In relational algebra, what is the main purpose of the selection (σ) operator…
2025
In relational algebra, what is the main purpose of the selection (σ) operator when applied to a relation?
- A.
It eliminates duplicate tuples from the relation.
- B.
It filters tuples based on a given condition.
- C.
It merges two relations based on a common attribute.
- D.
It sorts the attributes of the relation in increasing sequence.
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Correct answer: B
The selection operator (σ) in relational algebra is fundamentally designed to filter rows, or tuples, from a relation based on a specified logical condition. When applied, it scans the relation and retains only those tuples that satisfy the predicate, effectively reducing the number of rows while keeping all columns intact. This makes Option B correct because it accurately describes this filtering process.