MongoDB Shell

MongoDB Shell

MongoDB Shell is a powerful command-line interface that allows users to interact with MongoDB databases. It provides a way to perform various database operations, including querying, updating, inserting, and deleting data. The MongoDB Shell is based on JavaScript, which makes it easy for developers to work with the database using familiar syntax.

Connecting to MongoDB

To start using the MongoDB Shell, you need to connect to a MongoDB database. The basic syntax to connect is as follows:

bash
mongo <connection-string>

• <connection-string>: This is the URI to connect to the MongoDB server. It includes details like server address, port, and authentication credentials (if required).

Example:

bash
mongo mongodb://localhost:27017/mydatabase

Basic Commands

1. Show Databases

To list all available databases, you can use the show dbs command.

javascript
> show dbs
admin       0.000GB
mydatabase  0.003GB
local       0.000GB

2. Switch Database

To switch to a specific database, use the use command.

javascript
> use mydatabase
switched to db mydatabase

3. Show Collections

To list all collections within the current database, use the show collections command.

javascript
> show collections
users
products

CRUD Operations

1. Insert Documents

To insert documents into a collection, use the insertOne or insertMany methods.

javascript
> db.users.insertOne({ name: "John Doe", age: 30, email: "john@example.com" })

2. Query Documents

To retrieve data from a collection, use the find method.

javascript
> db.users.find({ age: { $gt: 25 } })

3. Update Documents

To update documents, use the updateOne or updateMany methods.

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

4. Delete Documents

To delete documents, use the deleteOne or deleteMany methods.

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

Aggregation

MongoDB Shell supports aggregation operations for more complex data processing.

javascript
> db.orders.aggregate([
    { $match: { status: "completed" } },
    { $group: { _id: "$customer", total: { $sum: "$amount" } } }
])

This example uses aggregation to calculate the total amount spent by each customer for completed orders.

Indexing

Creating indexes can significantly improve query performance.

javascript
> db.users.createIndex({ name: 1 })

This creates an ascending index on the "name" field in the "users" collection.

Conclusion

MongoDB Shell is a versatile tool that enables developers to interact with MongoDB databases efficiently. It supports various CRUD operations, aggregation, indexing, and more, making it a fundamental part of working with MongoDB. With its easy-to-understand JavaScript-based syntax, developers can quickly manage and query their data using the MongoDB Shell.