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Following question was asked in the exam. The correct answer to this question is 2. But, I feel that it is a wrong answer. Option 2 is an example of instance of a relation and not an example of instance of a relation schema.

According to Wikipedia article:

The term relation schema refers to a heading paired with a set of constraints defined in terms of that heading. A relation can thus be seen as an instantiation of a relation schema if it has the heading of that schema and it satisfies the applicable constraints.

Q. Identify the correct statement.

1) employee (id#, emp_name) is a relation instance

2) {12, Jessica} is an instance of a relation schema

3) {12, Jessica} specifies a relation schema

4) {12, Jessica} is neither a relation schema nor an instance of a relation

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