Object-Relational Mapper

What Is an ORM?

How an ORM Works

1. Mapping Database Tables to Classes:
   • Each table in the database is represented as a class in the application.
   • Each column in the table becomes an attribute (field) of the class.
2. Mapping Rows to Objects:
   • Each row in the table becomes an instance of the mapped class.
3. CRUD Operations:
   • ORMs provide methods to perform Create, Read, Update, and Delete (CRUD) operations without requiring raw SQL. For example:
     • Create: Insert a new record into the database by creating an object and saving it.
     • Read: Query the database and retrieve rows that are automatically converted into objects.
     • Update: Modify an object and save it back to the database.
     • Delete: Remove a record by deleting the corresponding object.
4. Query Abstraction:
   • ORMs allow developers to write database queries in the application's programming language, often using objects and methods that abstract SQL syntax.

Why Are ORMs Important?

1. Reduced Complexity:
   • Developers can work with objects instead of learning and writing raw SQL, reducing the cognitive load and potential for errors.
2. Code Maintainability:
   • Query logic is embedded in the application code, making it easier to maintain and refactor.
3. Database Agnosticism:
   • Many ORMs support multiple database backends (e.g., PostgreSQL, MySQL, SQLite), making it easier to switch databases if needed.
4. Productivity:
   • ORMs automate repetitive tasks like mapping objects to tables, validation, and query generation, allowing developers to focus on business logic.
5. Security:
   • By abstracting queries, ORMs help prevent SQL injection vulnerabilities, as they often use parameterized queries under the hood.

1. SQLAlchemy (Python)

• What It Offers: A highly flexible and popular ORM for Python, offering both ORM and lower-level database interaction capabilities.
• Key Features:
  • Declarative ORM and Core SQL Expression Language.
  • Support for advanced queries, joins, and relationships.
  • Highly customizable for complex use cases.
• Use Case: Suitable for developers needing fine-grained control over database interactions.

2. Prisma (JavaScript/TypeScript)

• What It Offers: Prisma is a modern ORM for Node.js and TypeScript applications, offering type-safe database interactions.
• Key Features:
  • Auto-generated, strongly-typed database client.
  • Schema-driven development with Prisma Schema.
  • Database migrations support.
  • Works with multiple databases like PostgreSQL, MySQL, SQLite, and MongoDB.
• Use Case: Great for TypeScript developers building full-stack applications with modern tools like Next.js.

3. Hibernate (Java)

• What It Offers: A mature ORM for Java that implements the JPA (Java Persistence API) standard.
• Key Features:
  • Support for lazy loading, caching, and complex relationships.
  • Automatic SQL query generation.
  • Database-agnostic with support for multiple backends.
• Use Case: Widely used in enterprise-level applications requiring robust database interaction.

4. Entity Framework (C#/.NET)

• What It Offers: Microsoft's ORM for .NET applications, simplifying database access in C#.
• Key Features:
  • Strong integration with Visual Studio.
  • Support for LINQ (Language Integrated Query) to write queries using C# syntax.
  • Database-first and code-first approaches for schema management.
• Use Case: Ideal for .NET developers building enterprise or web applications.

5. Tortoise ORM (Python)

• What It Offers: A lightweight and asynchronous ORM designed for Python's async frameworks like FastAPI and Starlette.
• Key Features:
  • Fully asynchronous queries.
  • Support for multiple relational databases.
  • Simple and easy-to-learn API for rapid development.
• Use Case: Perfect for modern Python web applications that rely on async programming.

6. GORM (Go)

• What It Offers: A powerful and developer-friendly ORM for Go (Golang).
• Key Features:
  • Support for associations, hooks, and transactions.
  • Auto-migration to keep database schemas consistent.
  • Extensible API for customization.
• Use Case: Popular in Go-based microservices and APIs.

7. TypeORM (JavaScript/TypeScript)

• What It Offers: An ORM for JavaScript and TypeScript with support for multiple databases and a focus on flexibility.
• Key Features:
  • Database-agnostic with support for MySQL, PostgreSQL, SQLite, MongoDB, and more.
  • Active Record and Data Mapper patterns.
  • Built-in support for decorators in TypeScript.
• Use Case: Useful for full-stack TypeScript applications, especially those using frameworks like NestJS.

8. Objection.js (JavaScript)

• What It Offers: A lightweight ORM for Node.js built on top of Knex.js, combining the simplicity of SQL with the convenience of an ORM.
• Key Features:
  • Easy to use with advanced query-building capabilities.
  • Full support for relationships and eager loading.
  • Flexibility to use raw SQL when necessary.
• Use Case: Ideal for developers who need both control over raw SQL and the abstraction of an ORM.

Conclusion