in O(n log n) time where n is the number of records. The subquery to count products is O(m) where m is the number of products. Overall, this is efficient.
   • For problem 1070, the solution uses a subquery with a group by, which is O(n log n) where n is the number of sales records. This is also efficient.

3. Space Complexity:

   • For both problems, the space complexity is O(n) for storing intermediate results in the CTE and subqueries. This is reasonable for typical database operations.

4. Code Quality:

   • The code is generally well-structured and readable. However, there are a few areas for improvement:
     • The use of single quotes for column aliases (e.g., 'key_count') is not standard SQL practice. Backticks or double quotes are preferred.
     • The comments (e.g., "# 1045 Customers Who Bought All Products") are not standard SQL comments. Use "--" for single-line comments or "/* */" for multi-line comments.
     • The formatting could be improved for better readability, such as consistent indentation and spacing.

5. Efficiency:

   • The solutions are already quite efficient. However, for problem 1070, an alternative approach using window functions (e.g., ROW_NUMBER()) might be more readable and potentially more efficient for large datasets.