B4nan

await orm.em.transactional(async _em => {
  //... do some work
  const user = new User(...);
  user.name = 'George';
  _em.persistLater(user);
});

B4nan

await orm.em.beginTransaction();

try {
  //... do some work
  const user = new User(...);
  user.name = 'George';
  await orm.em.persistAndFlush(user);
  await orm.em.commit();
} catch (e) {
  await orm.em.rollback();

B4nan

START TRANSACTION;
INSERT INTO `book_tag` (`name`) VALUES (?);
UPDATE `book` SET `title` = ? WHERE `id` = ?;
DELETE FROM `book_to_book_tag` WHERE `book_id` = ?;
INSERT INTO `book_to_book_tag` (`book_id`, `book_tag_id`) VALUES (?, ?);
INSERT INTO `book_to_book_tag` (`book_id`, `book_tag_id`) VALUES (?, ?);
UPDATE `publisher` SET `name` = ? WHERE `id` = ?;
UPDATE `book_tag` SET `name` = ? WHERE `id` = ?;
COMMIT;

B4nan

const author = await orm.em.findOne(Author, id, ['books.tags', 'books.publisher']);
author.books[0].title = 'New book name';
author.books[0].tags[0].name = 'old';
author.books[0].tags.add(new BookTag('sale'));
author.books[0].publisher.name = 'New publisher name';
await orm.em.flush();

B4nan

const user = new User();
user.name = 'George';
await orm.em.persistAndFlush(user);

B4nan

// find author and populate his books collection
const author = orm.em.findOne(Author, '...', ['books']);

for (const book of author.books) {
  console.log(book); // instance of Book
}

author.books.add(book);
console.log(author.books.contains(book)); // true
author.books.remove(book);

B4nan

import { QueryOrder } from 'mikro-orm';

const booksRepository = orm.em.getRepository(Book);

// with sorting, limit and offset parameters, populating author references
const books = await booksRepository.find({ author: '...' }, ['author'], { title: QueryOrder.DESC }, 2, 1);

// or with options object
const books = await booksRepository.find({ author: '...' }, { 
  populate: ['author'],

B4nan

const book = orm.em.findOne(Book, '...');
console.log(book.author); // reference with ID only, instance of Author entity

// this will get the same reference as we already have in `book.author`
const author = orm.em.getReference(Author, book.author.id);
console.log(author.id); // accessing the id will not trigger any db call
console.log(author.isInitialized()); // false
console.log(author.name); // undefined
console.log(author === book.author); // true

B4nan

const authorRepository = orm.em.getRepository(Author);
const jon = await authorRepository.findOne({ name: 'Jon Snow' }, ['books']);
const jon2 = await authorRepository.findOne({ email: '[email protected]' });
const authors = await authorRepository.findAll(['books']);

// identity map in action
console.log(jon === authors[0]); // true
console.log(jon === jon2); // true

// as we always have one instance, books will be populated also here

B4nan

# using yarn
$ yarn add mikro-orm mongodb # for mongo
$ yarn add mikro-orm mysql2  # for mysql
$ yarn add mikro-orm pg      # for postgresql
$ yarn add mikro-orm sqlite  # for sqlite

# or npm
$ npm i -s mikro-orm mongodb # for mongo
$ npm i -s mikro-orm mysql2  # for mysql
$ npm i -s mikro-orm pg      # for postgresql