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Connecting to databases

It is common for applications to store and retrieve data from databases. Deno supports connecting to many database management systems.

The Deno community has published a number of third-party modules that make it easy to connect to popular databases like MySQL, Postgres, and MongoDB.

They are hosted at Deno's third-party module site deno.land/x.

MySQL Jump to heading

deno_mysql is a MySQL and MariaDB database driver for Deno.

Connect to MySQL with deno_mysql Jump to heading

First import the mysql module and create a new client instance. Then connect to the database passing an object with the connection details:

main.js
import { Client } from "https://deno.land/x/mysql/mod.ts";

const client = await new Client().connect({
  hostname: "127.0.0.1",
  username: "root",
  db: "dbname",
  password: "password",
});

Once connected, you can execute queries, insert data and retrive information.

Postgres Jump to heading

deno-postgres is a lightweight PostgreSQL driver for Deno focused on developer experience.

Connect to Postgres with deno-postgres Jump to heading

First, import the Client class from the deno-postgres module and create a new client instance. Then connect to the database passing an object with the connection details:

import { Client } from "https://deno.land/x/postgres/mod.ts";

const client = new Client({
  user: "user",
  database: "dbname",
  hostname: "127.0.0.1",
  port: 5432,
  password: "password",
});
await client.connect();

Connect to Postgres with postgresjs Jump to heading

postgresjs is a full-featured Postgres client for Node.js and Deno.

Import the postgres module and create a new client instance. Then connect to the database passing a connection string as an argument:

import postgres from "https://deno.land/x/postgresjs/mod.js";

const sql = postgres("postgres://username:password@host:port/database");

MongoDB Jump to heading

We suggest using npm specifiers to work with the official MongoDB driver on npm. You can learn more about how to work with the driver in the official docs. The only difference using this module in the context of Deno will be how you import the module using an npm: specifier.

Import the MongoDB driver, set up connection configuration then connect to a MongoDB instance. You can then perform operations like inserting documents into a collection before closing the connection:

main.js
import { MongoClient } from "npm:mongodb@6";

const url = "mongodb://localhost:27017";
const client = new MongoClient(url);
const dbName = "myProject";

await client.connect();
console.log("Connected successfully to server");

// Get a reference to a collection
const db = client.db(dbName);
const collection = db.collection("documents");

// Execute an insert operation
const insertResult = await collection.insertMany([{ a: 1 }, { a: 2 }]);
console.log("Inserted documents =>", insertResult);

client.close();

SQLite Jump to heading

There are multiple solutions to connect to SQLite in Deno:

Connect to SQLite using the node:sqlite module Jump to heading

node:sqlite module has been added in Deno v2.2.

import { DatabaseSync } from "node:sqlite";
const database = new DatabaseSync("test.db");

const result = database.prepare("select sqlite_version()").get();
console.log(result);

db.close();

Connect to SQLite with the FFI Module Jump to heading

@db/sqlite provides JavaScript bindings to the SQLite3 C API, using Deno FFI.

import { Database } from "jsr:@db/sqlite@0.12";

const db = new Database("test.db");

const [version] = db.prepare("select sqlite_version()").value<[string]>()!;
console.log(version);

db.close();

Connect to SQLite with the Wasm-Optimized Module Jump to heading

sqlite is a SQLite module for JavaScript and TypeScript. The wrapper made specifically for Deno and uses a version of SQLite3 compiled to WebAssembly (Wasm).

import { DB } from "https://deno.land/x/sqlite/mod.ts";

const db = new DB("test.db");

db.close();

Firebase Jump to heading

To connect to Firebase with Deno, import the firestore npm module with the ESM CDN. To learn more about using npm modules in Deno with a CDN, see Using npm packages with CDNs.

