MongoDB is a popular NoSQL database that stores data in a flexible, JSON-like format known as BSON (Binary JSON). It is designed to handle large volumes of unstructured and semi-structured data, making it an ideal choice for modern web applications. This tutorial will guide you through the basic operations and features of MongoDB.

1. Setting Up MongoDB

Before diving into MongoDB operations, you need to install MongoDB. Follow these steps based on your system:

• For Windows: Download MongoDB from the official MongoDB download page. Follow the installation instructions.
• For macOS: You can use Homebrew to install MongoDB:

  bash
  brew tap mongodb/brewbrew install mongodb-community@6.0
  

• For Linux: MongoDB can be installed via package managers like apt or yum. Instructions are available on the MongoDB documentation.

Once installed, run MongoDB as a service:

bash
mongod

2. MongoDB Basics

Starting MongoDB

To interact with MongoDB, use the mongo shell or a MongoDB client (e.g., Compass, Node.js, etc.). Open a terminal window and type:

bash
mongo

This opens an interactive MongoDB shell where you can execute queries and commands.

Database Operations

2.1. Create and Switch Databases

MongoDB creates databases automatically when you insert data into them. To switch to a specific database:

javascript
use myDatabase

If myDatabase does not exist, MongoDB will create it once you insert data into a collection.

2.2. Show Databases

To list all available databases:

javascrip
show databases

3. Collections and Documents

MongoDB stores data in collections, which are similar to tables in relational databases. Each collection contains multiple documents, which are analogous to rows in relational databases. Documents in MongoDB are stored as BSON objects.

3.1. Create a Collection

To create a collection, use the following command:

javascript
db.createCollection("myCollection")

This is not strictly necessary, as collections are automatically created when data is inserted into them.

3.2. Show Collections

To view all collections in the current database:

javascript
show collections

3.3. Insert Documents

You can insert documents into a collection using insertOne() (for a single document) or insertMany() (for multiple documents).

Insert One Document:

javascript
db.myCollection.insertOne({ name: "Alice", age: 30, city: "New York" })

Insert Multiple Documents:

javascript
db.myCollection.insertMany([  { name: "Bob", age: 25, city: "San Francisco" },  { name: "Charlie", age: 35, city: "Los Angeles" }])

3.4. View Documents

To retrieve all documents from a collection, use the find() method:

javascript
db.myCollection.find()

You can use pretty() to format the output:

javascript
db.myCollection.find().pretty()

To filter documents, pass a query object to the find() method:

javascript
db.myCollection.find({ age: { $gt: 25 } })

This will return documents where the age field is greater than 25.

4. Updating Documents

You can update documents using the updateOne(), updateMany(), and replaceOne() methods.

4.1. Update a Single Document

To update a single document, use updateOne():

javascript
db.myCollection.updateOne(  { name: "Alice" },  { $set: { age: 31 } })

This updates the first document that matches the query (where name is "Alice") and sets the age field to 31.

4.2. Update Multiple Documents

To update multiple documents, use updateMany():

javascript
db.myCollection.updateMany(  { city: "New York" },  { $set: { city: "Los Angeles" } })

This updates all documents where city is "New York" and changes it to "Los Angeles."

4.3. Replace a Document

To replace a document entirely, use replaceOne():

javascript
db.myCollection.replaceOne(  { name: "Bob" },  { name: "Robert", age: 26, city: "San Francisco" })

5. Deleting Documents

You can delete documents using deleteOne() and deleteMany().

5.1. Delete a Single Document

To delete a single document:

javascript
db.myCollection.deleteOne({ name: "Charlie" })

5.2. Delete Multiple Documents

To delete multiple documents that match a condition:

javascript
db.myCollection.deleteMany({ city: "Los Angeles" })

6. Query Operators in MongoDB

MongoDB provides various query operators to help you filter and search for documents. Some common operators include:

• $gt: Greater than.

  javascript
  db.myCollection.find({ age: { $gt: 25 } })
  

• $lt: Less than.

  javascript
  db.myCollection.find({ age: { $lt: 35 } })
  

• $in: Matches any value in an array.

  javascript
  db.myCollection.find({ age: { $in: [25, 30] } })
  

• $regex: Regular expression match.

  javascript
  db.myCollection.find({ name: { $regex: "^A" } })
  

• $and, $or: Logical operators to combine conditions.

  javascript
  db.myCollection.find({ $and: [{ age: { $gt: 20 } }, { city: "New York" }] })
  

• $exists: Matches documents with a specific field.

  javascript
  db.myCollection.find({ email: { $exists: true } })
  

7. Indexing in MongoDB

Indexes in MongoDB improve the speed of search queries. By default, MongoDB creates an index on the _id field of each collection.

7.1. Create an Index

To create an index on a field:

javascript
db.myCollection.createIndex({ name: 1 }) // Ascending order index

To create a descending index:

javascript
db.myCollection.createIndex({ age: -1 }) // Descending order index

7.2. List Indexes

To view all indexes in a collection:

javascript
db.myCollection.getIndexes()

8. Aggregation in MongoDB

Aggregation in MongoDB is used to process and analyze data. You can use the aggregation pipeline to perform complex data transformations.

8.1. Basic Aggregation Example

To aggregate documents:

javascript
db.myCollection.aggregate([  { $match: { city: "New York" } },  { $group: { _id: "$age", total: { $sum: 1 } } }])

In this example, the aggregation pipeline:

1. $match: Filters documents where the city is "New York".
2. $group: Groups the documents by age and calculates the total count of documents for each age.

9. Backup and Restore in MongoDB

You can back up and restore data using MongoDB's built-in tools.

9.1. Backup Database

Use mongodump to back up a database:

bash
mongodump --db=myDatabase --out=/path/to/backup

9.2. Restore Database

To restore a database, use mongorestore:

bash
mongorestore --db=myDatabase /path/to/backup/myDatabase

10. Conclusion

This MongoDB tutorial covered the basic operations such as creating databases and collections, inserting, updating, and deleting documents, using query operators, indexing, and aggregation. MongoDB's flexibility allows you to model your data in a way that is more suited to your application's needs.

For more advanced features and topics such as transactions, replica sets, and sharding, refer to the official MongoDB documentation.