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WorksheetsDBMS Multiple Choice Questions
Total questions: 60
Worksheet time: 33mins
Which of the following statements is TRUE?
All super keys are candidate keys
All candidate keys are super keys
Primary key is always a super key, but may contain NULL
A primary key can be duplicated
In ER diagram, a weak entity must have:
Its own primary key
A partial key and a total participation relationship
A multi-valued key
A key consisting of only foreign attributes
If a relation has multiple candidate keys, which key becomes the primary key?
The first one created
The longest one
The most frequently used one chosen by DBA
Automatically selected by DBMS
Which of the following violates physical data independence?
Reorganizing file structure on disk
Changing indexes
Changing storage format of records
Deleting a column from a table
Which among the following is NOT a responsibility of DBA?
Backup and recovery
Performance tuning
Writing client-side front-end code
Granting privileges
A super key that has no proper subset which is also a super key is called:
Primary key
Candidate key
Composite key
Foreign key
In which DB architecture level can multiple user views exist?
Physical level
Logical level
External level
Internal level
In DBMS, data inconsistency arises mainly due to:
Data normalization
Multiple copies of same data stored independently
Foreign keys
Views
A foreign key can be:
Null if not part of a primary key relationship
Always unique
Always composite
Used only between two weak entities
Which of the following does NOT describe the three-schema architecture correctly?
Separates user applications from physical database
Ensures both physical & logical data independence
Improves security by removing DBA roles
Includes external, conceptual and internal schemas
What is a “view” in the context of a DBMS?
A physical table storing data
A virtual table derived from one or more base tables
A backup file of the database
A graphic user interface module
Which of these statements about a file-processing system is true compared to a DBMS?
It supports ad-hoc queries easily
It offers data independence
It has fixed program-data dependence
It automatically enforces referential integrity
Which database architecture tier is typically responsible for business logic (application layer) in a three-tier architecture?
Tier-1
Tier-2
Tier-3
Tier-0
Which of the following is not a correct pairing of language and its purpose in DBMS?
DDL – define database schema
DML – insert, delete, update data
DCL – manipulate data from tables
DQL – query data from tables
The term “instance” of a database refers to:
The schema of the database
The design of the tables
The data stored in the database at a particular moment
The user interface for the database
What is “schema” in context of a database?
The current content (data) of the database
The storage location of files on disk
The structure or design of the database (tables, relationships)
The backup file format
In an ER diagram, which of the following cannot be represented directly as an attribute?
Multivalued attribute
Derived attribute
Composite attribute
Relationship attribute of many-to-many associations
Which of the following causes data redundancy the most in file processing systems?
Centralized control of data
Independent storage of data by different applications
Normalized structure of records
Use of indexing
In DBMS, which statement about integrity constraints is INCORRECT?
They ensure correctness and validity of data
They may prevent insertion or deletion of invalid data
They guarantee that database is always normalized
They help maintain consistency across relationships
Consider two entities Student and Course with a many-to-many relationship. What must be added to implement this in a relational model?
A view between the two tables
A composite table (junction table) containing foreign keys
A weak entity for Student
A single merged table combining all attributes
SELECT COUNT(*)
Throw error
0
1
*
SELECT 'VIKAS' + 1 --output of this query would be.
Throw error
'VIKAS'
VIKAS
VIKAS1
SELECT COUNT(*) + COUNT(*)
Throw error
0
1
2
Which SQL clause is used to filter records?
ORDER BY
WHERE
GROUP BY
DISTINCT
Which command is used to remove a table?
DELETE
ERASE
DROP
REMOVE
Which join returns only matching records from both tables?
LEFT JOIN
RIGHT JOIN
INNER JOIN
FULL JOIN
Which of the following is a DDL command?
UPDATE
INSERT
CREATE
DELETE
8- SELECT 1 WHERE NULL = NULL
NULL
1
No rows
Error
SELECT MAX(1,3,4)
Throw error
1
3
4
Select Count(SELECT CountryID FROM Country)
Throw error
Will display count of country table
0
1
Given R(A, B, C, D) with FDs: A → B, B → C, C → D. Which is the highest normal form of R?
