MongoDB: NOSQL Database Learning

1. brew services start mongodb/brew/mongodb-community

   
   

2. Verify the installation: Check if MongoDB is running:

   bash

   Copyps aux | grep mongod

   
   

3. Stop MongoDB: To stop MongoDB, use:

   bash

   Copybrew services stop mongodb/brew/mongodb-community

   
   

For Windows

1. Download MongoDB: Go to the MongoDB Download Center and download the installer for your version of Windows.

2. Run the Installer: Once the installer is downloaded, run it. Choose the Complete installation type. You can also choose to install MongoDB as a service, which will automatically start MongoDB when your system starts.

3. Configure MongoDB (Optional): You can configure the directory where MongoDB stores its data. By default, it’s stored in C:\data\db. If you want to change the location, you can modify it in the mongod.cfg configuration file.

4. Start MongoDB: After installation, MongoDB will start automatically if you opted to install it as a service. You can manually start it using the command:

   Copymongod --dbpath C:\data\db

   
   

5. Access MongoDB: To connect to the MongoDB server, open another command prompt window and type:

   mongo

1. Download MongoDB Shell:

   • Go to the MongoDB Download Center and download the latest version of MongoDB Shell for Windows (available as a .zip archive).

2. Extract the Downloaded Files: Extract the downloaded .zip archive to a directory, such as C:\mongodb-shell.

3. Add MongoDB Shell to PATH (Optional):

   • Add the directory where MongoDB Shell is extracted to the system’s PATH variable so that you can run it from any command prompt:

     • Right-click This PC > Properties > Advanced system settings > Environment Variables.

     • Under System Variables, find and select Path, then click Edit.

     • Add the path to the MongoDB Shell directory (e.g., C:\mongodb-shell).

4. Verify Installation: Open the command prompt and check the mongo shell version:

   mongo --version

   
   

1. Start MongoDB Shell

First, make sure MongoDB is running and then open the MongoDB shell by typing the following command in your terminal:

mongo

If MongoDB is running locally on the default port, it should automatically connect to the test database. If you’re connecting to a remote server, you can use this command:

mongo <hostname>:<port>

2. Create a Database

To create a new database, use the use command. MongoDB does not actually create the database until you insert some data into it. Here’s how you create and switch to a new database:

javascript

use myNewDatabase

This switches to the myNewDatabase database. If it doesn’t already exist, MongoDB will create it once you insert some data into it.

3. Create a Collection

Collections are automatically created when you insert documents into them. You can also explicitly create a collection using the db.createCollection() method.

Method 1: Insert a Document (Implicitly Creates Collection)

To create a collection, simply insert a document into the collection. Here’s an example:

javascript

db.myCollection.insertOne({

  name: "John",

  age: 30,

  city: "New York"

})

1. insertOne(): Inserts a single document into a collection.

2. insertMany(): Inserts multiple documents into a collection.

Let's say we want to update the age of a user named "Alice" to 26:

javascript

db.myCollection.updateOne(

  { name: "Alice" }, // filter: find the document where name is Alice

  { $set: { age: 26 } } // update: set the age field to 26

)

• Explanation:

  • { name: "Alice" }: This is the filter, which selects the document to be updated.

  • { $set: { age: 26 } }: The $set operator is used to update the value of the age field to 26.

2. Update Multiple Documents

If you want to update multiple documents, you can use the updateMany() method. This updates all documents that match the filter criteria.

Syntax:

javascript

db.collection.updateMany(

  { <filter> },

  { <update> },

  { <options> }

)

Example:

Let's say you want to update the city field to "San Francisco" for all users who are older than 30:

javascript

db.myCollection.updateMany(

  { age: { $gt: 30 } }, // filter: find documents where age is greater than 30

  { $set: { city: "San Francisco" } } // update: set city to San Francisco

)

• Explanation:

  • { age: { $gt: 30 } }: This filter finds all documents where the age is greater than 30.

  • { $set: { city: "San Francisco" } }: This updates the city field for all matched documents.