MongoDB Installation and Basic CRUD Operations

What is MongoDB?

MongoDB is a NoSQL database that stores data in flexible, JSON-like documents. It’s schema-less, meaning the structure of the data can evolve over time.

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Let’s see how RDBMS and MongoDB differ:

Key Features:

• 📄 Document-oriented (stores data in JSON-like documents).
• 📊 High scalability and performance.
• 🗄️ Schema-less, meaning flexible data structures.
• 🔄 High availability through replication.
• 🛠️ Supports complex queries with the Aggregation Framework.

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Installation Steps

Step 1: Download MongoDB

1. Visit the MongoDB Download Center.
2. Select your operating system (Windows, macOS, or Linux) and download the appropriate version.

Step 2: Install MongoDB

• For Windows:
  • Run the .msi file and complete the setup.
  • Add the MongoDB bin folder to your system PATH for easy access.
• For macOS (Homebrew):

  brew tap mongodb/brew
  brew install mongodb-community

• For Linux: Use your package manager, e.g., apt for Ubuntu:

  sudo apt update
  sudo apt install -y mongodb

Step 3: Start MongoDB

1. Start the MongoDB server:

   mongod --dbpath <path_to_data_directory>

   Replace <path_to_data_directory> with the path where you want to store data.

2. Connect to the MongoDB shell:

   mongo

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Basic CRUD Operations in MongoDB

CRUD stands for Create, Read, Update, and Delete. Let’s use a collection named students .

1. Create (Insert)

Use the insertOne() or insertMany() methods to add data.

// Insert one document
use school;
db.students.insertOne({ name: "Rajesh Kumar", age: 20, city: "Delhi" });

// Insert multiple documents
db.students.insertMany([
  { name: "Priya Sharma", age: 19, city: "Mumbai" },
  { name: "Amit Singh", age: 22, city: "Bangalore" }
]);

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2. Read (Find)

Query data using the find() or findOne() methods.

// Find all documents
db.students.find();

// Find documents with a specific condition
db.students.find({ city: "Mumbai" });

// Find documents with age greater than 20
db.students.find({ age: { $gt: 20 } });

// Find one document
db.students.findOne({ name: "Priya Sharma" });

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3. Update

Use updateOne(), updateMany(), or replaceOne() to modify data.

// Update one document
db.students.updateOne(
  { name: "Rajesh Kumar" },
  { $set: { age: 21 } }
);

// Update multiple documents
db.students.updateMany(
  { city: "Mumbai" },
  { $set: { status: "Active" } }
);

// Replace a document
db.students.replaceOne(
  { name: "Amit Singh" },
  { name: "Amit Singh", age: 23, city: "Hyderabad" }
);

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4. Delete

Use deleteOne() or deleteMany() to remove data.

// Delete one document
db.students.deleteOne({ name: "Priya Sharma" });

// Delete multiple documents
db.students.deleteMany({ city: "Mumbai" });

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Aggregation Framework

Aggregation allows processing and analyzing data. Let’s explore with examples:

Example 1: Grouping

Count the number of students by city:

db.students.aggregate([
  { $group: { _id: "$city", count: { $sum: 1 } } }
]);

Example 2: Average Age

Calculate the average age of students:

db.students.aggregate([
  { $group: { _id: null, avgAge: { $avg: "$age" } } }
]);

Example 3: Sorting

Sort students by age in descending order:

db.students.aggregate([
  { $sort: { age: -1 } }
]);

To sort students by age in ascending order, use the $sort stage in the aggregation pipeline with age: 1 (where 1 indicates ascending order):

db.students.aggregate([
  { $sort: { age: 1 } }
]);

This will return the list of students sorted from the youngest to the oldest. If you are not using aggregation, you can achieve the same with a simple find() and sort():

db.students.find().sort({ age: 1 });

Both methods will work, so you can choose based on your needs! 😊

Useful Commands

List all databases:

show dbs;

Switch to (or create) a database:

use school;

List all collections in a database:

show collections;

Drop a collection:

db.students.drop();

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Summary

MongoDB’s flexibility and simplicity make it a great choice for beginners and professionals alike. Start by mastering basic CRUD operations, then explore the powerful Aggregation Framework for advanced queries.😊

References:

https://www.infoq.com/articles/Starting-With-MongoDB/

https://www.w3schools.com/mongodb/

https://www.geeksforgeeks.org/mongodb-tutorial/

https://www.mongodb.com/resources/products/fundamentals/basics

https://www.tutorialspoint.com/mongodb/index.htm

https://www.youtube.com/watch?v=c2M-rlkkT5o