MongoDB is a powerful, flexible database solution that allows for scalable data storage, making it popular for applications requiring a robust NoSQL database. This cheat sheet compiles key commands, structures, and examples to streamline your workflow.

1. Getting Started with MongoDB

Installation

To begin using MongoDB, follow these steps for installation:

For macOS:

brew tap mongodb/brew
brew install mongodb-community

For Ubuntu:

sudo apt update
sudo apt install -y mongodb

Starting the MongoDB Service

To start your MongoDB server, use the following command:

mongod

This launches your MongoDB server process. You can access the database from another terminal with:

mongo

2. Basic Commands

Checking the Database

To view your current databases:

show dbs

Creating a Database

To create a new database, you can use the use command:

use myDatabase

This command switches to myDatabase, creating it if it doesn’t exist.

Drop a Database

To delete a database permanently:

db.dropDatabase()

3. Collections

Create a Collection

Use the following command to create a collection:

db.createCollection('myCollection')

Drop a Collection

To remove an existing collection:

db.myCollection.drop()

List Collections

To see all collections in your current database:

show collections

4. CRUD Operations

Create (Insert Data)

Insert One Document

To insert a single document into a collection:

db.myCollection.insertOne({ name: "John Doe", age: 30 })

Insert Multiple Documents

To insert multiple records at once:

db.myCollection.insertMany([
    { name: "Jane Doe", age: 25 },
    { name: "Mike Smith", age: 35 }
])

Read (Query Data)

Find One Document

To retrieve a single document:

db.myCollection.findOne({ name: "John Doe" })

Find All Documents

To retrieve all documents in a collection:

db.myCollection.find()

Query with Conditions

You can filter results using conditions:

db.myCollection.find({ age: { $gte: 30 } })

This will find all documents where age is greater than or equal to 30.

Update (Modify Data)

Update One Document

To update a single document:

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

Update Multiple Documents

To update multiple documents matching a condition:

db.myCollection.updateMany(
    { age: { $lt: 30 } },
    { $set: { status: "young" } }
)

Delete (Remove Data)

Delete One Document

To delete a single document:

db.myCollection.deleteOne({ name: "John Doe" })

Delete Multiple Documents

To delete multiple documents:

db.myCollection.deleteMany({ age: { $lt: 30 } })

5. Indexing

Create an Index

Indexes improve query performance. To create one, use:

db.myCollection.createIndex({ name: 1 })

This creates an ascending index on the name field.

List Indexes

To view all indexes on a collection:

db.myCollection.getIndexes()

6. Aggregation Framework

The aggregation framework allows you to perform complex data processing tasks.

Basic Aggregation

To combine data from documents:

db.myCollection.aggregate([
    { $match: { age: { $gte: 30 } } },
    { $group: { _id: "$name", averageAge: { $avg: "$age" } } }
])

7. Backup and Restore

Backup Data

To create a backup of your database:

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

Restore Data

To restore your database from a backup:

mongorestore /path/to/backup

8. Security

Create a User

To add a user with read and write permissions:

db.createUser({
    user: "myUser",
    pwd: "myPassword",
    roles: [{ role: "readWrite", db: "myDatabase" }]
})

Authentication

To require users to log in, start the server with:

mongod --auth

With this cheat sheet, you can quickly refer to essential MongoDB commands and concepts while developing your applications. Keep this handy as you navigate the powerful features that MongoDB offers!