What is the difference between find(), findOne(), findOneOrFail(), and the Query Builder in TypeORM?

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Accepted Answer

// find() — returns array, empty array if nothing matches
const users = await this.userRepo.find({ where: { isActive: true } });

// findOne() — returns entity or null
const user = await this.userRepo.findOne({ where: { id } });
if (!user) throw new NotFoundException();

// findOneOrFail() — throws EntityNotFoundError if not found
// map to NotFoundException in a global filter
const user = await this.userRepo.findOneOrFail({ where: { id } });

// findAndCount() — returns [entities, total] for pagination
const [users, total] = await this.userRepo.findAndCount({
  skip: (page - 1) * limit,
  take: limit,
  order: { createdAt: 'DESC' },
});

// QueryBuilder — complex queries, joins, subqueries
const users = await this.userRepo
  .createQueryBuilder('user')
  .leftJoinAndSelect('user.posts', 'post')
  .where('user.isActive = :active', { active: true })
  .andWhere('post.publishedAt IS NOT NULL')
  .orderBy('user.createdAt', 'DESC')
  .skip(skip).take(limit)
  .getMany(); find() — simple list queries with where, order, relations, skip, take options. findOne() — fetch a single entity; always check for null before using the result. findOneOrFail() — when not finding the entity is an error; map EntityNotFoundError to NotFoundException. findAndCount() — pagination; returns count without a second query. QueryBuilder — complex joins, subqueries, raw expressions, conditional where clauses, and aggregations.

What is the difference between find(), findOne(), findOneOrFail(), and the Query Builder in TypeORM?

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