Everything you need to ace Database Concepts— in one place!
These Database Concepts Notes are carefully crafted to align with the latest CBSE syllabus, covering every important topic in a clean, point-to-point format. Written in simple, accessible language, the notes help you build a strong understanding without getting lost in lengthy, complicated explanations.

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Database Concepts

What is Database?

• Database is a collection of related information that is organized in such a way that supports for easy access, modify and maintain data.
• The contents of a database are obtained by combining data from all the different sources in an organization.

What is DBMS?

• DBMS refers to Database Management System, which is special software package used to manage database.
• DBMSs are specially designed applications to create connection between user and program, and to store data in an organized manner.
• It allows users to create, store, retrieve, modify, and manage databases.
• Examples of DBMS are Microsoft Access, MySQL, PostgreSQL, SQLite, Microsoft SQL Server, Oracle, dBASE, FoxPro etc.

Need of DBMS

• To reduce unnecessary duplication of data.
• To maintain consistency and accuracy of data.
• To manage large amount of data without complexity
• To make data easily available to multiple users.
• To provide security and protect confidential information.
• To access, modify, and manage data easily through a user-friendly interface.

Relational Data Model

• The Relational Data Model was proposed by Edgar F. Codd in 1969.
• In this model, data is organized in the form of related tables called relations.
• A table consists of rows and columns, where rows represent records (tuples) and columns represent attributes.
• Each table in a relational database has a unique name and stores related information in an organized manner.
• Relations in a database are connected with each other using common attributes to retrieve meaningful information.
• The DBMS follows Relational Data Model is called RDBMS (Relational Database Management System)

Relational Data Model Terminologies | RDBMS Terminologies

• Attribute: Attributes are the columns or fields of a table that store specific information.
• Tuple: Each row or record in a table is called a tuple. It contains related values of different attributes.
• Domain: Domain is the set of possible values that an attribute can store.
• Degree: The total number of attributes (columns) in a relation is called its degree.
• Cardinality: The total number of tuples (rows) in a relation is called its cardinality.

Example

Student_ID	Name	Class	Marks
101	Rahul	XII	85
102	Priya	XI	90
103	Aman	XII	78
104	Neha	XI	88

Attributes: Student_ID, Name, Class, Marks
Tuple: (101, Rahul, XII, 85)
Degree: 4 (Total number of columns)
Cardinality: 4 (Total number of rows)
Domain Example: Student_ID → Integer values, Name → Character/String values

Keys in Relational Database

Keys are used to maintain data integrity, uniquely identify records, and establish relationships between tables.

Primary Key

• A primary key is a column or group of columns that uniquely identifies each record in a table.
• Example: In the STUDENT table, Ad_No can be the Primary Key because each admission number is unique.

Candidate Key

• A candidate key is a column or set of columns that can uniquely identify records and can become a primary key.
• Example: Ad_No may act as a Candidate Key.

Alternate Key

• The candidate keys that are not selected as the primary key are called alternate keys.
• Example: If Email_ID and Ad_No are candidate keys and Ad_No is selected as the primary key, then Email_ID becomes the Alternate Key.

Foreign Key

• A foreign key is a column in one table that creates a relationship with the primary key of another table.
• Example: If Student_ID is the Primary Key in the STUDENT table and is used in the MARKS table, then Student_ID in MARKS becomes a Foreign Key.

Example of DBMS Keys

STUDENT Table

Student_ID	Email_ID	Name	Class
101	rahul@gmail.com	Rahul	XII
102	priya@gmail.com	Priya	XI

MARKS Table

Student_ID	Subject	Marks
101	English	85
102	Maths	90

• Primary Key: Student_ID uniquely identifies each student in the STUDENT table.
• Candidate Keys: Student_ID and Email_ID are candidate keys because both contain unique values.
• Alternate Key: If Student_ID is selected as the Primary Key, then Email_ID becomes the Alternate Key.
• Foreign Key: Student_ID in the MARKS table is a Foreign Key because it creates a relationship with the STUDENT table.

You’ve completed the theory of Database Concepts—now it’s time to learn how to create, manage, and access data using SQL and Python Connectivity with SQL—the most important and practical section of Unit 3 Database Management of Computer Science Class 12.
Access the notes through the links below.

Structured Query Language Class 12 CS Notes

Python Connectivity with SQL Class 12 CS Notes