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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

Database Management Systems Lecture Notes

Here are comprehensive RDBMS (Relational Database Management System) Notes tailored for BCA, B.Tech, GATE, and Computer Science Engineering students. These notes cover both theory and practical concepts, perfect for exams and interviews.

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RDBMS NOTES (Relational Database Management System)

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1. Introduction to DBMS & RDBMS

DBMS (Database Management System):

A software system that enables users to define, create, maintain, and control access to a database.

RDBMS (Relational DBMS):

A type of DBMS based on the relational model introduced by E.F. Codd. Data is stored in tables (relations).

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2. Key Terminologies

Term	Description
Relation	A table with rows and columns
Tuple	A row in a table
Attribute	A column in a table
Domain	Set of valid values for an attribute
Primary Key	Uniquely identifies each row
Candidate Key	All possible keys that can uniquely identify tuples
Foreign Key	A field that refers to the primary key of another table
Super Key	Set of attributes that uniquely identify a row
Composite Key	A key formed by combining two or more attributes

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3. Advantages of RDBMS

• Data integrity & accuracy

• No data redundancy

• Easy to extend and modify

• Powerful querying using SQL

• Security features with access control

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4. Codd’s 12 Rules (Simplified)

Dr. Edgar F. Codd proposed 12 rules to define a perfect RDBMS. Key ones include:

• Information Rule: All data must be stored in tables.

• Systematic treatment of nulls.

• Data independence (physical and logical).

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5. Normalization

Process of organizing data to reduce redundancy and improve integrity.

Normal Form	Description
1NF	Atomic values (no repeating groups)
2NF	1NF + no partial dependency
3NF	2NF + no transitive dependency
BCNF	Stronger version of 3NF
4NF, 5NF	Handle multi-valued dependencies, join dependencies

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6. SQL (Structured Query Language)

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

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7. Keys and Constraints

• Primary Key: Unique & not null

• Foreign Key: Refers to another table

• Unique Constraint: All values must be unique

• Not Null: Column cannot have NULL values

• Check Constraint: Limits value range in a column

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8. Relational Algebra (Theoretical foundation of SQL)

Operators:

• Selection (σ): Filter rows

• Projection (π): Select columns

• Union (∪)

• Intersection (∩)

• Difference (−)

• Cartesian Product (×)

• Join (⨝): Combine relations based on common attributes

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9. Transactions and ACID Properties

• Atomicity: All or nothing

• Consistency: Valid state transition

• Isolation: No intermediate state exposed

• Durability: Changes persist after commit

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10. Indexing

• Primary Index

• Secondary Index

• Clustered vs Non-clustered Index

Speeds up searching & access time.

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11. ER Model (Entity-Relationship Model)

• Entity: Object (e.g., Student)

• Attribute: Properties (e.g., Name, ID)

• Relationship: Association between entities

• Diagram uses rectangles (entities), ovals (attributes), diamonds (relationships)

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12. Joins in SQL

Join Type	Description
INNER JOIN	Common rows in both tables
LEFT JOIN	All from left + matching from right
RIGHT JOIN	All from right + matching from left
FULL JOIN	All rows from both tables
SELF JOIN	Join table with itself
CROSS JOIN	Cartesian product

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13. Triggers, Views & Stored Procedures

• Trigger: Auto-execute on insert/update/delete

• View: Virtual table

• Stored Procedure: Precompiled SQL code block

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14. Important Topics for GATE

• Relational Algebra & Calculus

• SQL (Nested queries, joins)

• Normalization

• Functional Dependencies

• Transactions & Concurrency

• Indexing & File Organization

• ER to Relational Mapping

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