Which statement is FALSE regarding foreign keys?

Question

Options

• AA foreign key is one or more columns that are associated with a primary key or unique key in
• BA table can have zero or more foreign keys.
• CA foreign key cannot exist without an associated primary or unique key.
• DA table can have only one foreign key defined.

• A
  6% (2)
• B
  3% (1)
• C
  3% (1)
• D
  88% (29)

Explanation

Option D is false because a table can have multiple foreign keys - there is no limit of one; a table can reference several different parent tables simultaneously. Options A, B, and C are all true: a foreign key does reference a primary or unique key in another (or the same) table; a table can have zero foreign keys (no referential constraints required); and a foreign key cannot exist without the corresponding primary or unique key it references, since the database must have something to validate against. Memory tip: Think of a sales order table - it might have a customer_id (FK to Customers), a product_id (FK to Products), and a salesperson_id (FK to Employees) all at once, proving the "only one" rule is clearly wrong.

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