Connect to Firebase with the firestore npm module Jump to heading

import { initializeApp } from "https://www.gstatic.com/firebasejs/9.8.1/firebase-app.js";

import {
  addDoc,
  collection,
  connectFirestoreEmulator,
  deleteDoc,
  doc,
  Firestore,
  getDoc,
  getDocs,
  getFirestore,
  query,
  QuerySnapshot,
  setDoc,
  where,
} from "https://www.gstatic.com/firebasejs/9.8.1/firebase-firestore.js";

import { getAuth } from "https://www.gstatic.com/firebasejs/9.8.1/firebase-auth.js";

const app = initializeApp({
  apiKey: Deno.env.get("FIREBASE_API_KEY"),
  authDomain: Deno.env.get("FIREBASE_AUTH_DOMAIN"),
  projectId: Deno.env.get("FIREBASE_PROJECT_ID"),
  storageBucket: Deno.env.get("FIREBASE_STORAGE_BUCKET"),
  messagingSenderId: Deno.env.get("FIREBASE_MESSING_SENDER_ID"),
  appId: Deno.env.get("FIREBASE_APP_ID"),
  measurementId: Deno.env.get("FIREBASE_MEASUREMENT_ID"),
});
const db = getFirestore(app);
const auth = getAuth(app);

Supabase Jump to heading

To connect to Supabase with Deno, import the supabase-js npm module with the esm.sh CDN. To learn more about using npm modules in Deno with a CDN, see Using npm packages with CDNs.

Connect to Supabase with the supabase-js npm module Jump to heading

import { createClient } from "https://esm.sh/@supabase/supabase-js";

const options = {
  schema: "public",
  headers: { "x-my-custom-header": "my-app-name" },
  autoRefreshToken: true,
  persistSession: true,
  detectSessionInUrl: true,
};

const supabase = createClient(
  "https://xyzcompany.supabase.co",
  "public-anon-key",
  options,
);

ORMs Jump to heading

Object-Relational Mappings (ORM) define your data models as classes that you can persist to a database. You can read and write data in your database through instances of these classes.

Deno supports multiple ORMs, including Prisma and DenoDB.

DenoDB Jump to heading

DenoDB is a Deno-specific ORM.

Connect to DenoDB Jump to heading

import {
  Database,
  DataTypes,
  Model,
  PostgresConnector,
} from "https://deno.land/x/denodb/mod.ts";

const connection = new PostgresConnector({
  host: "...",
  username: "user",
  password: "password",
  database: "airlines",
});

const db = new Database(connection);

GraphQL Jump to heading

GraphQL is an API query language often used to compose disparate data sources into client-centric APIs. To set up a GraphQL API, you should first set up a GraphQL server. This server exposes your data as a GraphQL API that your client applications can query for data.

Server Jump to heading

You can use gql, an universal GraphQL HTTP middleware for Deno, to run a GraphQL API server in Deno.

Run a GraphQL API server with gql Jump to heading

import { GraphQLHTTP } from "https://deno.land/x/gql/mod.ts";
import { makeExecutableSchema } from "https://deno.land/x/graphql_tools@0.0.2/mod.ts";
import { gql } from "https://deno.land/x/graphql_tag@0.0.1/mod.ts";

const typeDefs = gql`
  type Query {
    hello: String
  }
`;

const resolvers = {
  Query: {
    hello: () => `Hello World!`,
  },
};

const schema = makeExecutableSchema({ resolvers, typeDefs });

Deno.serve({ port: 3000 }, async () => {
  const { pathname } = new URL(req.url);

  return pathname === "/graphql"
    ? await GraphQLHTTP<Request>({
      schema,
      graphiql: true,
    })(req)
    : new Response("Not Found", { status: 404 });
});

Client Jump to heading

To make GraphQL client calls in Deno, import the graphql npm module with the esm CDN. To learn more about using npm modules in Deno via CDN read here.

Make GraphQL client calls with the graphql npm module Jump to heading

import { buildSchema, graphql } from "https://esm.sh/graphql";

const schema = buildSchema(`
type Query {
  hello: String
}
`);

const rootValue = {
  hello: () => {
    return "Hello world!";
  },
};

const response = await graphql({
  schema,
  source: "{ hello }",
  rootValue,
});

console.log(response);

🦕 Now you can connect your Deno project to a database you'll be able to work with persistent data, perform CRUD operations and start building more complex applications.

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