Javascript with database connection

Node.js and MySQL Complete Tutorial

Node.js and MySQL are some of the necessary binding needed for any web application. MySQL is one of the most popular open-source databases in the world and is efficient as well. Almost every popular programming language like Java and PHP provides drivers to access and perform operations with MySQL.

In this Node js and MySQL tutorial, we are going to learn how to connect the Node js server with a MySQL database. We will also learn how to pool connections to improve performance, query the tables, and call stored procedures.

To be able to follow up with the code examples in this Node.js and MySQL tutorial, you should have MySQL installed on your computer, click here to download MySQL.

Quick Start: How to Use MySQL in Node

Assuming you have Node and MySQL installed on your computer. Let’s quickly use MySQL in Node in three easy steps:

Step 1: Create a new Node.js project

Create a new directory and initialize a Node project using the NPM.

$ mkdir mysqlexperiment && cd mysqlexperiment $ npm init --y

Step 2: Install mysql node module

Install the mysql node module using the NPM.

Step 3: Connect with MySQL

Create an app.js file and copy/paste the code shown below. Change the MySQL credentials accordingly with your system.

const mysql = require('mysql'); const connection = mysql.createConnection(< host: 'localhost', user: 'user', password: 'password', database: 'databasename' >); connection.connect((err) => < if (err) throw err; console.log('Connected to MySQL Server!'); >);

Run the code using the following command.

Observe the ‘Connected to MySQL Server!’ message in the terminal.

If you have the latest MySQL server installed, you might end up getting an error saying the following.

To tackle this issue, create a new user in your MySQL server with ‘mysql_native_password’ authentication mechanisum.

Here is how you can do it quickly. First, log in to the MySQL server using root access.

Then run these commands one by one.

CREATE USER 'newuser'@'localhost' IDENTIFIED WITH 'mysql_native_password' BY 'newpassword'; GRANT ALL PRIVILEGES ON * . * TO 'newuser'@'localhost'; FLUSH PRIVILEGES;

In the code, pass the new credentials to connect to the MySQL server. Let’s proceed further.

Pooling MySQL Connections

The code shown earlier is not meant for production use. It’s merely to get you started with Node and MySQL. In a production scenario, we must use connection pooling to improve the performance of MySQL and not overload the MySQL server with too many connections.

Let’s explain it with a simple example.

Consider the code shown below.

const express = require("express"); const app = express(); const mysql = require('mysql'); const connection = mysql.createConnection(< host: 'localhost', user: 'username', password: 'password', database: 'databasename' >); connection.connect((err) => < if (err) throw err; console.log('Connected to MySQL Server!'); >); app.get("/", (req, res) => < connection.query('SELECT * from users LIMIT 1', (err, rows) =>< if (err) throw err; console.log('The data from users table are: \n', rows); connection.end(); >); >); app.listen(3000, () => < console.log('Server is running at port 3000'); >);

We are integrating express module to create a web server. Install the module using the following command.

We are creating a MySQL connection on every request coming from the user. Soon after getting multiple concurrent requests, the MySQL server will get overloaded and throw an error.

To simulate the concurrent connection scenario, we are going to use a tool called siege.

Use this command to install it in Ubuntu system.

sudo apt-get install siege

Let’s simulate the concurrent requests.

siege -c10 -t1M http://localhost:3000

Assuming you are running the Node server on Port 3000.

As you can see from the output above, our server crashed while handling concurrent requests. To tackle this scenario, we use the Pooling mechanism.

Connection Pooling is a mechanism to maintain a cache of database connection so that the connection can be reused after releasing it.

Let’s rewrite our code to support connection pooling.

const express = require("express"); const app = express(); const mysql = require('mysql'); const pool = mysql.createPool(< host: 'localhost', user: 'username', password: 'password', database: 'databasename' >); app.get("/", (req, res) => < pool.getConnection((err, connection) => < if (err) throw err; console.log('connected as id ' + connection.threadId); connection.query('SELECT * from users LIMIT 1', (err, rows) =>< connection.release(); // return the connection to pool if (err) throw err; console.log('The data from users table are: \n', rows); >); >); >); app.listen(3000, () => < console.log('Server is running at port 3000'); >);

Run the app using the following command.

Let’s fire up 10 concurrent users for 1 minute using siege by using this command.

siege -c10 -t1M http://localhost:3000

Our server is effectively handling multiple requests with ease. I have used this approach in multiple production software solutions with heavy payload and it works like charm.

Let’s learn how to execute various MySQL queries using Node.

Executing Queries

Let’s learn how to execute queries using Node.js.

Inserting data into Table

Here is the code to add new rows to the table.

const mysql = require('mysql'); const pool = mysql.createPool(< connectionLimit: 100, //important host: 'localhost', user: 'root', password: '', database: 'todolist', debug: false >); // add rows in the table function addRow(data) < let insertQuery = 'INSERT INTO ?? (. ) VALUES (. )'; let query = mysql.format(insertQuery, ["todo", "user", "notes", data.user, data.value]); pool.query(query, (err, response) => < if (err) < console.error(err); return; >// rows added console.log(response.insertId); >); > // timeout just to avoid firing query before connection happens setTimeout(() => < // call the function addRow(< "user": "Shahid", "value": "Just adding a note" >); >, 5000);

The mysql.format function will perform the query escape.

