A Complete Guide - Using Mongo Shell and MongoDB Atlas

1. How do I connect to a MongoDB Atlas cluster using the Mongo Shell?

Answer:
To connect to a MongoDB Atlas cluster using the Mongo Shell, you'll need to ensure you have a connection string from your Atlas dashboard. Here's a step-by-step guide:

1. Get the Connection String: Navigate to your MongoDB Atlas project, go to "Connect," select "Connect your application," and choose "Mongo Shell."
2. Copy the Connection String: Replace <password> in the connection string with your user password.
3. Open a Terminal or Command Prompt: Run the copied string to establish a connection.

Example:

mongo "mongodb+srv://<username>:<password>@mycluster.mongodb.net/mydatabase?retryWrites=true&w=majority"

2. How do I insert documents into a collection using the Mongo Shell?

Answer:
Use the insertOne() or insertMany() methods to insert documents into a collection.

Example with insertOne():

db.myCollection.insertOne({ name: "Alice", age: 25, email: "alice@example.com"
})

Example with insertMany():

db.myCollection.insertMany([ { name: "Bob", age: 30, email: "bob@example.com" }, { name: "Charlie", age: 35, email: "charlie@example.com" }
])

3. How can I query documents from a collection in MongoDB Atlas using the Mongo Shell?

Answer:
Use the find() method to query documents. You can pass a query object to filter results.

Example (finding all documents):

db.myCollection.find({}).pretty()

Example (finding documents by a specific field):

db.myCollection.find({ age: 30 }).pretty()

Example (finding documents with conditions):

db.myCollection.find({ age: { $gt: 25 } }).pretty() // Age greater than 25

4. How do I update documents in a collection using the Mongo Shell?

Answer:
Use the updateOne() or updateMany() methods to update documents.

Example with updateOne():

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

Example with updateMany():

db.myCollection.updateMany( { age: { $lt: 30 } }, { $inc: { age: 1 } } // Increment age by 1
)

5. How can I delete documents from a collection in MongoDB Atlas using the Mongo Shell?

Answer:
Use the deleteOne() or deleteMany() methods to delete documents.

Example with deleteOne():

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

Example with deleteMany():

db.myCollection.deleteMany({ age: { $gt: 25 } })

6. How do I create an index on a collection in MongoDB Atlas using the Mongo Shell?

Answer:
Use the createIndex() method to improve query performance by creating an index on one or more fields.

Example (single-field index):

db.myCollection.createIndex({ age: 1 }) // 1 for ascending, -1 for descending

Example (compound index):

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

7. How can I check the list of collections in my MongoDB Atlas database using the Mongo Shell?

Answer:
Use the show collections command to list all collections in the current database.

Example:

show collections

8. How do I aggregate data in MongoDB Atlas using the Mongo Shell?

Answer:
Use the aggregate() method to process data records and return computed results.

Example (summing ages of all users):

db.myCollection.aggregate([ { $group: { _id: null, totalAge: { $sum: "$age" } } }
])

Example (grouping by age and counting users):

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

9. How can I create a new database in MongoDB Atlas using the Mongo Shell?

Answer:
Switch to a new database using the use command. If the database does not exist, MongoDB will create it upon the first insertion of a document.

Example:

use myNewDatabase
db.createCollection("myCollection") // This creates the database if it doesn't exist

Adding a document to create the database immediately:

use myNewDatabase
db.myCollection.insertOne({ name: "NewUser", age: 40 })

10. How can I view the performance statistics and indexes in MongoDB Atlas?

Answer:
While viewing performance statistics and indexes is typically done via the MongoDB Atlas web interface, you can also use the Mongo Shell to check for indexes.

Viewing Indexes:

db.myCollection.getIndexes()

For Performance Statistics:

1. Connect to the Atlas Cluster.
2. Use the db.currentOp() command to view current operations and their performance details.
3. Check the Atlas Dashboard for more comprehensive performance monitoring, including metrics like CPU usage, memory usage, and read/write operations.

Example: