1. Compare each film DVD's replacement cost to the average cost in the same MPAA rating.(Return columns: title, rating, replacement_cost, average_cost)

2. Compare each film's length to the longest film in its category. (Return columns:  title, name, length, max_length)

3. Create a ranking index by film length. (Return columns:  film_id, title, length, ranking columns)

4. Show the film of the shortest length for each category (Return columns: film_id, title, length, category, ranking)

5. Select out Top 5 customers for each store based on the total payment amount. (Return columns: store_id, customer_id, total_amount, ranking)

6.  Write a query to return the difference of the payment amount between the first movie rental and the second rental for the following customers
-- customer_id in (1, 2, 3, 4, 5, 6, 7, 8, 9, 10).