This is the DBMS questions and answers section on "Relational Algebra" with explanation for various interview, competitive examination and entrance test. Solved examples with detailed answer description, explanation are given and it would be easy to understand.
1. Relational Algebra is a __________ query language that takes two relation as input and produces another relation as output of the query.
- A. Relational
- B. Structural
- C. Procedural
- D. Fundamental
Answer: Option C
Explanation:
Procedural
This language has fundamental and other operations which are used on relations .
2. Which of the following is a fundamental operation in relational algebra ?
- A. Set intersection
- B. Natural join
- C. Assignment
- D. None of the mentioned
Answer: Option D
Explanation:
None of the mentioned
The fundamental operations are select, project, union, set difference, Cartesian product, and rename.
3. Which of the following is used to denote the selection operation in relational algebra ?
- A. Pi (Greek)
- B. Sigma (Greek)
- C. Lambda (Greek)
- D. Omega (Greek)
Answer: Option B
Explanation:
Sigma (Greek)
The select operation selects tuples that satisfy a given predicate.
4. For select operation the ________ appear in the subscript and the ___________ argument appears in the paranthesis after the sigma.
- A. Predicates, relation
- B. Relation, Predicates
- C. Operation, Predicates
- D. Relation, Operation
Answer: Option A
Explanation:
Predicates, relation
5. The ___________ operation, denoted by -, allows us to find tuples that are in one relation but are not in another.
- A. Union
- B. Set-difference
- C. Difference
- D. Intersection
Answer: Option B
Explanation:
Set-difference
The expression r - s produces a relation containing those tuples in r but not in s.
