Node.js Database Access

Node.js Database Access

Introduction
Node.js is a popular JavaScript runtime that allows developers to build server-side applications. One of the essential aspects of any server-side application is the ability to access databases for data storage and retrieval. In this documentation, we will explore various methods for accessing databases in Node.js, along with code examples and explanations.

Table of Contents

1. Setting up a Database Connection
   1.1. Installing Database Drivers
   1.2. Connecting to the Database
   1.3. Handling Connection Errors

2. Performing CRUD Operations
   2.1. Creating Records
   2.2. Reading Records
   2.3. Updating Records
   2.4. Deleting Records

1. Setting up a Database Connection

1.1. Installing Database Drivers
To interact with databases in Node.js, we need appropriate database drivers. For example, for MongoDB, we can use the 'mongodb' driver, and for MySQL, we can use 'mysql' or 'mysql2.' To install these drivers, we can use the Node Package Manager (NPM).

bash
# Example for MongoDB
npm install mongodb

# Example for MySQL
npm install mysql

1.2. Connecting to the Database
After installing the appropriate driver, we need to establish a connection to the database. The connection typically requires providing credentials like the database URL, username, and password. The code below demonstrates how to connect to a MongoDB database using the 'mongodb' driver.

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

const uri = 'mongodb://localhost:27017/mydatabase';
const client = new MongoClient(uri);

async function connectToDatabase() {
  try {
    await client.connect();
    console.log('Connected to the database');
  } catch (err) {
    console.error('Error connecting to the database:', err);
  }
}

connectToDatabase();

1.3. Handling Connection Errors
It's crucial to handle connection errors gracefully. In case the database connection fails, we should implement appropriate error handling and retries.

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

const uri = 'mongodb://localhost:27017/mydatabase';
const client = new MongoClient(uri);

async function connectToDatabase() {
  try {
    await client.connect();
    console.log('Connected to the database');
  } catch (err) {
    console.error('Error connecting to the database:', err);
    // Handle the error here, e.g., retry the connection
  }
}

connectToDatabase();

2. Performing CRUD Operations

2.1. Creating Records
To insert data into the database, we use the appropriate methods provided by the database driver. For example, to add a document to a MongoDB collection, we can use the insertOne method.

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

const uri = 'mongodb://localhost:27017/mydatabase';
const client = new MongoClient(uri);

async function createRecord(data) {
  try {
    await client.connect();
    const collection = client.db().collection('mycollection');
    const result = await collection.insertOne(data);
    console.log('Inserted document with _id:', result.insertedId);
  } catch (err) {
    console.error('Error creating record:', err);
  }
}

const dataToInsert = { name: 'John Doe', age: 30, email: 'john@example.com' };
createRecord(dataToInsert);

2.2. Reading Records
To retrieve data from the database, we can use methods like find in MongoDB or SQL queries in relational databases.

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

const uri = 'mongodb://localhost:27017/mydatabase';
const client = new MongoClient(uri);

async function readRecords() {
  try {
    await client.connect();
    const collection = client.db().collection('mycollection');
    const documents = await collection.find({ age: { $gt: 25 } }).toArray();
    console.log('Retrieved documents:', documents);
  } catch (err) {
    console.error('Error reading records:', err);
  }
}

readRecords();

2.3. Updating Records
To modify existing data in the database, we use methods like updateOne in MongoDB.

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

const uri = 'mongodb://localhost:27017/mydatabase';
const client = new MongoClient(uri);

async function updateRecord(filter, update) {
  try {
    await client.connect();
    const collection = client.db().collection('mycollection');
    const result = await collection.updateOne(filter, update);
    console.log('Modified documents count:', result.modifiedCount);
  } catch (err) {
    console.error('Error updating record:', err);
  }
}

const filter = { name: 'John Doe' };
const update = { $set: { age: 35 } };
updateRecord(filter, update);

2.4. Deleting Records
To remove data from the database, we use methods like deleteOne in MongoDB.

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

const uri = 'mongodb://localhost:27017/mydatabase';
const client = new MongoClient(uri);

async function deleteRecord(filter) {
  try {
    await client.connect();
    const collection = client.db().collection('mycollection');
    const result = await collection.deleteOne(filter);
    console.log('Deleted documents count:', result.deletedCount);
  } catch (err) {
    console.error('Error deleting record:', err);
  }
}

const filter = { name: 'John Doe' };
deleteRecord(filter);

This documentation provides a brief overview of Node.js database access, including setting up connections, performing CRUD operations, and examples using MongoDB as an illustration. Remember that the specific implementation may vary based on the chosen database type and driver.