Selecting data in Table

Here is the code to query rows in the table.

const mysql = require('mysql'); const pool = mysql.createPool(< connectionLimit: 100, //important host: 'localhost', user: 'root', password: '', database: 'todolist', debug: false >); // query rows in the table function queryRow(userName) < let selectQuery = 'SELECT * FROM ?? WHERE ?? = ?'; let query = mysql.format(selectQuery, ["todo", "user", userName]); // query = SELECT * FROM `todo` where `user` = 'shahid' pool.query(query, (err, data) => < if (err) < console.error(err); return; >// rows fetch console.log(data); >); > // timeout just to avoid firing query before connection happens setTimeout(() => < // call the function // select rows queryRow('shahid'); >, 5000);

If you would like to add multiple rows in a single query, you can pass an array in the values. Like this.

let insertQuery = 'INSERT INTO ?? (. ) VALUES (. ); let values = [["shahid","hello"],["Rohit","Hi"]]; // each array is one row let query = mysql.format(insertQuery,["todo","user","notes",values]);

Updating data in Table

Here is the code to update the data in the table.

const mysql = require('mysql'); const pool = mysql.createPool(< connectionLimit: 100, //important host: 'localhost', user: 'root', password: '', database: 'todolist', debug: false >); // update rows function updateRow(data) < let updateQuery = "UPDATE ?? SET ?? = ? WHERE ?? = ?"; let query = mysql.format(updateQuery, ["todo", "notes", data.value, "user", data.user]); // query = UPDATE `todo` SET `notes`='Hello' WHERE `name`='shahid' pool.query(query, (err, response) => < if (err) < console.error(err); return; >// rows updated console.log(response.affectedRows); >); > // timeout just to avoid firing query before connection happens setTimeout(() => < // call the function // update row updateRow(< "user": "Shahid", "value": "Just updating a note" >); >, 5000);

Deleting Rows in the table

Here is the code to delete a row from the table.

const mysql = require('mysql'); const pool = mysql.createPool(< connectionLimit: 100, //important host: 'localhost', user: 'root', password: '', database: 'todolist', debug: false >); function deleteRow(userName) < let deleteQuery = "DELETE from ?? where ?? = ?"; let query = mysql.format(deleteQuery, ["todo", "user", userName]); // query = DELETE from `todo` where `user`='shahid'; pool.query(query, (err, response) => < if (err) < console.error(err); return; >// rows deleted console.log(response.affectedRows); >); > // timeout just to avoid firing query before connection happens setTimeout(() => < // call the function // delete row deleteRow('shahid'); >, 5000);

Calling MySQL Stored Procedure Using Node

When a SQL query run in order to retrieve some data from the MySQL database, MySQL executes that query and returns the requested data, and if our system requires querying the same data regularly we have to write over and over again multiple times, so to solve that problem stored procedure comes into existence. A store procedure can store SQL statements in the MySQL server which can be directly run by calling that stored procedure.

You can also call a stored procedure directly using Node.js. If you don’t have stored procedures created in MySQL, you can refer to the code below to do the same.

CREATE PROCEDURE `getAllTodo`() BEGIN SELECT * FROM todo; END$$

Here is the code to call this stored procedure from the Node.js code:

const mysql = require('mysql'); const pool = mysql.createPool(< connectionLimit: 100, //important host: 'localhost', user: 'root', password: '', database: 'todolist', debug: false >); function callSP(spName) < let spQuery = 'CALL ??'; let query = mysql.format(spQuery, [spName]); // CALL `getAllTodo` pool.query(query, (err, result) => < if (err) < console.error(err); return; >// rows from SP console.log(result); >); > // timeout just to avoid firing query before connection happens setTimeout(() => < // call the function // call sp callSP('getAllTodo') >, 5000);

Conclusion

In this tutorial we have learned how to use MySQL in Node.js which we have done using the npm mysql module, we have also learned connection pooling and execute SQL queries directly from Node.js to insert data into tables, query data in tables, update and delete data in the table and finally, we have learned to call MySQL stored procedure using Node.js. Node.js supports all types of databases but it works very well with MySQL, so don’t forget to try it after reading this tutorial.

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Node.js MySQL

To be able to experiment with the code examples, you should have MySQL installed on your computer.

You can download a free MySQL database at https://www.mysql.com/downloads/.

Install MySQL Driver

Once you have MySQL up and running on your computer, you can access it by using Node.js.

To access a MySQL database with Node.js, you need a MySQL driver. This tutorial will use the «mysql» module, downloaded from NPM.

To download and install the «mysql» module, open the Command Terminal and execute the following:

Now you have downloaded and installed a mysql database driver.

Node.js can use this module to manipulate the MySQL database:

Create Connection

Start by creating a connection to the database.

Use the username and password from your MySQL database.

var con = mysql.createConnection( host: «localhost»,
user: «yourusername«,
password: «yourpassword»
>);

con.connect(function(err) if (err) throw err;
console.log(«Connected!»);
>);

Save the code above in a file called «demo_db_connection.js» and run the file:

Which will give you this result:

Now you can start querying the database using SQL statements.

Query a Database

Use SQL statements to read from (or write to) a MySQL database. This is also called «to query» the database.

The connection object created in the example above, has a method for querying the database:

con.connect(function(err) <
if (err) throw err;
console.log(«Connected!»);
con.query(sql, function (err, result) <
if (err) throw err;
console.log(«Result: » + result);
>);
>);

The query method takes an sql statements as a parameter and returns the result.

Learn how to read, write, delete, and update a database in the next chapters.

Read more about SQL statements in our SQL Tutorial.

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