Kysely Codegen

kysely-codegen generates Kysely type definitions from your database. That's it.

Table of contents

• Installation
• Generating type definitions
• Using the type definitions

Installation

npm install --save-dev kysely-codegen

# You will also need to install Kysely with your driver of choice:
npm install kysely pg
npm install kysely mysql2
npm install kysely better-sqlite3

Generating type definitions

The most convenient way to get started is to create an .env file with your database connection string:

# PostgreSQL
DATABASE_URL=postgres://username:password@yourdomain.com/database

# MySQL
DATABASE_URL=mysql://username:password@yourdomain.com/database

# SQLite
DATABASE_URL=C:/Program Files/sqlite3/db

Then run:

kysely-codegen

This command will generate a .d.ts file from your database, for example:

1import { Generated, ColumnType } from 'kysely';
2
3export type Timestamp = ColumnType<Date, Date | string, Date | string>;
4
5export interface Company {
6  id: Generated<number>;
7  name: string;
8}
9
10export interface User {
11  company_id: number | null;
12  created_at: Generated<Timestamp>;
13  email: string;
14  id: Generated<number>;
15  is_active: boolean;
16  name: string;
17  updated_at: Timestamp;
18}
19
20export interface DB {
21  company: Company;
22  user: User;
23}

For more options, run kysely-codegen --help.

Using the type definitions

Import DB into new Kysely<DB>, and you're done!

1import { Kysely, PostgresDialect } from 'kysely';
2import { DB } from 'kysely-codegen';
3import { Pool } from 'pg';
4
5const db = new Kysely<DB>({
6  dialect: new PostgresDialect({
7    pool: new Pool({
8      connectionString: process.env.DATABASE_URL,
9    }),
10  }),
11});
12
13const rows = await db.selectFrom('user').selectAll().execute();
14// [
15//   {
16//     company_id: number | null;
17//     created_at: Date;
18//     email: string;
19//     id: number;
20//     is_active: boolean;
21//     name: string;
22//     updated_at: Date;
23//   }
24// ]