BCA 5th Sem Most Important Questions Of Introduction Of DBMS
Here are precise answers to your questions based on a standard DBMS syllabus, which aligns well with the CCSU curriculum:
1. What do you mean by DBMS?
A Database Management System (DBMS) is software that enables users to define, create, maintain, and manage data in a database. It ensures efficient data organization, storage, and retrieval while providing features like data security and concurrent access.
2. What do you mean by DML and DDL?
- DML (Data Manipulation Language): Commands used to manipulate data in the database. Examples:
SELECT,INSERT,UPDATE,DELETE. - DDL (Data Definition Language): Commands used to define or modify the database structure. Examples:
CREATE,ALTER,DROP.
3. Advantages and Disadvantages of DBMS
Advantages:
- Data consistency and integrity.
- Easy data sharing among multiple users.
- Data security and authorization mechanisms.
- Backup and recovery.
- Reduced data redundancy.
Disadvantages:
- High initial cost of hardware and software.
- Complexity in implementation and management.
- Requires skilled personnel.
- Performance overhead in large-scale databases.
4. What are attributes? Give examples.
Attributes represent the properties or characteristics of an entity in a database.
Example:
- Entity: Student
Attributes:Student_ID,Name,Age,Course.
5. Define Primary Key, Not Null Key, and Unique Key
- Primary Key: A unique identifier for each record in a table. Cannot be null.
Example:Student_ID. - Not Null Key: Ensures a column cannot have NULL values.
Example:Name. - Unique Key: Ensures all values in a column are unique but allows one NULL.
Example:Email.
6. What are anomalies in 1NF?
1NF anomalies arise when:
- Data is not atomic (e.g., storing multiple phone numbers in one field).
- Redundancy increases chances of update, insert, and delete anomalies.
7. Explain ER Diagram
An Entity-Relationship Diagram (ERD) is a visual representation of entities, their attributes, and relationships in a database.
- Entities: Objects or items (e.g., Student).
- Attributes: Characteristics (e.g., Name, ID).
- Relationships: Connections between entities (e.g., Student enrolls in Course).
8. Briefly explain security and authorization.
- Security: Protecting data against unauthorized access.
- Authorization: Granting permissions to users to access specific data or operations.
9. What do you mean by referential integrity?
It ensures consistency of relationships between tables. A foreign key in one table must correspond to a primary key in another table or be NULL.
10. Explain Hashing in brief.
Hashing is a technique for mapping data to a fixed-size value (hash code) to enable fast access. It's commonly used in indexing.
11. What are the pitfalls of lock-based protocols?
- Deadlock: Two transactions wait indefinitely for each other.
- Starvation: A transaction never gets access due to high-priority transactions.
- Overhead: Managing locks increases system load.
12. Explain specialization and generalization in ER diagram with examples.
- Specialization: Dividing an entity into sub-entities based on attributes.
Example: Employee → Manager, Engineer. - Generalization: Combining sub-entities into a single generalized entity.
Example: Car, Bike → Vehicle.
13. What do you understand by RDBMS? Difference between DBMS and RDBMS.
- RDBMS (Relational DBMS): A DBMS that stores data in tables (relations). Example: MySQL.
Difference:
- DBMS lacks relations, while RDBMS uses tables with keys.
- RDBMS supports SQL and ensures ACID properties.
14. Define Normal Forms
- 1NF: Atomic data, no repeating groups.
- 2NF: 1NF + No partial dependency.
- 3NF: 2NF + No transitive dependency.
15. Characteristics of SQL & Aggregate Functions
Characteristics:
- Declarative language.
- Standardized commands.
- Can manage large datasets.
Aggregate Functions:
- COUNT(): Counts rows.
Example:COUNT(*). - SUM(): Adds values.
Example:SUM(Salary). - AVG(): Calculates average.
Example:AVG(Age). - MAX(): Finds max value.
Example:MAX(Marks). - MIN(): Finds min value.
Example:MIN(Price).
16. Explain superclass, inheritance, and generalization with examples.
- Superclass: A general entity.
Example: Vehicle. - Inheritance: Subclasses inherit superclass attributes.
Example: Car, Bike inherit Vehicle. - Generalization: Combining subclasses into a superclass.
17. What is a transaction? State diagram
A transaction is a unit of work that must be executed completely or rolled back.
State Diagram:
States:
- Active
- Partially committed
- Committed
- Failed
- Aborted
18. Define E-R Diagram & Example (Library Management)
An E-R Diagram is a conceptual data model using entities, attributes, and relationships.
Library Management System Example:
- Entities: Book, Member, Librarian.
- Attributes:
Book_ID,Name,Issue_Date.
19. Who are data administrators? Functions of DBAs
- Data Administrator: Manages database policies, design, and architecture.
- DBA Functions:
- Backup and recovery.
- Performance tuning.
- Security management.
20. Short Notes
i) Strong and Weak Entity:
- Strong Entity: Exists independently. Example:
Employee. - Weak Entity: Depends on a strong entity. Example:
Dependent.
ii) Different levels of data abstraction:
- Physical Level: How data is stored.
- Logical Level: Structure of the database.
- View Level: User interface.
iii) Database Recovery Techniques:
- Log-based recovery.
- Shadow paging.
- Checkpoints.
