MongoDB Shell Commands - A Comprehensive Guide

Step 1: Start MongoDB Shell

1. Open your terminal.

2. Run the mongo command to start the MongoDB shell:
   

mongo

Step 2: Switch to a Database

1. To switch to a specific database, use the use command followed by the name of the database:

use mydatabase

Replace mydatabase with the name of your database.

Step 3: Show Databases

1. To show all databases available on the MongoDB server, run the following command:

show databases

This command will list all databases, including empty databases.

Step 4: Show Collections

1. After switching to a database, you can list all collections within that database using the show collections command:

show collections

This command will display all collections present in the current database.

Step 5: Show Data from a Collection

1. To display all documents (data) in a collection, use the db.collectionName.find() method. Replace collectionName with the name of your collection:

db.collectionName.find()

For example, to display all documents in a collection named users:

db.users.find()

1. You can also apply query criteria to filter the results. For example, to find documents where the age field is greater than 18:

db.collectionName.find({ age: { $gt: 18 } })

Step 6: Insert Documents into a Collection

1. To insert documents into a collection, use the db.collectionName.insertOne() or db.collectionName.insertMany() methods.

For example, to insert a single document into a collection named users:

db.users.insertOne({ name: "John", age: 30 })

1. To insert multiple documents into a collection:

db.users.insertMany([
    { name: "Alice", age: 25 },
    { name: "Bob", age: 35 }
])

Step 7: Update Documents in a Collection

1. To update documents in a collection, use the db.collectionName.updateOne() or db.collectionName.updateMany() methods.

For example, to update a single document in the users collection:

db.users.updateOne({ name: "John" }, { $set: { age: 31 } })

1. To update multiple documents:

db.users.updateMany({ age: { $lt: 30 } }, { $set: { category: "Young" } })

Step 8: Delete Documents from a Collection

1. To delete documents from a collection, use the db.collectionName.deleteOne() or db.collectionName.deleteMany() methods.

For example, to delete a single document from the users collection:

db.users.deleteOne({ name: "John" })

1. To delete multiple documents:

db.users.deleteMany({ category: "Young" })

Step 9: Exit MongoDB Shell

1. To exit the MongoDB shell, type exit and press Enter:

exit

These commands cover the basic CRUD operations (Create, Read, Update, Delete) in MongoDB from the shell. Adjust the database, collection names, and query criteria as needed for your specific use case.