Relational Algebra(Engineering > Computer Science And Engineering > Dbms Questions And Answers ) Questions and Answers

Question 1. Relational Algebra is a __________ query language that takes two relation as input and produces another relation as output of the query.
  1.    Relational
  2.    Structural
  3.    Procedural
  4.    Fundamental
Explanation:-
Answer: Option C. -> Procedural


ProceduralThis language has fundamental and other operations which are used on relations .


Question 2. Which of the following is used to denote the selection operation in relational algebra ?
  1.    Pi (Greek)
  2.    Sigma (Greek)
  3.    Lambda (Greek)
  4.    Omega (Greek)
Explanation:-
Answer: Option B. -> Sigma (Greek)


Sigma (Greek)The select operation selects tuples that satisfy a given predicate.


Question 3. The ___________ operation, denoted by -, allows us to find tuples that are in one relation but are not in another.
  1.    Union
  2.    Set-difference
  3.    Difference
  4.    Intersection
Explanation:-
Answer: Option B. -> Set-difference


Set-differenceThe expression r - s produces a relation containing those tuples in r but not in s.


Question 4. Which of the following is a fundamental operation in relational algebra ?
  1.    Set intersection
  2.    Natural join
  3.    Assignment
  4.    None of the mentioned
Explanation:-
Answer: Option D. -> None of the mentioned


None of the mentionedThe fundamental operations are select, project, union, set difference, Cartesian product, and rename.


Question 5. For select operation the ________ appear in the subscript and the ___________ argument appears in the paranthesis after the sigma.
  1.    Predicates, relation
  2.    Relation, Predicates
  3.    Operation, Predicates
  4.    Relation, Operation
Explanation:-
Answer: Option A. -> Predicates, relation


Predicates, relation


Question 6. Which is a unary operation:
  1.    Selection operation
  2.    Primitive operation
  3.    Projection operation
  4.    Generalized selection
Explanation:-
Answer: Option D. -> Generalized selection


Generalized selectionGeneralization Selection takes only one argument for operation.


Question 7. The assignment operator is denoted by
  1.    ->
  2.    =
  3.    ==
Explanation:-
Answer: Option D. -> Generalized selection


All of the mentionedThe FULL OUTER JOIN keyword combines the result of both LEFT and RIGHT joins.


Question 8. Which of the following is not outer join ?
  1.    Left outer join
  2.    Right outer join
  3.    Full outer join
  4.    All of the mentioned
Explanation:-
Answer: Option D. -> All of the mentioned


All of the mentionedThe FULL OUTER JOIN keyword combines the result of both LEFT and RIGHT joins.


Question 9. Which is a join condition contains an equality operator:
  1.    Equijoins
  2.    Cartesian
  3.    Natural
  4.    Left
Explanation:-
Answer: Option A. -> Equijoins


Equijoins


Question 10. In precedence of set operators the expression is evaluated from
  1.    Left to left
  2.    Left to right
  3.    Right to left
  4.    From user specification
Explanation:-
Answer: Option B. -> Left to right


Left to rightThe expression is evaluated from left to right according to the precedence.


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