NodeJs MongoDB Collection

Last modified on: October 19, 2024

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<h3>Working with Collections in MongoDB</h3>
<p>In MongoDB, a collection is a group of documents that are stored in the database. Collections are analogous to tables in relational databases but are more flexible since they can store documents of varying structures. This guide will cover how to create, read, update, and delete collections in MongoDB.</p>
<hr />
<h3>1. Creating a Collection</h3>
<h4>Using MongoDB Shell</h4>
<p>To create a collection in the MongoDB shell:</p>
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<p><strong>Open the MongoDB Shell</strong>:</p>
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<pre class="language-javascript"><code>mongo
</code></pre>
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<p><strong>Switch to the Database</strong>: Choose the database where you want to create the collection:</p>
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<pre class="language-javascript"><code>use mydatabase
</code></pre>
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<div class="flex items-center text-token-text-secondary bg-token-main-surface-secondary px-4 py-2 text-xs font-sans justify-between rounded-t-md h-9"><strong>Create a Collection</strong>: You can create a collection using the <code>createCollection</code> method:</div>
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<pre class="language-javascript"><code>db.createCollection('users')
</code></pre>
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<p>You can also create a collection simply by inserting a document into a non-existing collection:</p>
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<pre class="language-javascript"><code>db.users.insertOne({ name: 'Alice', email: 'alice@example.com' })
</code></pre>
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<p>This command will create the <code>users</code> collection if it doesn't already exist.</p>
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<h3>2. Reading from a Collection</h3>
<p>To retrieve documents from a collection, use the <code>find</code> method.</p>
<h4>Using MongoDB Shell</h4>
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<p><strong>Retrieve All Documents</strong>:</p>
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<pre class="language-javascript"><code>db.users.find()
</code></pre>
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<p><strong>Retrieve Documents with a Query</strong>:</p>
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<pre class="language-javascript"><code>db.users.find({ name: 'Alice' })
</code></pre>
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<p><strong>Pretty Print the Output</strong>:</p>
<p>To format the output nicely, use:</p>
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<pre class="language-javascript"><code>db.users.find().pretty()
</code></pre>
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<h3>3. Updating a Collection</h3>
<p>To update documents within a collection, use the <code>updateOne</code>, <code>updateMany</code>, or <code>replaceOne</code> methods.</p>
<h4>Using MongoDB Shell</h4>
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<p><strong>Update a Single Document</strong>:</p>
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<pre class="language-javascript"><code>db.users.updateOne(
    { name: 'Alice' }, // Filter
    { $set: { email: 'alice.new@example.com' } } // Update
)
</code></pre>
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<p><strong>Update Multiple Documents</strong>:</p>
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<pre class="language-javascript"><code>db.users.updateMany(
    { name: 'Alice' }, // Filter
    { $set: { status: 'active' } } // Update
)
</code></pre>
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<h3>4. Deleting from a Collection</h3>
<p>To remove documents from a collection, use the <code>deleteOne</code> or <code>deleteMany</code> methods.</p>
<h4>Using MongoDB Shell</h4>
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<li>
<p><strong>Delete a Single Document</strong>:</p>
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<pre class="language-javascript"><code>db.users.deleteOne({ name: 'Alice' })
</code></pre>
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<p><strong>Delete Multiple Documents</strong>:</p>
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<pre class="language-javascript"><code>db.users.deleteMany({ status: 'inactive' })
</code></pre>
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<h3>5. Counting Documents in a Collection</h3>
<p>To count the number of documents in a collection, use the <code>countDocuments</code> method.</p>
<h4>Using MongoDB Shell</h4>
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<pre class="language-javascript"><code>db.users.countDocuments()
</code></pre>
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<h3>6. Indexing a Collection</h3>
<p>Creating indexes on collections can improve query performance. Use the <code>createIndex</code> method to create an index.</p>
<h4>Using MongoDB Shell</h4>
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<pre class="language-javascript"><code>db.users.createIndex({ email: 1 }) // Creates an ascending index on the email field
</code></pre>
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<h3>7. Integrating with Node.js</h3>
<p>To work with collections programmatically in a Node.js application, follow these steps:</p>
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<p><strong>Set Up a Node.js Project</strong>: If you haven't done so, create a new project and install the MongoDB driver:</p>
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<pre class="language-javascript"><code>mkdir my-node-mongodb-app
cd my-node-mongodb-app
npm init -y
npm install mongodb
</code></pre>
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<p><strong>Create <code>app.js</code></strong>:</p>
<p>Create a file named <code>app.js</code>:</p>
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<pre class="language-javascript"><code>touch app.js
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<p><strong>Add Code to <code>app.js</code></strong>:</p>
<p>Open <code>app.js</code> and add the following code to demonstrate creating and interacting with a collection:</p>
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<pre class="language-javascript"><code>const { MongoClient } = require('mongodb');

const uri = 'mongodb://localhost:27017'; // Replace with your MongoDB URI
const client = new MongoClient(uri);

async function run() {
    try {
        await client.connect();
        const database = client.db('mydatabase');
        const collection = database.collection('users');

// Create a collection
        await collection.insertOne({ name: 'Alice', email: 'alice@example.com' });
        console.log('Document inserted.');

// Read documents
        const users = await collection.find().toArray();
        console.log('Users:', users);

// Update a document
        await collection.updateOne({ name: 'Alice' }, { $set: { email: 'alice.new@example.com' } });
        console.log('Document updated.');

// Delete a document
        await collection.deleteOne({ name: 'Alice' });
        console.log('Document deleted.');
        
    } catch (error) {
        console.error('Error:', error);
    } finally {
        await client.close();
    }
}

run().catch(console.error);
</code></pre>
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<p><strong>Run the Application</strong>:</p>
<p>Execute the following command to run your application:</p>
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<pre class="language-javascript"><code>node app.js
</code></pre>
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<p>You should see console logs indicating the document was inserted, updated, and deleted.</p>
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<h3>Conclusion</h3>
<p>Working with collections in MongoDB is a fundamental aspect of using the database. You can create, read, update, and delete documents easily, allowing for flexible data management. With the integration of Node.js, you can build powerful applications that leverage MongoDB's capabilities.</p>
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