api-database-typeorm

Database with TypeORM

Quick Guide: Use TypeORM for decorator-based database access with full TypeScript support. Schema defined via entity classes with @Entity, @Column, @PrimaryGeneratedColumn. Use Data Mapper pattern (repositories) over Active Record for non-trivial apps. Never use synchronize: true in production - use migrations. Prefer insert()/update() over save() when you know the operation type - save() always executes a SELECT first. Use QueryRunner transactions for full control. Eager relations only work with find* methods, not QueryBuilder.

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<critical_requirements>

CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering, import type, named constants)

(You MUST NEVER use synchronize: true in production - it can drop columns and lose data when entities change)

(You MUST use insert()/update() instead of save() when the operation type is known - save() always runs an extra SELECT query)

(You MUST use the provided transaction manager parameter or queryRunner.manager inside transactions - NEVER use the global entity manager or repository)

(You MUST define relations with explicit @JoinColumn() on the owning side of @OneToOne and optionally @ManyToOne, and @JoinTable() on one side of @ManyToMany)

</critical_requirements>

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Auto-detection: typeorm, TypeORM, DataSource, @Entity, @Column, @PrimaryGeneratedColumn, @ManyToOne, @OneToMany, @ManyToMany, createQueryBuilder, getRepository, EntityManager, QueryRunner, migration:generate, migration:run

When to use:

• Decorator-based entity definitions with TypeScript
• Applications requiring both Active Record and Data Mapper patterns
• Complex queries needing QueryBuilder with joins and subqueries
• Projects where class-based ORM feels natural (especially with DI-based frameworks)

When NOT to use:

• Schema-first workflows (consider schema-first ORMs instead)
• Needing fully type-safe queries without runtime decorators (consider lighter ORMs)
• Edge/serverless with minimal cold start (decorator metadata adds weight)
• Projects avoiding reflect-metadata and experimentalDecorators