Computer Science

Database Concepts & Relational Data Model MCQs | 25 Practice Questions with Answers | CBSE Class 12 Computer Science

Class 12 · Computer Science

Database Concepts & Relational Data Model MCQs (25 Questions)

Practice these multiple-choice questions to strengthen your understanding of Database Concepts and the Relational Data Model. Click Show Answer to reveal the correct answer and explanation.

Q1. What is a database?

A. A programming language.
B. A collection of related data organized for easy access and management.
C. A computer network.
D. A spreadsheet only.

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Answer: B. A collection of related data organized for easy access and management.

Explanation: A database stores related data in an organized manner so that it can be easily accessed, managed, and updated.

Q2. DBMS stands for:

A. Database Memory System
B. Data Base Management System
C. Data Backup Management System
D. Database Machine Software

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Answer: B. Data Base Management System

Explanation: A DBMS is software used to create, manage, retrieve, and manipulate databases.

Q3. Which of the following is an advantage of using a DBMS?

A. Reduces data redundancy
B. Improves data security
C. Enables data sharing
D. All of these

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Answer: D. All of these.

Explanation: A DBMS reduces redundancy, improves security, ensures consistency, and supports data sharing.

Q4. Which data model is commonly used in modern database systems?

A. Hierarchical Model
B. Network Model
C. Relational Model
D. Object Model

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Answer: C. Relational Model

Explanation: The relational data model organizes data into tables (relations).

Q5. In the relational model, a table is called a:

A. Domain
B. Tuple
C. Relation
D. Attribute

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Answer: C. Relation

Explanation: A table in the relational model is known as a relation.

Q6. In a relation, a column is known as a:

A. Tuple
B. Record
C. Attribute
D. Domain

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Answer: C. Attribute

Explanation: Each column in a table represents an attribute.

Q7. In a relation, a row is called a:

A. Domain
B. Tuple
C. Attribute
D. Field

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Answer: B. Tuple

Explanation: A tuple represents one complete record in a relation.

Q8. What is a domain in a relational database?

A. A table name
B. The set of valid values for an attribute
C. A row in a table
D. A database software

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Answer: B. The set of valid values for an attribute.

Explanation: A domain specifies the permissible values that an attribute can store.

Q9. The degree of a relation refers to the:

A. Number of rows
B. Number of tables
C. Number of columns
D. Number of databases

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Answer: C. Number of columns.

Explanation: Degree is the total number of attributes (columns) in a relation.

Q10. The cardinality of a relation refers to the:

A. Number of columns
B. Number of rows
C. Number of databases
D. Number of keys

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Answer: B. Number of rows.

Explanation: Cardinality is the total number of tuples (rows) present in a relation.

Q11. Which key uniquely identifies each record in a table?

A. Foreign Key
B. Alternate Key
C. Primary Key
D. Composite Key

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Answer: C. Primary Key

Explanation: A primary key uniquely identifies every record in a relation and cannot contain duplicate or NULL values.

Q12. A candidate key is:

A. A key used only in foreign tables.
B. An attribute that can uniquely identify each record.
C. A duplicate key.
D. A key that always contains NULL values.

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Answer: B. An attribute that can uniquely identify each record.

Explanation: A candidate key is any attribute or combination of attributes that can uniquely identify a tuple.

Q13. An alternate key is:

A. The selected primary key.
B. A candidate key that is not selected as the primary key.
C. A duplicate primary key.
D. A foreign key.

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Answer: B. A candidate key that is not selected as the primary key.

Explanation: Candidate keys that are not chosen as the primary key are called alternate keys.

Q14. Which key establishes a relationship between two tables?

A. Candidate Key
B. Alternate Key
C. Foreign Key
D. Composite Key

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Answer: C. Foreign Key

Explanation: A foreign key refers to the primary key of another table, creating a relationship between the two tables.

Q15. A primary key can contain:

A. Duplicate values only.
B. NULL values only.
C. Neither duplicate nor NULL values.
D. Duplicate and NULL values.

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Answer: C. Neither duplicate nor NULL values.

Explanation: Every primary key value must be unique and cannot be NULL.

Q16. Which statement about a candidate key is correct?

A. There can be only one candidate key in a table.
B. A table may have multiple candidate keys.
C. Candidate keys may contain duplicate values.
D. Candidate keys cannot become primary keys.

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Answer: B. A table may have multiple candidate keys.

Explanation: A relation can have several candidate keys, but only one of them is selected as the primary key.

Q17. Which of the following can be a foreign key?

A. An attribute that refers to the primary key of another table.
B. An attribute containing duplicate values only.
C. A calculated field.
D. A row in a table.

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Answer: A.

Explanation: A foreign key establishes a relationship by referring to the primary key of another table.

Q18. Which key is selected from the available candidate keys?

