MongoDB class 3

Introduction to MongoDB::

Document Database:
A record in MongoDB is a document, which is a data structure composed of field 
and value pairs. MongoDB documents are similar to JSON objects. The values of 
fields may include other documents, arrays, and arrays of documents.

A MongoDB document:
{
_id:xxxxxxxxxxx,
key:value,
key:value,
key:value
}

The advantages of using documents are:

1)Documents correspond to native data types in many programming languages.
2)Embedded documents and arrays reduce need for expensive joins.
3)Dynamic schema supports fluent polymorphism.


>mongod ----->   to start the mongodb service from cmd 
>ctrl+c   ----->   to stop the mongodb service.

>mongosh ----->  to start the mongo shell from cmd
>ctrl+c   --->  to stop the mongo shell.

Commonly used datatypes in mongodb :

1.String 
2.Integer 
3.Boolean 
4.Double
5.Arrays
6.Object(for passing nested object)
7.Null
8.Date (to store the date time)


Here's a comprehensive guide on MongoDB, covering concepts, differences with RDBMS, installation, and basic operations:



 1. What is MongoDB?



- MongoDB is a NoSQL, document-oriented database that stores data in JSON-like, flexible documents. This allows for dynamic schemas, meaning you can store and query data without needing to define the structure in advance.



 2. Difference between MongoDB and RDBMS



| Feature                    | MongoDB                                             | RDBMS (Relational Database Management System)             |

|----------------------------|----------------------------------------------------|------------------------------------------------------------|

| Data Storage           | JSON-like documents (BSON)                          | Tables with rows and columns                                |

| Schema                 | Dynamic, schema-less                               | Fixed schema with predefined structure                      |

| Joins                  | No joins; data is often embedded                    | Supports joins across multiple tables                       |

| Scalability            | Horizontally scalable (sharding)                    | Vertically scalable (increasing resources on a single server)|

| Flexibility            | High, allows for different document structures      | Rigid, requires schema changes to accommodate new data types |

| Transactions           | Supports multi-document ACID transactions          | Supports ACID transactions                                  |

| Data Relationships     | Typically handled using embedded documents or references | Handled through foreign keys and joins                       |

| Use Cases              | Ideal for hierarchical data, real-time analytics, big data | Suitable for complex queries, financial systems              |



 3. Installing MongoDB

# MongoDB Driver Installation

- For Node.js, install the MongoDB driver using npm:

  npm install mongodb


# MongoDB Compass

- MongoDB Compass is a GUI tool that allows you to interact with your MongoDB databases visually.

- Download and Install: Visit [MongoDB Compass Download](https://www.mongodb.com/try/download/compass) and follow the installation instructions.



# MongoDB Shell (mongosh) Installation

- MongoDB Shell (mongosh) is a command-line tool that lets you interact with your MongoDB instance.

- Installation:

  - For most OS, MongoDB Shell comes with MongoDB installation.

  - You can also download it separately from the [MongoDB Shell Download](https://www.mongodb.com/try/download/shell) page.



 4. MongoDB Basic Operations

# Create a Database

- In MongoDB, databases are created automatically when you insert data into them.

use myDatabase



# Create a Collection

- Collections in MongoDB are equivalent to tables in RDBMS.

- Like databases, collections are created when you insert the first document.

db.createCollection("myCollection")


# Insert Documents

- Insert a Single Document:

  db.myCollection.insertOne({ name: "John", age: 25, city: "New York" })


- Insert Multiple Documents:

  db.myCollection.insertMany([

      { name: "Jane", age: 28, city: "Los Angeles" },

      { name: "Mike", age: 32, city: "Chicago" }

  ])

# Find Documents
- Find All Documents:

  db.myCollection.find()

  
- Find with a Condition:
  javascript

  db.myCollection.find({ age: 25 })


# Update Documents
- Update a Single Document:

  db.myCollection.updateOne({ name: "John" }, { $set: { age: 26 } })

 

- Update Multiple Documents:

  db.myCollection.updateMany({ city: "Chicago" }, { $set: { city: "Houston" } })

  
# Remove Documents
- Delete a Single Document:

  db.myCollection.deleteOne({ name: "Mike" })

  

- Delete Multiple Documents:

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

  


 5. MongoDB Shell Commands

- Show Databases:
  show dbs

- Switch to a Database:
  use myDatabase

- Show Collections in a Database:
  show collections

- Drop a Database:
  db.dropDatabase()

 
- Drop a Collection:
  db.myCollection.drop()

 

 Summary
- MongoDB is a flexible, schema-less NoSQL database that differs from traditional RDBMS systems in its data storage and scalability approach.

- You can interact with MongoDB through the MongoDB Shell, programmatically using drivers like the Node.js MongoDB driver, or visually through MongoDB Compass.

- MongoDB operations revolve around CRUD (Create, Read, Update, Delete) principles, which are executed on collections of documents.