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. 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 Show available databases: show dbs Show the currently selected database: db 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. 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. 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" }) 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") 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 } } ]) 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") 8. Backup and Restore Backup a Database mongodump --db myDatabase --out /backup/ Restore a Database mongorestore --db myDatabase /backup/myDatabase/ 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.ex

Feb 16, 2025 - 22:13

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.

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

Show available databases:

  show dbs

Show the currently selected database:

db

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.

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.

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" })

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")

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 } }
  ])

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")

8. Backup and Restore

Backup a Database

mongodump --db myDatabase --out /backup/

Restore a Database

mongorestore --db myDatabase /backup/myDatabase/

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")

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

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!