MySQL Installation & Setup

Installation

To install the MySQL client library, open a new Terminal and run:

yarn add @databases/mysql

Creating a database

If you don't already have a database to connect to, you can create one using pg-test:

yarn add @databases/mysql-test
yarn mysql-test start

This will print a connection string as the last line of it's output, it will look something like:

mysql://test-user:password@localhost:3306/test-db

N.B. This database does not have any persistence, it should only be used for testing things out/getting started. Please do not store anything even vaguely important in it.

When you're done testing out your app, you can shut the database down using:

yarn mysql-test stop

Running your first query

Database queries are always asynchronous, and return Promises, so you will need to await them to get the actual resulting vaules.

import createConnectionPool, {sql} from '@databases/mysql';

async function run() {
  // N.B. you will need to replace this connection
  // string with the correct string for your database.
  const db = createConnectionPool(
    'mysql://test-user:password@localhost:3306/test-db',
  );

  const results = await db.query(sql`
    SELECT 1 + 1 as result;
  `);

  console.log(results);
  // => [{result: 2}]

  await db.dispose();
}

run().catch((err) => {
  console.error(err);
  process.exit(1);
});

Connection Pools & Connection Strings

You should only create one connection pool for your application, otherwise your server will get slower and slower as more connection pools are created.

It is also bad practice to store your connection string in the actual code. You should use an environment variable instead.

You can read more about this in Managing Connections (which is the next section of this guide)