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Getting started


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

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:

npm install kysely


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:

import { ColumnType, Generated, Insertable, Selectable, Updateable } 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 PersonUpdate = 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 PetUpdate = Updateable<PetTable>

For production apps, it is recommended to automatically generate your Database interface by introspecting your production database or Prisma schemas. Generated types might differ in naming convention, internal order, etc. Find out more at "Generating types".