GATE CS 2023 Q6 — Relational Model: Relational Algebra

In relational database systems, we define the fundamental properties of a relation as follows:

• Degree (or Arity): The number of attributes (columns) in the relation schema. For example, a relation $R(A, B, C)$ has a degree of $3$.
• Cardinality: The number of tuples (rows) currently stored in the relation.

Let's evaluate the given options:

• Option A: Number of attributes of its relation schema. This is the correct definition of the degree (or arity) of a relation.
• Option B: Number of tuples stored in the relation. This defines the cardinality of the relation, not its degree.
• Option C: Number of entries in the relation. This is an informal term that typically refers to the number of tuples or individual data values, which is incorrect.
• Option D: Number of distinct domains of its relation schema. Multiple attributes in a schema can share the same domain (e.g., both Home_Phone and Work_Phone can share the domain of 10-digit phone numbers). Thus, the number of distinct domains does not represent the degree.

Therefore, Option A is the correct answer.