1NF
2NF
3NF
BCNF
If a decomposition of R into R1 and R2 is lossless, which condition must be true?
R1 ∩ R2 → R1
R1 ∩ R2 → R2
(R1 ∩ R2) → R1 or R2
Both R1 and R2 must be in BCNF
Consider R(A, B, C) with MVD A →→ B. Which decomposition is correct for 4NF?
R1(A, B), R2(A, C)
R1(B, C), R2(A, C)
R1(A, B, C)
Which situation indicates that the relation is not in BCNF even though it is in 3NF?
A non-key attribute determines another non-key attribute
A composite key has a partial dependency
A non-prime attribute determines a key attribute
A determinant is not a candidate key
You decompose a table into 3NF, but some FDs are not preserved. What is the consequence?
Join becomes lossy
Query optimization becomes harder
You cannot enforce all constraints without joins
MVDs will vanish
Relation R(A, B, C, D) has FD: AB → C and C → D. What is the candidate key?
AB
ABC
ABD
A
Which of the following indicates the need for 4NF?
Partial dependency
Transitive dependency
Attribute depends on many independent multi-valued facts
Candidate keys are not unique
In a schema R(A, B, C, D), if A → B and C → D, which decomposition ensures BCNF without losing FDs?
R1(A, B), R2(C, D)
R1(A, C), R2(B, D)
R1(A, B, C), R2(C, D)
R1(A, C, D), R2(B)
Which design choice is preferable when FD preservation is more important than BCNF compliance?
If a decomposition is dependency-preserving but lossy, what does it imply?
Some FDs are lost
Some original tuples cannot be recovered by join
Extra tuples appear after join
The decomposed tables are not in 1NF
Which of the following is a multi-valued dependency?
A →→ B
A → B
A ↔ B
A ⊆ B
A decomposition is lossless if and only if:
No redundancy is removed
The join of decomposed relations gives original relation
All FDs remain preserved
Data duplication occurs
Which condition ensures a lossless-join decomposition for R(A,B,C)?
A →→ B
A → C or C → A
AB → C
C → B only
Which of the following indicates redundancy in a database?
Functional dependency
Partial dependency
Atomic values
Primary key
Normalization is a process used to:
Increase redundancy
Reduce anomalies
Increase file size
Reduce access speed
Which of the following anomalies can normalization reduce?
Insertion, deletion, update
Deadlock
Indexing
Encryption
In alternative design approaches, ER modeling is used for:
Network administration
Conceptual schema design
File system design
Concurrency control
If a relation has attributes that depend on non-key attributes, it violates:
1NF
2NF
3NF
BCNF
A dependency A → B holds if:
Two tuples with same A have same B
Two tuples with same B have same A
A and B are always equal
A is a key
Normalization using MVDs helps remove:
Full dependencies
Partial dependencies
Transitive dependencies
Repeating groups in multiple rows
Which of the following ensures uniqueness of each row in a relational table?
Domain Constraint
Tuple Constraint
Key Constraint
Referential Integrity
Referential Integrity ensures:
Every row has a unique primary key
Foreign key value must match an existing primary key value
Data must be of correct type
No two rows can be identical
Which relational algebra operator is used to rename attributes?
Rename (ρ or Rho)
Select (σ or Sigma)
Project (π or Pi)
Join (⨝)
SQL is considered a:
Procedural language
Object-oriented language
Non-procedural language
Low-level programming language
Which SQL command category does UPDATE belong to?
DDL
DCL
TCL
DML
Which SQL operator is used to combine rows from two tables and remove duplicates?
UNION ALL
UNION
INTERSECT
MINUS
A cursor in SQL is used to:
Store triggers
Define constraints
Process query results row-by-row
Update indexes
Which JOIN returns records only when matching values exist in both tables?
LEFT JOIN
FULL JOIN
INNER JOIN
CROSS JOIN
In Relational Calculus, Tuple Relational Calculus (TRC) uses:
Variables that range over domains
Variables that range over tuples
Procedural expressions
Algebraic operations
10. Which of the following describes a trigger?
A database object that automatically executes a specified action in response to certain events.
A type of user interface element used to start a program.
A command used to retrieve data from a database.
A tool for monitoring network traffic.
