An entity has: (i) a set of properties (ii) a set of properties and values for…
2008
An entity has:
(i) a set of properties
(ii) a set of properties and values for all the properties
(iii) a set of properties and the values for some set of properties may non-uniquely identify an entity
(iv) a set of properties and the values for some set of properties may uniquely identify an entity
Which of the above are valid?
- A.
(i) only
- B.
(ii) only
- C.
(iii) only
- D.
(iv) only
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Correct answer: D
In database theory, an entity instance must be uniquely distinguishable from other instances. While entities possess properties (i), the defining characteristic that validates an entity's identity is the existence of a set of attributes that can uniquely identify it. This corresponds to statement (iv), representing a primary or candidate key. Therefore, option 3 is the correct choice.
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