FYUG Even Semester Exam, 2025
COMPUTER SCIENCE: CSCDSM-252
(Database Management System)
UNIT—I
Question 1 (a) 2 Marks
What do you mean by database management system?
A Database Management System (DBMS) is software designed to store, retrieve, and manage data in a database. It acts as an interface between users and the data, ensuring security, integrity, and efficient data handling.
Question 1 (b) 2 Marks
What are schemas and instances?
- Schema: The overall design or logical structure of the database is called the schema.
It is static and defined during database creation.
- Instance: The collection of information stored in the database at a particular moment is called an instance.
It changes whenever data is inserted or deleted.
Question 1 (c) 2 Marks
Differentiate between logical data independence and physical data independence.
| Feature |
Logical Data Independence |
Physical Data Independence |
| Definition |
Ability to change the conceptual schema without affecting external views. |
Ability to change the physical schema without affecting the conceptual schema. |
| Level |
Occurs at the User-Conceptual mapping level. |
Occurs at the Conceptual-Internal mapping level. |
| Complexity |
More difficult to achieve. |
Easier to achieve. |
Question 2 (a) 10 Marks
(i) Explain the architecture of DBMS.
The standard architecture for a DBMS is the Three-Schema Architecture, which separates the physical database from user applications:
- External Level (View Level): Describes only the part of the database relevant to specific users.
- Conceptual Level (Logical Level): Describes what data is stored in the database and what relationships exist among those data.
- Internal Level (Physical Level): Describes how the data is actually stored on the storage media.
(ii) Write about the different data models used in DBMS.
- Relational Model: Represents data as tables (relations) with rows and columns.
- Entity-Relationship (ER) Model: Uses entities, attributes, and relationships to represent the real world.
- Hierarchical Model: Organizes data in a tree-like structure with parent-child relationships.
- Network Model: Similar to hierarchical but allows child nodes to have multiple parents.
- Object-Oriented Model: Represents data as objects, similar to OOP concepts.
Question 2 (b) 10 Marks
(i) Write down the advantages of DBMS.
- Controlled Redundancy: Minimizes duplicate data storage.
- Data Sharing: Allows multiple users to access data simultaneously.
- Data Consistency: Ensures all users see the same accurate data.
- Improved Security: Restricts unauthorized access through permissions.
- Backup and Recovery: Provides mechanisms to restore data after failures.
(ii) What are the different types of relationship? Explain.
- One-to-One (1:1): An entity in A is associated with exactly one entity in B.
- One-to-Many (1:N): An entity in A is associated with any number of entities in B.
- Many-to-One (N:1): Multiple entities in A are associated with one entity in B.
- Many-to-Many (M:N): Multiple entities in A are associated with multiple entities in B.
UNIT—II
Question 3 (b) 2 Marks
What are DDL and DML?
- DDL (Data Definition Language): Used to define database structures like tables (e.g., CREATE, ALTER, DROP).
- DML (Data Manipulation Language): Used to access and manipulate the data (e.g., SELECT, INSERT, UPDATE, DELETE).
Question 4 (a) 10 Marks
Explain different relational algebra operations used in DBMS.
- Select (σ): Extracts rows that satisfy a given predicate.
- Project (π): Selects specific columns from a table.
- Union (∪): Combines all tuples from two compatible relations.
- Set Difference (−): Tuples in one relation but not in the other.
- Cartesian Product (X): Combines every tuple of one relation with every tuple of another.
- Join (⋈): Combines related tuples based on a common attribute.
UNIT—III
Question 6 (b) 10 Marks
What is normalization? Explain different normal forms. Differentiate between 3NF and BCNF.
Normalization: The process of organizing data in a database to reduce redundancy and avoid anomalies.
- 1NF: Eliminates multi-valued attributes; values must be atomic.
- 2NF: In 1NF + eliminates partial functional dependency.
- 3NF: In 2NF + eliminates transitive dependency.
3NF vs BCNF: A table is in 3NF if for every FD X → A, X is a superkey or A is a prime attribute.
BCNF is stricter: for every FD X → A, X must be a superkey.
UNIT—IV
Question 8 (b) 10 Marks
(i) Explain ACID properties of transaction.
- Atomicity: The entire transaction happens at once or not at all.
- Consistency: Database must remain in a consistent state before and after the transaction.
- Isolation: Transactions run independently without interference.
- Durability: Changes are permanent once the transaction is committed.
UNIT—V
Question 10 (b) 10 Marks
What is indexing? Explain different types of indices with example of each.
Indexing: A data structure technique to quickly locate and access data in a database.
- Primary Index: Defined on an ordered data file (e.g., Index on StudentID in a sorted list).
- Clustering Index: Defined on an ordered data file on a non-key field.
- Secondary Index: Defined on fields that are not the search key of the primary index.