RDBMS NOTES: Relational Database Management System Notes For BCA, B.tech, GATE & Computer Science Engineering

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Here are RDBMS (Relational Database Management System) Notes for BCA, B.Tech, GATE & Computer Science Engineering students.

1. Introduction to RDBMS

A Relational Database Management System (RDBMS) is a database management system that stores data in tables (relations) and allows operations based on relational algebra.

Key Features of RDBMS:

• Data is stored in tables (rows & columns).
• Supports ACID properties (Atomicity, Consistency, Isolation, Durability).
• Uses SQL (Structured Query Language) for data operations.
• Supports data integrity & normalization.
• Provides multi-user access with security control.

2. RDBMS vs DBMS

Feature	DBMS	RDBMS
Data Storage	In files or hierarchical models	In tables (relations)
Data Integrity	No constraints like primary keys	Uses primary, foreign keys
Normalization	Not supported	Fully supports normalization
Scalability	Less scalable	Highly scalable
Multi-user Support	Limited	Supports multiple users with concurrency control

3. RDBMS Concepts

3.1 Tables, Rows, and Columns

• Table (Relation) → Collection of rows (tuples) and columns (attributes).
• Tuple (Row) → Represents a single record.
• Attribute (Column) → Represents a field in the table.

3.2 Keys in RDBMS

• Primary Key → Unique identifier for each row.
• Foreign Key → Links two tables for relationships.
• Candidate Key → Potential primary key.
• Composite Key → Key formed by combining two or more attributes.
• Super Key → Set of one or more keys that uniquely identify a row.

3.3 Normalization (1NF, 2NF, 3NF, BCNF)

Normalization is used to eliminate redundancy and dependency in databases.

• 1NF (First Normal Form) → Atomicity of data (no multiple values in a column).
• 2NF (Second Normal Form) → No partial dependencies (every non-key attribute depends on the primary key).
• 3NF (Third Normal Form) → No transitive dependencies (removes indirect relationships).
• BCNF (Boyce-Codd Normal Form) → Stricter form of 3NF, ensuring every determinant is a key.

4. SQL (Structured Query Language)

4.1 SQL Commands

• DDL (Data Definition Language): CREATE, ALTER, DROP
• DML (Data Manipulation Language): INSERT, UPDATE, DELETE
• DQL (Data Query Language): SELECT
• DCL (Data Control Language): GRANT, REVOKE
• TCL (Transaction Control Language): COMMIT, ROLLBACK, SAVEPOINT

4.2 SQL Queries Examples

• Create a table:
  CREATE TABLE Students ( ID INT PRIMARY KEY, Name VARCHAR(50), Age INT, Course VARCHAR(20) );
• Insert data:
  INSERT INTO Students (ID, Name, Age, Course) VALUES (1, 'Rahul', 22, 'B.Tech');
• Retrieve data:
  SELECT * FROM Students WHERE Age > 20;
• Update data:
  UPDATE Students SET Course = 'MCA' WHERE ID = 1;
• Delete data:
  DELETE FROM Students WHERE ID = 1;

5. ER Model (Entity-Relationship Model)

The ER Model represents data using Entities, Attributes, and Relationships.

• Entity → Object in the database (e.g., Student, Employee).
• Attribute → Property of an entity (e.g., Student ID, Name).
• Relationship → Connection between entities (e.g., “Enrolled in” between Student and Course).

Types of Relationships:

1. One-to-One (1:1) → Example: Passport & Person.
2. One-to-Many (1:M) → Example: Teacher & Students.

3. Many-to-Many (M:M) → Example: Students & Courses.

6. Transactions & Concurrency Control

6.1 Transactions in RDBMS

A transaction is a sequence of SQL operations performed as a single logical unit of work.

6.2 ACID Properties

1. Atomicity → Ensures complete execution or rollback.
2. Consistency → Ensures database remains in a valid state.
3. Isolation → Ensures transactions do not interfere with each other.
4. Durability → Ensures committed changes are permanent.

6.3 Concurrency Control

Concurrency control techniques manage multiple transactions:

• Locking (Shared & Exclusive Locks)
• Timestamp Ordering
• Optimistic & Pessimistic Concurrency Control

7. Indexing & Performance Optimization

• Indexing improves database performance by allowing faster data retrieval.
• Types of Indexes:
  • Primary Index → Built on primary key.
  • Unique Index → Ensures uniqueness of values.
  • Clustered & Non-Clustered Indexes.

8. RDBMS Applications

• Banking Systems
• E-commerce Websites
• Healthcare Management
• Online Reservation Systems
• Social Media Platforms

9. Important Topics for GATE & B.Tech

• SQL Query Optimization
• Relational Algebra & Calculus
• Normalization & Decomposition
• Transactions & Concurrency
• ER Model & Database Design

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RDBMS NOTES: Relational Database Management System Notes For BCA, B.tech, GATE & Computer Science Engineering

UNIT – I RELATIONAL DATABASE-MANAGEMENT SYSTEM

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