Using the basic ER and relational models, which of the following statements is…
2012
Using the basic ER and relational models, which of the following statements is INCORRECT?
- A.
An attribute of an entity can have more than one value
- B.
An attribute of an entity can be composite
- C.
In a row of a relational table, an attribute can have more than one value
- D.
In a row of a relational table, an attribute can have exactly one value or a NULL value
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Correct answer: C
Answer: Option C
Explanation:
Option A: Correct. In the ER model, an attribute of an entity can be multivalued. For example, a Person entity can have multiple phone numbers.
Option B: Correct. The ER model supports composite attributes, such as an address made up of street, city, and postal code.
Option C: Incorrect. In a relational table, each attribute value in a row must be atomic, meaning exactly one value or NULL. Multiple values in one attribute of a row violate the relational model and First Normal Form (1NF).
Option D: Correct. In the relational model, each attribute value in a row can be exactly one atomic value or NULL.
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