Which one of the options given below refers to the degree (or arity) of a…
2023
Which one of the options given below refers to the degree (or arity) of a relation in relational database systems?
- A.
Number of attributes of its relation schema.
- B.
Number of tuples stored in the relation.
- C.
Number of entries in the relation.
- D.
Number of distinct domains of its relation schema.
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Correct answer: A
Key point: the degree (arity) of a relation is the number of attributes (columns) in its relation schema.
Definition: Degree (arity) = number of attributes in the schema.
Example: For relation Student(ID, Name, Age), the degree is 3 because there are three attributes.
Contrast: Cardinality refers to the number of tuples (rows) stored in the relation; counting distinct domains is different and may be less than or equal to the number of attributes if multiple attributes share a domain.