The head of marketing is interested in some opportunities for cross-selling of products. She thinks that the way to identify cross-selling opportunities is to know for each product how many other products are sold to the same customer on the same order (e.g., a product that is bought by a customer in the same order with lots of other products is a better candidate for cross-selling than a product bought by itself).
a. To help the marketing manager, first list the IDs for all the products that have sold in total more than 20 units across all orders. (These are popular products, which are the only products she wants to consider as triggers for potential cross-selling.)
b. Make a new query that lists all the IDs for the orders that include products that satisfy the first query, along with the number of products on those orders. Only orders with three or more products on them are of interest to the marketing manager. Write this query as general as possible to cover any answer to the first query, which might change over time. To clarify, if product X is one of the products that is in the answer set from part a, then in part b we want to see the desired order information for orders that include product X.
c. The marketing manager needs to know what other products were sold on the orders that are in the result for part b. (Again, write this query for the general, not specific, result to the query in part b.) These are products that are sold, for example, with product X from part a, and these are the ones that if people buy that product, we'd want to try to cross-sell them product X because history says they are likely to buy it along with what else they are buying. Write a query to identify these other products by ID and description. It is okay to include "product X" in your result (i.e., you don't need to exclude the products in the result of part a.).