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Nodejs

Node.js connects to MySQL through the mysql npm package, which exposes a connection object created from a configuration object and a single query() method used for every statement.

Install

Install the package with npm:
npm install mysql

Installs the mysql package into the current Node.js project.

createConnection()

mysql.createConnection() builds a connection object from a configuration object specifying host, user, password, and database. It does not open the connection by itself.
var mysql = require('mysql');
var con = mysql.createConnection({ host: ..., user: ..., password: ..., database: ... });

Builds the connection object; the connection is not yet opened.

connect()

con.connect() opens the connection, invoking a callback with an error object (or null on success):
con.connect(function(err) { if (err) throw err; console.log("Connected!"); });

Opens the connection; err is non-null if the attempt failed.

query()

Every SQL statement – DDL (see Table Definitions), retrieval (see Data Retrieval), or manipulation (see Data Manipulation) – is run through con.query(), which takes the SQL string and a callback receiving err, result, and fields.

Node.js runs JavaScript as the client, outside the server – not to be confused with the JavaScript stored programs MySQL Enterprise Edition can run inside the server as of MySQL 9.0 (see Compound Statements).

ch07-mysql.js:
var mysql = require('mysql');

var con = mysql.createConnection({
    host: "localhost",
    user: "yourusername",
    password: "yourpassword",
    database: "mydb"
});

con.connect(function(err) {
    if (err) throw err;
    console.log("Connected!");

    con.query("SELECT * FROM customers", function (err, result, fields) {
        if (err) throw err;
        console.log(result);
    });
});