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Getting started

Installation

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:

terminal
npm 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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