ITPEC IP April 2026 Question 27

Multiple foreign keys can be defined in a single table — a table may reference several other tables.

A foreign key is a column (or set of columns) whose values must match the primary key of another table, which keeps referential integrity. A table can hold as many as it needs: an Order table can have CustomerCode referencing Customer and ProductCode referencing Product.

Answer (c)

Why not others:

• •(a) — the property a foreign key enforces is referential integrity; a unique constraint is a property of primary keys and unique columns
• •(b) — duplicates are normal: many orders can carry the same CustomerCode
• •(d) — several columns can together form one composite foreign key when they reference a composite primary key

Key rule: A foreign key must match an existing value in the referenced table, but it need not be unique, and a table may have several of them.

Databases · AI-written, may contain errors