Introduction to Databases

Hey, everyone! In this guide, we’re going to explore Databases, the backbone of modern applications.
From storing user information to managing large-scale analytics, databases make it possible to store, retrieve, and manipulate data efficiently.
Let’s dive into the fundamentals you need to know!

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1. What is a Database?

A database is an organized collection of data that allows for efficient storage, retrieval, and management.
Instead of scattering information across multiple files, databases store data in a structured and centralized way.

Key Features:

• Structured Storage → Keeps data in a well-organized format.
• Efficient Retrieval → Query and get the data you need quickly.
• Data Integrity → Ensures data remains accurate and consistent.
• Security Controls → Restricts unauthorized access.
• Scalability → Handles growth in data and users.

Did You Know?

Databases power almost every app you use — from Instagram’s feed to your online banking transactions!

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2. SQL vs NoSQL

Databases generally fall into two main categories: SQL (Relational) and NoSQL (Non-Relational).

Feature	SQL (Relational)	NoSQL (Non-relational)
Structure	Tables (rows & columns)	Flexible formats (JSON, key-value, graph)
Schema	Fixed	Dynamic
Query Language	SQL	API-based or custom
Scaling	Vertical	Horizontal
Examples	MySQL, PostgreSQL, SQLite	MongoDB, Redis, Cassandra

SQL Databases:

• Store data in tables.
• Use Structured Query Language (SQL) for queries.
• Great for structured, related data.
• Examples: MySQL, PostgreSQL, SQLite.

NoSQL Databases:

• Store data in flexible formats.
• Ideal for dynamic or unstructured data.
• Examples: MongoDB, Cassandra, Firebase.

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3. Basic CRUD Operations

CRUD stands for:

• Create – Insert new data.
• Read – Retrieve data.
• Update – Modify existing data.
• Delete – Remove data.

SQL Example:

-- Create
INSERT INTO users (name, email) VALUES ('John Doe', 'john@example.com');

-- Read
SELECT * FROM users;

-- Update
UPDATE users SET email = 'john.doe@example.com' WHERE id = 1;

-- Delete
DELETE FROM users WHERE id = 1;

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4. Popular Databases

1. MySQL

• Type: Relational, open-source
• Use Case: Widely used for web applications
• Key Advantage: Strong community support

2. MongoDB

• Type: NoSQL document database
• Data Format: Stores data in BSON format
• Key Advantage: Great for flexible schemas

3. PostgreSQL

• Type: Advanced relational database
• Features: Supports JSON, indexing, full-text search
• Key Advantage: Open-source and highly extensible

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5. Connecting Databases to Backend Frameworks

Connecting a database to your backend allows you to store, retrieve, and manipulate application data dynamically. General Steps to Connect Any DB to a Backend Framework

1. Install the relevant driver or ORM
   Examples: mysql2, mongoose, pg, prisma
2. Import the library
   Add it to your backend code using require or import.
3. Configure connection parameters
   Include:- Host, Username, Password, Database name
4. Open the connection
   Establish the connection before handling API requests.
5. Perform CRUD operations
   Use the connection to Create, Read, Update, and Delete data.
6. Close the connection gracefully
   Ensure cleanup when the application stops.

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Quiz Time

1. Which type of database stores data in JSON-like documents?

MySQLMongoDBPostgreSQLOracle

2. Which SQL command is used to retrieve data from a database?

INSERTSELECTUPDATEDELETE

3. In SQL vs NoSQL, which one typically uses a fixed schema?

SQLNoSQLBothNeither

4. Which Node.js package is commonly used to connect to MongoDB?

mysql2mongoosepgsequelize

5. Why do we store database credentials in a .env file?

To make the website fasterTo store frontend design settingsTo hide sensitive information like passwordsTo keep database backups