MERNSTACK

MongoDB

a step-by-step guide to learning MongoDB with code examples:

  1. Installation: To get started with MongoDB, you need to install it. You can download and install the MongoDB Community Server from the official website. Once you have installed MongoDB, you can start the MongoDB server by running the following command in your terminal:
mongodb
  1. Creating a Database: In MongoDB, you can create a database using the use command. If the database does not exist, MongoDB will create it for you:
use mydatabase
  1. Creating a Collection: A collection is a group of related documents in MongoDB. You can create a collection using the db.createCollection() method:
db.createCollection('mycollection')
  1. Inserting Documents: You can insert a new document into a collection using the insertOne() method:
db.mycollection.insertOne({
  name: 'John Doe',
  age: 30,
  email: 'john.doe@example.com'
})

In this example, a new document with the fields name, age, and email is inserted into the mycollection collection.

  1. Querying Documents: You can query documents in a collection using the find() method:
db.mycollection.find()

This will return the first document in the mycollection collection where the name field is equal to “John Doe”.

  1. Updating Documents: You can update a document in a collection using the updateOne() method:
db.mycollection.updateOne(
  { name: 'John Doe' },
  { $set: { age: 35 } }
)

In this example, the document where the name field is equal to “John Doe” is updated to set the age field to 35.

  1. Deleting Documents: You can delete a document from a collection using the deleteOne() method:
db.mycollection.deleteOne({ name: 'John Doe' })

In this example, the document where the name field is equal to “John Doe” is deleted from the mycollection collection.

  1. Aggregation: Aggregation operations process data records and return computed results. You can use the aggregate() method to perform aggregation operations:
db.mycollection.aggregate([
  { $group: { _id: '$name', total: { $sum: '$age' } } }
])

In this example, the aggregate() method groups the documents in the mycollection collection by the name field and computes the total of the age field for each group.

  1. Indexes: Indexes can be used to improve query performance. You can create an index using the createIndex() method:
db.mycollection.createIndex({ name: 1 })

In this example, an index is created on the name field of the mycollection collection.

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