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How to use Planetscale with Deno

Planetscale is a MySQL-compatible serverless database that is designed with a developer workflow where developers can create, branch, and deploy databases from the command line.

View source here.

We’ll use the Planetscale serverless driver, @planetscale/database, to work with Deno. First we want to create main.ts and import the connect method from this package:

import { connect } from "npm:@planetscale/database@^1.4";

Configuring our connection

The connection requires three credentials: host, username, and password. These are database-specific, so we first need to create a database in Planetscale. You can do that by following the initial instructions here. Don’t worry about adding the schema—we can do that through @planetscale/database.

Once you have created the database, head to Overview, click “Connect”, and choose “Connect with @planetscale/database” to get the host and username. Then click through to Passwords to create a new password for your database. Once you have all three you can plug them in directly, or better, store them as environment variables:

export HOST=<host>
export USERNAME=<username>
export PASSWORD=<password>

Then call them using Deno.env:

const config = {
  host: Deno.env.get("HOST"),
  username: Deno.env.get("USERNAME"),
  password: Deno.env.get("PASSWORD"),
};

const conn = connect(config);

This will also work on Deno Deploy if you set the environment variables in the dashboard. Run with:

deno run --allow-net --allow-env main.ts

The conn object is now an open connection to our Planetscale database.

Creating and populating our database table

Now that you have the connection running, you can conn.execute() with SQL commands to create tables and insert the initial data:

await conn.execute(
  "CREATE TABLE dinosaurs (id int NOT NULL AUTO_INCREMENT PRIMARY KEY, name varchar(255) NOT NULL, description varchar(255) NOT NULL);",
);
await conn.execute(
  "INSERT INTO `dinosaurs` (id, name, description) VALUES (1, 'Aardonyx', 'An early stage in the evolution of sauropods.'), (2, 'Abelisaurus', 'Abels lizard has been reconstructed from a single skull.'), (3, 'Deno', 'The fastest dinosaur that ever lived.')",
);

Querying Planetscale

We can use same conn.execute() to also write our queries. Let’s get a list of all our dinosaurs:

const results = await conn.execute("SELECT * FROM `dinosaurs`");
console.log(results.rows);

The result:

[
  {
    id: 1,
    name: "Aardonyx",
    description: "An early stage in the evolution of sauropods.",
  },
  {
    id: 2,
    name: "Abelisaurus",
    description: "Abels lizard has been reconstructed from a single skull.",
  },
  { id: 3, name: "Deno", description: "The fastest dinosaur that ever lived." },
];

We can also get just a single row from the database by specifying a dinosaur name:

const result = await conn.execute(
  "SELECT * FROM `dinosaurs` WHERE `name` = 'Deno'",
);
console.log(result.rows);

Which gives us a single row result:

[{ id: 3, name: "Deno", description: "The fastest dinosaur that ever lived." }];

You can find out more about working with Planetscale in their docs.

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