ITPEC IP April 2025 Question 26

Customers with both Employee code and Region code as foreign keys — table A takes a name from each of the other two tables, so Customers must reference both.

Table A holds, per customer, Customer name and Representative name, which belong to the customer itself, plus two names that live elsewhere:

• •Employee name is only in Employees in charge, reached through its primary key Employee code
• •Region name is only in Regions, reached through its primary key Region code

To join a customer to its employee in charge and to its region, each customer row must carry both codes as foreign keys. Option (d) has Customer code as primary key, the customer's own attributes, and both foreign keys.

Answer (d)

Why not others:

• •(a) — no foreign key at all, so Customers cannot be joined to either table and neither Employee name nor Region name can be obtained
• •(b) — Employee code gives Employee name, but without Region code the Region name is missing
• •(c) — Region code gives Region name, but without Employee code the Employee name is missing

Key rule: To join tables, the referencing table must hold the primary key of each table it draws data from as a foreign key; one foreign key per referenced table.

Databases · AI-written, may contain errors