mysql2/promise require database connection file

Question

I have only been working with PHP before going to Node.JS. What I was able to do in PHP when working with MYSQL was that I could include the database.php file in the files I wanted to execure queries in.

It doesn't seem to be the same in Node.Js. This is my database.js file

const mysql  = require("mysql2/promise");

const db = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'XXXX',
    database: 'nodelogin'
});

module.exports = db;

Then I require this in my file login.js

const db  = require("../../database");

However, when I then try to run db.query(sql, [variable]) I get db.query is not a function.

Why is this? It shouldn't be that more complicated or should it?

you need to await the await mysql.createConnection.. db will be a Promise at that point and won't contain the methods.. rtm: npmjs.com/package/mysql2#using-promise-wrapper — Lawrence Cherone
– Lawrence Cherone, Commented Mar 11, 2021 at 13:28

Terry Lennox · Accepted Answer · 2021-03-11 13:46:47Z

2

If you use a connection pool instead, you can include the pool once, then call query on it, like so:

db-config.js

const mysql = require("mysql2/promise");

console.log("Creating connection pool...")
const pool = mysql.createPool({
    host: 'localhost',
    user: 'user',
    database: 'test_db',
    password: 'password'
})

module.exports = pool;

test.js

// Require to whereever db-config is 
const pool = require('./db-config.js');

async function testQuery() {
    const results = await pool.query("select * from users");
    console.table(results[0]);
}

testQuery();

edited Mar 11, 2021 at 13:46

answered Mar 11, 2021 at 13:30

Terry Lennox

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3 Comments

Lawrence Cherone Over a year ago

doing it this way, require is cached, but on multiple places like inside express handlers will quickly hammer connections, anti-pattern

Emrik Ahlström Over a year ago

but this means I have to include "database.js" in every query I make? Isn't there a way to just include it once in each file?

Terry Lennox Over a year ago

Good point @LawrenceCherone, I've updated the answer.

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