CRUD Operations in MongoDB

1. Introduction

CRUD operations are the four basic functions of persistent storage. In MongoDB, which is a NoSQL database, these operations allow you to Create, Read, Update, and Delete documents in your collections.

2. CRUD Overview

The basic operations can be summarized as follows:

Create: Inserting new documents into collections.
Read: Retrieving documents from collections.
Update: Modifying existing documents.
Delete: Removing documents from collections.

3. Create Operation

To create a new document in a MongoDB collection, you use the insertOne() or insertMany() methods.

const { MongoClient } = require('mongodb');

async function run() {
    const client = new MongoClient('mongodb://localhost:27017');
    await client.connect();
    const database = client.db('sampleDB');
    const collection = database.collection('users');

    // Insert a single document
    const singleUser = { name: "John Doe", age: 25 };
    const result = await collection.insertOne(singleUser);
    console.log(`A document was inserted with the _id: ${result.insertedId}`);

    // Insert multiple documents
    const multipleUsers = [
        { name: "Alice", age: 30 },
        { name: "Bob", age: 22 }
    ];
    const insertManyResult = await collection.insertMany(multipleUsers);
    console.log(`${insertManyResult.insertedCount} documents were inserted.`);
}

run().catch(console.dir);

4. Read Operation

To read documents from a MongoDB collection, you can use the find() method which returns a cursor to the documents in the collection.

async function readDocuments() {
    const cursor = collection.find();
    await cursor.forEach(doc => console.log(doc));
}

5. Update Operation

Updating documents can be done using the updateOne() or updateMany() methods.

async function updateDocument() {
    const updateResult = await collection.updateOne(
        { name: "John Doe" },
        { $set: { age: 26 } }
    );
    console.log(`${updateResult.modifiedCount} document(s) was/were updated.`);
}

6. Delete Operation

To delete documents, you can use the deleteOne() or deleteMany() methods.

async function deleteDocument() {
    const deleteResult = await collection.deleteOne({ name: "John Doe" });
    console.log(`${deleteResult.deletedCount} document(s) was/were deleted.`);
}

7. Best Practices

When performing CRUD operations in MongoDB, consider the following best practices:

Always validate input data before performing operations.
Use indexes to improve read performance.
Handle errors and exceptions gracefully.
Monitor the performance of your queries.

8. FAQ

What is the difference between insertOne() and insertMany()?

insertOne() is used to insert a single document while insertMany() is used to insert multiple documents in one operation.

Can I update multiple documents at once?

Yes, you can use the updateMany() method to update multiple documents that match a specified filter.

What happens if I try to delete a document that does not exist?

If you attempt to delete a document that does not exist, MongoDB will not throw an error. The result will indicate that no documents were deleted.