TypeORM Data Mapper Entities & Complex Relations

---
name: "typeorm-data-mapper-entities"
description: "Build enterprise TypeScript applications using TypeORM Data Mapper patterns and entities."
metadata:
  author: "TypeORM"
  version: "1.0.0"
  runtime_compatibility:
    - "codex"
    - "claude-code"
    - "cursor"
    - "windsurf"
triggers:
  - "create typeorm entity"
  - "typeorm querybuilder join"
  - "initialize typeorm datasource"
permissions:
  fs_read: true
  fs_write: "workspace"
  shell_exec: false
  net_access: false
---

# TypeORM Data Mapper Entities & Complex Relations

Implements TypeORM: @Entity decorators, @Column types, relations (@OneToMany, @ManyToMany with join tables), DataSource initialization, writing complex queries with QueryBuilder, and migration files.

## When to Invoke
Invoke this skill whenever you need to:
- create typeorm entity
- typeorm querybuilder join
- initialize typeorm datasource

## Execution SOP & Rules
1. Define entities using @Entity() and declare typed columns with @PrimaryGeneratedColumn() and @Column().
2. Use the Data Mapper pattern via repository: const userRepo = AppDataSource.getRepository(User).
3. Construct complex queries: userRepo.createQueryBuilder('user').leftJoinAndSelect('user.roles', 'role').where('user.active = :active', { active: true }).getMany().
4. Manage schema versioning via TypeORM CLI migration commands.

## Verification Checklist
- Run local linting, syntax validation, and type-checks before reporting completion.
- Ensure all created or modified files adhere to workspace boundaries and avoid uncommitted secrets.
- Verify tests or build commands exit cleanly with return code 0.