Getting started

Installation

Kysely can be installed using any of the following package managers:

npm

npm is the default package manager for Node.js, and to where Kysely is published.
Your project is using npm if it has a package-lock.json file in its root folder.

Run the following command in your terminal:

terminal

npm install kysely

pnpm

pnpm is a fast, disk space efficient package manager for Node.js.
Your project is using pnpm if it has a pnpm-lock.yaml file in its root folder.

Run the following command in your terminal:

terminal

pnpm install kysely

Yarn

Yarn is a fast, reliable and secure dependency manager for Node.js.
Your project is using Yarn if it has a yarn.lock file in its root folder.

Run the following command in your terminal:

terminal

yarn add kysely

Deno

Deno is a secure runtime for JavaScript and TypeScript.

Your root deno.json's "imports" field should include the following dependencies:

deno.json

{
  "imports": {
    "kysely": "npm:kysely@^0.25.0"
  }
}

Bun

Bun is a new JavaScript runtime built for speed, with a native bundler, transpiler, test runner, and npm-compatible package manager baked-in.

Run the following command in your terminal:

terminal

bun install kysely

Types

For Kysely's type-safety and autocompletion to work, it needs to know your database structure. This requires a TypeScript Database interface, that contains table names as keys and table schema interfaces as values.

Let's define our first database interface:

src/types.ts

import { ColumnType, Generated, Insertable, Selectable, Updatable } from 'kysely'

export interface Database {
  person: PersonTable
  pet: PetTable
}

export interface PersonTable {
  // Columns that are generated by the database should be marked
  // using the `Generated` type. This way they are automatically
  // made optional in inserts and updates.
  id: Generated<number>

  first_name: string
  gender: 'man' | 'woman' | 'other'

  // If the column is nullable in the database, make its type nullable.
  // Don't use optional properties. Optionality is always determined
  // automatically by Kysely.
  last_name: string | null

  // You can specify a different type for each operation (select, insert and
  // update) using the `ColumnType<SelectType, InsertType, UpdateType>`
  // wrapper. Here we define a column `created_at` that is selected as
  // a `Date`, can optionally be provided as a `string` in inserts and
  // can never be updated:
  created_at: ColumnType<Date, string | undefined, never>
}

// You should not use the table schema interfaces directly. Instead, you should
// use the `Selectable`, `Insertable` and `Updateable` wrappers. These wrappers
// make sure that the correct types are used in each operation.
export type Person = Selectable<PersonTable>
export type NewPerson = Insertable<PersonTable>
export type EditedPerson = Updateable<PersonTable>

export interface PetTable {
  id: Generated<number>
  name: string
  owner_id: number
  species: 'dog' | 'cat'
}

export type Pet = Selectable<PetTable>
export type NewPet = Insertable<PetTable>
export type EditedPet = Updateable<PetTable>

Codegen

For production apps, it is recommended to automatically generate your Database interface by introspecting your production database or Prisma schemas. Find out more at "Generating types".

Dialects

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Instantiation

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Querying

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Summary

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