Which of the following Relational Algebra operators is unary?
2022
Which of the following Relational Algebra operators is unary?
- A.
Selection
- B.
Natural join
- C.
Left outer join
- D.
Right outer join
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Correct answer: A
Relational algebra operators are classified by the number of input relations required. Selection is a unary operator because it filters tuples from a single input relation based on a predicate condition. In contrast, Natural join and outer joins are binary operators requiring two input relations.