Nodejs database server setup

This article will introduce how to use Node.js to build a database server. Node.js is a server-side JavaScript development tool based on the Chrome JavaScript engine, which can easily implement asynchronous event-driven programming. When using Node.js for server development, we can use different frameworks and libraries to develop, the most popular of which is Express.js, but other frameworks can also achieve the same functionality. In order to make our server more scalable and reliable, we need to choose a database that suits us to store data. This article demonstrates how to use a MySQL database to store data.

1. Install Node.js and MySQL

Before we begin, we need to install Node.js and MySQL in the system. Node.js can be downloaded from the official website (https://nodejs.org), and MySQL can also be downloaded from the official website (https://www.mysql.com/).

2. Create database and data table

First, we need to create a database and a data table in MySQL to store our data. Use the following command to create a database named test:

CREATE DATABASE test;

Next, create a data table named users:

USE test;

CREATE TABLE users (
  id INT NOT NULL AUTO_INCREMENT,
  name VARCHAR(50) NOT NULL,
  email VARCHAR(100) NOT NULL,
  PRIMARY KEY (id),
  UNIQUE KEY email (email)
);

This table contains three columns: id, name, and email. The id column is an auto-increment column that ensures each entry has a unique ID. The name and email columns are required fields, so we define NOT NULL constraints in the table definition. The email column also has a unique key index to ensure that each email address appears only once.

3. Install the MySQL module

Next, we need to install the MySQL module in Node.js. We can use the npm command to install the mysql module:

npm install mysql

4. Connect to MySQL

Connecting to MySQL in the application requires the use of the mysql module. We need to use the connection information to instantiate the connection object:

const mysql = require('mysql');

const connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'user',
  password : 'password',
  database : 'test'
});

In this example, we define the database connection information. If your MySQL server is local, the hostname should be localhost. Note that passwords are used in this example, which is an insecure practice. In actual use, more secure measures need to be used, such as reading passwords from environment variables.

5. Writing API

Now, we can write an API to create new users, get user information, and delete users. We need to implement routing functionality through Express.js. In this example, we used Express.js.

const express = require('express');
const bodyParser = require('body-parser');

const app = express();
app.use(bodyParser.json());

// 创建新用户
app.post('/users', (req, res) => {
  const user = req.body;
  connection.query('INSERT INTO users SET ?', user, (err, results) => {
    if (err) {
      res.status(500).send(err);
    } else {
      res.status(200).send(results);
    }
  });
});

// 获取用户信息
app.get('/users/:id', (req, res) => {
  const id = req.params.id;
  connection.query('SELECT * FROM users WHERE id = ?', id, (err, results) => {
    if (err) {
      res.status(500).send(err);
    } else {
      res.status(200).send(results[0]);
    }
  });
});

// 删除用户
app.delete('/users/:id', (req, res) => {
  const id = req.params.id;
  connection.query('DELETE FROM users WHERE id = ?', id, (err, results) => {
    if (err) {
      res.status(500).send(err);
    } else {
      res.status(200).send(results);
    }
  });
});

// 启动服务器
app.listen(3000, () => {
  console.log('Server started on port 3000');
});

In the above code, we use the body-parser middleware to parse the incoming JSON data. It also supports parsing .urlencoded data. We define the router as POST, GET, and DELETE operations that will create new users, get user information, and delete users. In each request, we use the connection.query() function to execute the SQL query and return the results to the client. If the query fails, a 500 error is returned.

6. Testing the API

Now, we can test our API using the curl command. Here are some sample commands:

Create new user:

curl -X POST -H 'Content-Type: application/json' -d '{"name": "Alice", "email": "alice@example.com"}' http://localhost:3000/users

Get user information:

curl http://localhost:3000/users/1

Delete user:

curl -X DELETE http://localhost:3000/users/1

Now, we have successfully Created a simple database server using Node.js and MySQL. It can be extended to support more API operations, or use other database systems such as MongoDB or PostgreSQL.

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