Get Started with Drizzle and SQLite in existing project

Basic file structure

This is the basic file structure of the project. In the src/db directory, we have table definition in schema.ts. In drizzle folder there are sql migration file and snapshots.

📦 <project root>
 ├ 📂 drizzle
 ├ 📂 src
 │   ├ 📂 db
 │   │  └ 📜 schema.ts
 │   └ 📜 index.ts
 ├ 📜 .env
 ├ 📜 drizzle.config.ts
 ├ 📜 package.json
 └ 📜 tsconfig.json

Step 1 - Install required packages

npm i drizzle-orm dotenv
npm i -D drizzle-kit @types/bun

yarn add drizzle-orm dotenv
yarn add -D drizzle-kit @types/bun

pnpm add drizzle-orm dotenv
pnpm add -D drizzle-kit @types/bun

bun add drizzle-orm dotenv
bun add -D drizzle-kit @types/bun

Step 2 - Setup connection variables

Create a .env file in the root of your project and add your database connection variable:

DATABASE_URL=

Step 3 - Setup Drizzle config file

Drizzle config - a configuration file that is used by Drizzle Kit and contains all the information about your database connection, migration folder and schema files.

Create a drizzle.config.ts file in the root of your project and add the following content:

import 'dotenv/config';
import { defineConfig } from 'drizzle-kit';

export default defineConfig({
  out: './drizzle',
  schema: './src/db/schema.ts',
  dialect: 'postgresql',
  dbCredentials: {
    url: process.env.DATABASE_URL!,
  },
});

Step 4 - Introspect your database

Drizzle Kit provides a CLI command to introspect your database and generate a schema file with migrations. The schema file contains all the information about your database tables, columns, relations, and indices.

For example, you have such table in your database:

CREATE TABLE IF NOT EXISTS "users" (
	"id" integer PRIMARY KEY GENERATED ALWAYS AS IDENTITY (sequence name "users_id_seq" INCREMENT BY 1 MINVALUE 1 MAXVALUE 2147483647 START WITH 1 CACHE 1),
	"name" varchar(255) NOT NULL,
	"age" integer NOT NULL,
	"email" varchar(255) NOT NULL,
	CONSTRAINT "users_email_unique" UNIQUE("email")
);

Pull your database schema:

npx drizzle-kit pull

The result of introspection will be a schema.ts file, meta folder with snapshots of your database schema, sql file with the migration and relations.ts file for relational queries.

Here is an example of the generated schema.ts file:

// table schema generated by introspection
import { pgTable, unique, integer, varchar } from "drizzle-orm/pg-core"
import { sql } from "drizzle-orm"

export const users = pgTable("users", {
	id: integer().primaryKey().generatedAlwaysAsIdentity({ name: "users_id_seq", startWith: 1, increment: 1, minValue: 1, maxValue: 2147483647, cache: 1 }),
	name: varchar({ length: 255 }).notNull(),
	age: integer().notNull(),
	email: varchar({ length: 255 }).notNull(),
}, (table) => [
	unique("users_email_unique").on(table.email)
]);

Learn more about introspection in the documentation.

Step 5 - Transfer code to your actual schema file

We recommend transferring the generated code from drizzle/schema.ts and drizzle/relations.ts to the actual schema file. In this guide we transferred code to src/db/schema.ts. Generated files for schema and relations can be deleted. This way you can manage your schema in a more structured way.

 ├ 📂 drizzle
 │ ├ 📂 meta
 │ ├ 📜 migration.sql
 │ ├ 📜 relations.ts ────────┐
 │ └ 📜 schema.ts ───────────┤
 ├ 📂 src                    │ 
 │ ├ 📂 db                   │
 │ │ ├ 📜 relations.ts <─────┤
 │ │ └ 📜 schema.ts <────────┘
 │ └ 📜 index.ts         
 └ …

Step 6 - Connect Drizzle ORM to the database

Create a index.ts file in the src directory and initialize the connection:

import 'dotenv/config';
import { drizzle } from 'drizzle-orm/bun-sql';

const db = drizzle(process.env.DATABASE_URL!);

import 'dotenv/config';
import { drizzle } from 'drizzle-orm/bun-sql';

// You can specify any property from the bun sql connection options
const db = drizzle({ connection: { url: process.env.DATABASE_URL! }});

If you need to provide your existing driver:

import 'dotenv/config';
import { drizzle } from 'drizzle-orm/bun-sql';
import { SQL } from 'bun';

const client = new SQL(process.env.DATABASE_URL!);
const db = drizzle({ client });

Step 7 - Query the database

Let’s update the src/index.ts file with queries to create, read, update, and delete users

import 'dotenv/config';
import { drizzle } from 'drizzle-orm/bun-sql';
import { eq } from 'drizzle-orm';
import { usersTable } from './db/schema';
  
const db = drizzle(process.env.DATABASE_URL!);

async function main() {
  const user: typeof usersTable.$inferInsert = {
    name: 'John',
    age: 30,
    email: '[email protected]',
  };

  await db.insert(usersTable).values(user);
  console.log('New user created!')

  const users = await db.select().from(usersTable);
  console.log('Getting all users from the database: ', users)
  /*
  const users: {
    id: number;
    name: string;
    age: number;
    email: string;
  }[]
  */

  await db
    .update(usersTable)
    .set({
      age: 31,
    })
    .where(eq(usersTable.email, user.email));
  console.log('User info updated!')

  await db.delete(usersTable).where(eq(usersTable.email, user.email));
  console.log('User deleted!')
}

main();

Step 8 - Run index.ts file

To run a script with bun, use the following command:

bun src/index.ts

Step 9 - Update your table schema (optional)

If you want to update your table schema, you can do it in the schema.ts file. For example, let’s add a new column phone to the users_table:

import { pgTable, unique, integer, varchar } from "drizzle-orm/pg-core"
import { sql } from "drizzle-orm"

export const users = pgTable("users", {
	id: integer().primaryKey().generatedAlwaysAsIdentity({ name: "users_id_seq", startWith: 1, increment: 1, minValue: 1, maxValue: 2147483647, cache: 1 }),
	name: varchar({ length: 255 }).notNull(),
	age: integer().notNull(),
	email: varchar({ length: 255 }).notNull(),
  phone: varchar(),
}, (table) => [
	unique("users_email_unique").on(table.email)
]);

Step 9 - Applying changes to the database (optional)

You can directly apply changes to your database using the drizzle-kit push command. This is a convenient method for quickly testing new schema designs or modifications in a local development environment, allowing for rapid iterations without the need to manage migration files:

npx drizzle-kit push

Read more about the push command in documentation.

npx drizzle-kit generate

npx drizzle-kit migrate

Step 10 - Query the database with a new field (optional)

import 'dotenv/config';
import { drizzle } from 'drizzle-orm/bun-sql';
import { eq } from 'drizzle-orm';
import { usersTable } from './db/schema';

const db = drizzle(process.env.DATABASE_URL!);

async function main() {
  const user: typeof usersTable.$inferInsert = {
    name: 'John',
    age: 30,
    email: '[email protected]',
    phone: '123-456-7890',
  };

  await db.insert(usersTable).values(user);
  console.log('New user created!')

  const users = await db.select().from(usersTable);
  console.log('Getting all users from the database: ', users)
  /*
  const users: {
    id: number;
    name: string;
    age: number;
    email: string;
    phone: string | null;
  }[]
  */

  await db
    .update(usersTable)
    .set({
      age: 31,
    })
    .where(eq(usersTable.email, user.email));
  console.log('User info updated!')

  await db.delete(usersTable).where(eq(usersTable.email, user.email));
  console.log('User deleted!')
}

main();