ITPEC FE Morning October 2022 Question 29

Topic: Databases

In a company, the received-orders are monitored monthly based on the customer file, product file, person-in-charge file, and the current month’s received-orders file. When the items of each file are as shown in the table below, which of the following can be retrieved for the received orders of current month and the three (3) previous months using the four (4) files?

FileItemsRemarks
CustomerCustomer code, name, person-in-charge code, amount of orders received in the previous month, amount of orders received two (2) months ago, amount of orders received three (3) months agoThere is one (1) person in charge of each customer
ProductProduct code, name, amount of orders received in the previous month, amount of orders received two (2) months ago, amount of orders received three (3) months ago————
Person-in-chargePerson-in-charge code, name of the person————
Current month’s received ordersCustomer code, product code, amount of orders receivedTotal amount of orders received in the current month

Explanation

Customer-wise received orders by the person in charge — only totals the files hold for all four months can be regrouped, and each customer belongs to exactly one person in charge.

For the three previous months the files keep only totals: per customer in the Customer file and per product in the Product file. No file keeps a customer-by-product breakdown for past months; only the current month's file records customer and product together.

  • •Four months per customer: the previous three from the Customer file, the current month by summing current-month records by customer code
  • •Grouping by person in charge: each customer has one person-in-charge code in the Customer file, and the name comes from the Person-in-charge file, so every customer total falls under exactly one person

Answer (b)

Why not others:

  • •(a) and (d) — both need each customer's orders split by product, which exists only for the current month; past totals are per customer or per product, and the two cannot be crossed
  • •(c) — a person reaches products only through customers, so it needs the same customer-by-product history that the files do not keep

Key rule: Summarised history can be regrouped only along a many-to-one link (each total belongs to exactly one group); a breakdown the totals never recorded cannot be rebuilt.

Databases · AI-written, may contain errors

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