TypeScript ORM for Node.js based on Data Mapper, [Unit of Work](https://mikro-orm.io/docs/unit-of-work/) and [Identity Map](https://mikro-orm.io/docs/identity-map/) patterns. Supports MongoDB, MySQL, MariaDB, PostgreSQL, SQLite (including libSQL), MSSQL and Oracle databases. > Heavily inspired by [Doctrine](https://www.doctrine-project.org/) and [Hibernate](https://hibernate.org/). [](https://npmx.dev/package/@mikro-orm/core) [](https://npmx.dev/package/@mikro-orm/core) [](https://discord.gg/w8bjxFHS7X) [](https://npmx.dev/package/@mikro-orm/core) [](https://coveralls.io/r/mikro-orm/mikro-orm?branch=master) [](https://github.com/mikro-orm/mikro-orm/actions?workflow=tests) ## Quick Start Install a driver package for your database: ```sh npm install @mikro-orm/postgresql # PostgreSQL npm install @mikro-orm/mysql # MySQL npm install @mikro-orm/mariadb # MariaDB npm install @mikro-orm/sqlite # SQLite npm install @mikro-orm/libsql # libSQL / Turso npm install @mikro-orm/mongodb # MongoDB npm install @mikro-orm/mssql # MS SQL Server npm install @mikro-orm/oracledb # Oracle ``` > If you use additional packages like `@mikro-orm/cli`, `@mikro-orm/migrations`, or `@mikro-orm/entity-generator`, install `@mikro-orm/core` explicitly as well. See the [quick start guide](https://mikro-orm.io/docs/quick-start) for details. ### Define Entities The recommended way to define entities is using [`defineEntity`](https://mikro-orm.io/docs/define-entity) with `setClass`: ```typescript import { defineEntity, p, MikroORM } from '@mikro-orm/postgresql'; const AuthorSchema = defineEntity({ name: 'Author', properties: { id: p.integer().primary(), name: p.string(), email: p.string(), born: p.datetime().nullable(), books: () => p.oneToMany(Book).mappedBy('author'), }, }); export class Author extends AuthorSchema.class {} AuthorSchema.setClass(Author); const BookSchema = defineEntity({ name: 'Book', properties: { id: p.integer().primary(), title: p.string(), author: () => p.manyToOne(Author).inversedBy('books'), }, }); export class Book extends BookSchema.class {} BookSchema.setClass(Book); ``` You can also define entities using [decorators](https://mikro-orm.io/docs/using-decorators) or [`EntitySchema`](https://mikro-orm.io/docs/define-entity#entityschema-low-level-api). See the [defining entities guide](https://mikro-orm.io/docs/defining-entities) for all options. ### Initialize and Use ```typescript import { MikroORM, RequestContext } from '@mikro-orm/postgresql'; const orm = await MikroORM.init({ entities: [Author, Book], dbName: 'my-db', }); // Create new entities const author = orm.em.create(Author, { name: 'Jon Snow', email: 'snow@wall.st', }); const book = orm.em.create(Book, { title: 'My Life on The Wall', author, }); // Flush persists all tracked changes in a single transaction await orm.em.flush(); ``` ### Querying ```typescript // Find with relations const authors = await orm.em.findAll(Author, { populate: ['books'], orderBy: { name: 'asc' }, }); // Type-safe QueryBuilder const qb = orm.em.createQueryBuilder(Author); const result = await qb .select('*') .where({ books: { title: { $like: '%Wall%' } } }) .getResult(); ``` ### Request Context In web applications, use `RequestContext` to isolate the identity map per request: ```typescript const app = express(); app.use((req, res, next) => { RequestContext.create(orm.em, next); }); ``` More info about `RequestContext` is described [here](https://mikro-orm.io/docs/identity-map/#request-context). ## Unit of Work > Unit of Work maintains a list of objects (_entities_) affected by a business transaction > and coordinates the writing out of changes. [(Martin Fowler)](https://www.martinfowler.com/eaaCatalog/unitOfWork.html) When you call `em.flush()`, all computed changes are queried inside a database transaction. This means you can control transaction boundaries simply by making changes to your entities and calling `flush()` when ready. ```typescript const author = await em.findOneOrFail(Author, 1, { populate: ['books'], }); author.name = 'Jon Snow II'; author.books.getItems().forEach(book => (book.title += ' (2nd ed.)')); author.books.add(orm.em.create(Book, { title: 'New Book', author })); // Flush computes change sets and executes them in a single transaction await em.flush(); ``` The above flush will execute: ```sql begin; update "author" set "name" = 'Jon Snow II' where "id" = 1; update "book" set "title" = case when ("id" = 1) then 'My Life on The Wall (2nd ed.)' when ("id" = 2) then 'Another Book (2nd ed.)' else "title" end where "id" in (1, 2); insert into "book" ("title", "author_id") values ('New Book', 1); commit; ``` ## Core Features - [Clean and Simple Entity Definition](https://mikro-orm.io/docs/defining-entities) — decorators, `EntitySchema`, or `defineEntity` - [Identity Map](https://mikro-orm.io/docs/identity-map) and [Unit of Work](https://mikro-orm.io/docs/unit-of-work) — automatic change tracking - [Entity References](https://mikro-orm.io/docs/entity-references) and [Collections](https://mikro-orm.io/docs/collections) - [QueryBuilder](https://mikro-orm.io/docs/query-builder) and [Kysely Integration](https://mikro-orm.io/docs/kysely) - [Transactions](https://mikro-orm.io/docs/transactions) and [Cascading](https://mikro-orm.io/docs/cascading) - [Populating Relations](https://mikro-orm.io/docs/populating-relations) and [Loading Strategies](https://mikro-orm.io/docs/loading-strategies) - [Filters](https://mikro-orm.io/docs/filters) and [Lifecycle Hooks](https://mikro-orm.io/docs/events#hooks) - [Schema Generator](https://mikro-orm.io/docs/schema-generator) and [Migrations](https://mikro-orm.io/docs/migrations) - [Entity Generator](https://mikro-orm.io/docs/entity-generator) and [Seeding](https://mikro-orm.io/docs/seeding) - [Embeddables](https://mikro-orm.io/docs/embeddables), [Custom Types](https://mikro-orm.io/docs/custom-types), and [Serialization](https://mikro-orm.io/docs/serializing) - [Composite and Foreign Keys as Primary Key](https://mikro-orm.io/docs/composite-keys) - [Entity Constructors](https://mikro-orm.io/docs/entity-constructors) and [Property Validation](https://mikro-orm.io/docs/property-validation) - [Modelling Relationships](https://mikro-orm.io/docs/relationships) and [Vanilla JS Support](https://mikro-orm.io/docs/usage-with-js) ## Documentation MikroORM documentation, included in this repo in the root directory, is built with [Docusaurus](https://docusaurus.io) and publicly hosted on GitHub Pages at https://mikro-orm.io. There is also auto-generated [CHANGELOG.md](CHANGELOG.md) file based on commit messages (via `semantic-release`). ## Example Integrations You can find example integrations for some popular frameworks in the [`mikro-orm-examples` repository](https://github.com/mikro-orm/mikro-orm-examples): ### TypeScript Examples - [Express + MongoDB](https://github.com/mikro-orm/express-ts-example-app) - [Nest + MySQL](https://github.com/mikro-orm/nestjs-example-app) - [RealWorld example app (Nest + MySQL)](https://github.com/mikro-orm/nestjs-realworld-example-app) - [Koa + SQLite](https://github.com/mikro-orm/koa-ts-example-app) - [GraphQL + PostgreSQL](https://github.com/driescroons/mikro-orm-graphql-example) - [Inversify + PostgreSQL](https://github.com/PodaruDragos/inversify-example-app) - [NextJS + MySQL](https://github.com/jonahallibone/mikro-orm-nextjs) - [Accounts.js REST and GraphQL authentication + SQLite](https://github.com/darkbasic/mikro-orm-accounts-example) - [Nest + Shopify + PostgreSQL + GraphQL](https://github.com/Cloudshelf/Shopify_CSConnector) - [Elysia.js + libSQL + Bun](https://github.com/mikro-orm/elysia-bun-example-app) - [Electron.js + PostgreSQL](https://github.com/adnanlah/electron-mikro-orm-example-app) ### JavaScript Examples - [Express + SQLite](https://github.com/mikro-orm/express-js-example-app) ## Contributing Contributions, issues and feature requests are welcome. Please read [CONTRIBUTING.md](CONTRIBUTING.md) for details on the process for submitting pull requests to us. ## Authors **Martin Adámek** - Twitter: [@B4nan](https://twitter.com/B4nan) - Github: [@b4nan](https://github.com/b4nan) See also the list of contributors who [participated](https://github.com/mikro-orm/mikro-orm/contributors) in this project. ## Show Your Support Please star this repository if this project helped you! > If you'd like to support my open-source work, consider sponsoring me directly at [github.com/sponsors/b4nan](https://github.com/sponsors/b4nan). ## License Copyright © 2018-present [Martin Adámek](https://github.com/b4nan). This project is licensed under the MIT License - see the [LICENSE file](LICENSE) for details.