A. Alternate Key
B. Foreign Key
C. Primary Key
D. Composite Key

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Answer: C. Primary Key

Explanation: One candidate key is selected as the primary key based on suitability.

Q19. Which statement is true about alternate keys?

A. They are always foreign keys.
B. They may contain duplicate values.
C. They are candidate keys that are not chosen as the primary key.
D. They are used only in network databases.

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Answer: C.

Explanation: Candidate keys that are not selected as the primary key are known as alternate keys.

Q20. Which statement correctly describes a foreign key?

A. It always contains unique values.
B. It uniquely identifies every record in the same table.
C. It refers to the primary key of another table to establish a relationship.
D. It is selected from alternate keys.

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Answer: C.

Explanation: A foreign key references the primary key of another table and helps maintain relationships between tables.

Q21. Consider the following table:

STUDENT

+-----------+----------+-------+
| RollNo    | Name     | Class |
+-----------+----------+-------+
| 101       | Aman     | XII   |
| 102       | Riya     | XII   |
| 103       | Mohit    | XI    |
+-----------+----------+-------+

Which attribute is the most suitable Primary Key?

A. Name
B. Class
C. RollNo
D. All of these

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Answer: C. RollNo

Explanation: RollNo uniquely identifies each student, making it the best choice for the primary key.

Q22. A STUDENT table contains the attributes RollNo, AdmissionNo, and Name. Both RollNo and AdmissionNo uniquely identify every student. If RollNo is selected as the Primary Key, then AdmissionNo becomes the:

A. Foreign Key
B. Candidate Key
C. Alternate Key
D. Composite Key

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Answer: C. Alternate Key

Explanation: Since AdmissionNo is also a candidate key but is not selected as the primary key, it becomes an alternate key.

Q23. Consider two tables:

STUDENT
RollNo (Primary Key)
Name

MARKS
RollNo
Physics
Chemistry

In the MARKS table, RollNo acts as a:

A. Candidate Key
B. Alternate Key
C. Foreign Key
D. Composite Key

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Answer: C. Foreign Key

Explanation: The RollNo in the MARKS table refers to the primary key of the STUDENT table, making it a foreign key.

Q24. Which statement is correct regarding the relational data model?

A. Data is organized in tables (relations).
B. Each row is called a tuple.
C. Each column is called an attribute.
D. All of these.

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Answer: D. All of these.

Explanation: In the relational model, data is stored in tables called relations. Rows are tuples, and columns are attributes.

Q25. Which statement about databases is correct?

A. A DBMS helps manage and organize data efficiently.
B. A primary key uniquely identifies each record.
C. A foreign key establishes relationships between tables.
D. All of these.

Show Answer

Answer: D. All of these.

Explanation: A DBMS organizes data efficiently, a primary key uniquely identifies records, and a foreign key links related tables.

Answer Key

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	B	10	B	19	C
2	B	11	C	20	C
3	D	12	B	21	C
4	C	13	B	22	C
5	C	14	C	23	C
6	C	15	C	24	D
7	B	16	B	25	D
8	B	17	A
9	C	18	C

Practice Tips

Understand the difference between a Database and a DBMS. A database stores data, while a DBMS is the software used to manage it.
Remember the basic terms of the Relational Data Model:
- Relation = Table
- Tuple = Row (Record)
- Attribute = Column (Field)
- Domain = Set of valid values for an attribute
- Degree = Number of columns
- Cardinality = Number of rows
Revise the different types of keys:
- Candidate Key – Can uniquely identify each record.
- Primary Key – Selected candidate key that uniquely identifies each record and cannot contain duplicate or NULL values.
- Alternate Key – Candidate key not selected as the primary key.
- Foreign Key – Attribute that refers to the primary key of another table to establish relationships.
Practice identifying keys from tables, as CBSE frequently asks application-based questions on primary, alternate, and foreign keys.
Remember:
- Degree = Columns
- Cardinality = Rows
Focus on table-based scenarios and relationship-based questions, as they are commonly asked in CBSE board examinations.

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	B	10	B	19	C
2	B	11	C	20	C
3	D	12	B	21	C
4	C	13	B	22	C
5	C	14	C	23	C
6	C	15	C	24	D
7	B	16	B	25	D
8	B	17	A
9	C	18	C

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	B	10	B	19	C
2	B	11	C	20	C
3	D	12	B	21	C
4	C	13	B	22	C
5	C	14	C	23	C
6	C	15	C	24	D
7	B	16	B	25	D
8	B	17	A
9	C	18	C

Q.No.	Answer	Q.No.	Answer	Q.No.	Answer
1	B	10	B	19	C
2	B	11	C	20	C
3	D	12	B	21	C
4	C	13	B	22	C
5	C	14	C	23	C
6	C	15	C	24	D
7	B	16	B	25	D
8	B	17	A
9	C	18	C