How would you handle a multivalue attribute like multiple phone numbers in a relational model?

• A. Create a separate child table with a foreign key to the parent and a value column for each phone number.
• B. Store all phone numbers in a single column as a comma-separated list.
• C. Use a separate database for phone numbers.
• D. Embed multiple values directly in the parent table's attribute as separate columns.

Answer: (A)

Handling multivalue attributes in a relational model relies on normalization: store each value as its own row in a related table rather than packing several values into one column. The best approach is to create a child table that carries a foreign key to the parent and a single value column for the phone number. This lets a single person have many phone numbers without duplicating the parent data or forcing nulls, and it keeps data consistent and easy to validate. For example, a Person table with PersonID and Name, and a PhoneNumbers table with PersonID (FK) and PhoneNumber (and optionally PhoneType). Each phone number becomes its own row, tied to the person. In contrast, putting all numbers in one column as a comma-separated list breaks atomicity and makes querying and updating painful; using a separate database is unnecessary and counterproductive; embedding multiple values as separate columns in the parent table fails as you add more numbers and wastes space.