MongoDB Commands Categorized

The Ultimate List of MongoDB Commands Categorized by Usage

MongoDB is a powerful NoSQL database known for its flexibility and scalability. Whether you are a beginner or an advanced user, mastering MongoDB commands will help you efficiently manage databases, collections, and documents. This guide categorizes MongoDB commands based on their usage, covering everything from basic operations to advanced database management.

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1. Basic MongoDB Commands

Starting and Stopping MongoDB

• Start MongoDB:

  sudo systemctl start mongod

• Stop MongoDB:

  sudo systemctl stop mongod

• Restart MongoDB:

  sudo systemctl restart mongod

• Check MongoDB status:

  sudo systemctl status mongod

Connecting to MongoDB

• Open MongoDB shell:

  mongo

• Connect to a specific database:

  use <database_name>

• Show available databases:

  show dbs

• Show the currently selected database:

  db

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2. Database Management

Creating a Database

MongoDB automatically creates a database when a document is inserted. However, you can explicitly select a database:

use myDatabase

(This does not create the database until data is added.)

Dropping a Database

db.dropDatabase()

Deletes the currently selected database.

Listing All Databases

show dbs

Displays all available databases.

Checking the Current Database

db

Displays the name of the currently selected database.

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3. Collection Management

Creating a Collection

db.createCollection("myCollection")

Creates an empty collection.

Listing All Collections

show collections

Displays all collections in the current database.

Dropping a Collection

db.myCollection.drop()

Deletes a specific collection.

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4. Document Management (CRUD Operations)

Inserting Documents

• Insert a single document:

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

• Insert multiple documents:

  db.myCollection.insertMany([
      { name: "Bob", age: 30, city: "Los Angeles" },
      { name: "Charlie", age: 35, city: "Chicago" }
  ])

Reading Documents (Querying)

• Find all documents in a collection:

  db.myCollection.find()

• Find a specific document:

  db.myCollection.findOne({ name: "Alice" })

• Find documents with specific conditions:

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

Finds all documents where age is greater than 30.

• Projection (return only specific fields):

  db.myCollection.find({ }, { name: 1, _id: 0 })

Returns only the name field and excludes _id.

Updating Documents

• Update a single document:

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

• Update multiple documents:

  db.myCollection.updateMany(
      { city: "New York" },
      { $set: { country: "USA" } }
  )

• Replace a document:

  db.myCollection.replaceOne(
      { name: "Alice" },
      { name: "Alice", age: 27, city: "Boston" }
  )

Deleting Documents

• Delete a single document:

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

• Delete multiple documents:

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

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5. Indexing and Performance Optimization

Creating Indexes

• Create an index on a field:

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

• Create a compound index:

  db.myCollection.createIndex({ name: 1, age: -1 })

• Create a unique index:

  db.myCollection.createIndex({ email: 1 }, { unique: true })

Listing Indexes

db.myCollection.getIndexes()

Dropping an Index

db.myCollection.dropIndex("name_1")

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6. Aggregation Framework

Using Aggregation Pipelines

• Count documents in a collection:

  db.myCollection.countDocuments()

• Group and count by a field:

  db.myCollection.aggregate([
      { $group: { _id: "$city", count: { $sum: 1 } } }
  ])

• Sort documents:

  db.myCollection.aggregate([
      { $sort: { age: -1 } }
  ])

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7. User and Role Management

Creating a User

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

Listing Users

db.getUsers()

Deleting a User

db.dropUser("adminUser")

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8. Backup and Restore

Backup a Database

mongodump --db myDatabase --out /backup/

Restore a Database

mongorestore --db myDatabase /backup/myDatabase/

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9. Replica Sets and Sharding

Checking Replica Set Status

rs.status()

Initiating a Replica Set

rs.initiate()

Adding a Member to a Replica Set

rs.add("mongodb2.example.com:27017")

Sharding a Collection

sh.enableSharding("myDatabase")

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10. Server Administration and Monitoring

Checking MongoDB Server Status

db.serverStatus()

Checking Database Stats

db.stats()

Checking Collection Stats

db.myCollection.stats()

Logging Slow Queries

db.setProfilingLevel(1)

Enabling Authorization

Edit /etc/mongod.conf and add:

security:
  authorization: enabled

Restart MongoDB:

sudo systemctl restart mongod

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Conclusion

This guide provides a categorized reference for essential MongoDB commands. Whether you are working with collections, queries, indexes, or replication, these commands will help you efficiently manage MongoDB databases. Keep this guide handy as a quick reference! 🚀