50 DBMS MCQs with Answers

Question 1

In E-R model, Y is the dominant entity and X is subordinate entity

• If X is deleted, then Y is also deleted
• If Y is deleted, then X is also deleted
• If Y is deleted, then X is not deleted
• None of the above

Question 2

Let R₁ (a, b, c) and R₂ (x, y, z) be two relations in which a is the foreign key of R₁ that refers to the primary key of R₂ . Consider following four options. (a)Insert into R ₁ (b)Insert into R ₂ (c)Delete from R ₁ (d)Delete from R ₂ Which of the following is correct about the referential integrity constraint with respect to above?

• Operations (a) and (b) will cause violation.
• Operations (b) and (c) will cause violation.
• Operations (c) and (d) will cause violation.
• Operations (d) and (a) will cause violation.

Question 3

How to express that some person keeps animals as pets?

• (A)
• (B)
• (C)
• (D)

Question 4

A view of database that appears to an application program is known as

• Schema
• Subschema
• Virtual table
• None of these

Question 5

Which operation is used to extract specified columns from a table?

• Project
• Join
• Extract
• Substitute

Question 6

The relation schemas R₁ and R₂ form a Lossless join decomposition of R if and only if: (a) R₁ ∩ R₂ ↠ (R₁ - R₂) (b) R₁ → R₂ (c) R₁ ∩ R₂ ↠ (R₂ - R₁ ) (d)(R₂ → R₁) ∩ R₂

• (a) and (b) happens
• (a) and (d) happens
• (a) and (c) happens
• (b) and (c) happens

Question 7

In functional dependency Armstrong inference rules refers to

• Reflexivity, Augmentation and Decomposition
• Transitivity, Augmentation and Reflexivity
• Augmentation, Transitivity, Reflexivity and Decomposition
• Reflexivity, Transitivity and Decomposition

Question 8

Which of the following statements is FALSE about weak entity set?

• Weak entities can be deleted automatically when their strong entity is deleted.
• Weak entity set avoids the data duplication and consequent possible inconsistencies caused by duplicating the key of the strong entity.
• A weak entity set has no primary keys unless attributes of the strong entity set on which it depends are included
• Tuples in a weak entity set are not partitioned according to their relationship with tuples in a strong entity set.

Question 9

Relation R has eight attributes ABCDEFGH. Fields of R contain only atomic values. F = {CH -> G, A -> BC, B -> CFH, E -> A, F -> EG} is a set of functional dependencies (FDs) so that F+ is exactly the set of FDs that hold for R. How many candidate keys does the relation R have?

• 3
• 4
• 5
• 6

Question 10

In RDBMS, different classes of relations are created using __________ technique to prevent modification anomalies.

• Functional Dependencies
• Data integrity
• Referential integrity
• Normal Forms