Modern applications are becoming increasingly complex. Business logic evolves rapidly, while databases remain centered around relational structures. Bridging the gap between these two with direct SQL each time presents limitations in productivity and maintainability. Object-Relational Mapping (ORM) emerged to bridge this gap, and it continues to play a crucial role in many systems.

The concept of ORM

ORM is a technology that automatically maps objects in object-oriented languages ​​to tables in relational databases. Developers can query, store, and modify database data as if they were objects, without having to write SQL directly.

The core purposes of ORM are:

• Abstracts database access logic.
• Connects object-oriented design and data storage structures.
• Reduces writing repetitive CRUD code.

Key Use Cases for ORM

1. Web application backend development

ORM is most widely used in server-side web service development. Domain models such as users, orders, products, and posts are defined as objects, allowing them to be seamlessly connected to a database. In this case, ORM performs the following roles:

• Entity-based data modeling
• Separation of business logic and data access logic
• Track and automatically reflect data changes

2. Rapid service development and maintenance

ORMs significantly accelerate initial development. They reduce the burden of writing SQL, and the scope of code modifications when the database schema changes is relatively clear. They are particularly beneficial in the following situations:

• MVP development
• Frequent changes in requirements
• Team-based collaboration environment

3. Ensuring database independence

Using an ORM reduces dependency on a specific database vendor. It becomes relatively easy to replace or run parallel databases while maintaining the same code structure. This provides the following long-term benefits:

• Flexibility to change infrastructure
• Separation of test and production environments
• Reduced burden when migrating to the cloud

Limitations and Cautions of ORM

1. Possible performance issues

Instead of providing an abstraction layer, ORMs make it difficult for developers to understand what SQL their code actually translates to. This can lead to inefficient queries or unnecessary data retrieval. This problem is particularly evident in the following cases:

• Large-scale data query
• Complex join queries
• Performance-sensitive transaction processing

2. Excessive reliance on ORM

Using an ORM doesn't mean database design is unimportant. In fact, poorly designed table structures can quickly propagate problems through ORM. ORM isn't a replacement for SQL, but rather a tool for writing better SQL.

3. Limitations of complex query expressions

Complex statistical queries or specialized data processing logic can be difficult to express in ORM syntax or significantly reduce readability. In these cases, native SQL must be used in parallel. This can lead to the following problems:

• Mixing ORM code and SQL code
• Inconsistent data access
• Increased maintenance complexity

Development direction of ORM technology

1. Strengthening coexistence of ORM and SQL

Recent ORMs are focusing on "enabling control of SQL." This is why query builders, native query support, and query execution logging are being enhanced. This means ORMs are evolving from being all-purpose tools to hybrid data access layers.

2. Enhanced type safety and static analysis

With the proliferation of type-centric languages ​​like TypeScript, Kotlin, and Rust, ORMs are also evolving to enhance type safety. Efforts are increasing to reduce errors during compilation and proactively detect query errors at the IDE level.

3. Integration with domain-centric design

ORMs are moving beyond simple data access tools and are becoming more deeply integrated with domain-driven design. This shift is toward supporting business concept-driven design, rather than database-centric design.

Insight Summary

• ORM is an abstraction layer that connects objects and relational databases.
• It greatly improves development productivity and maintainability.
• There are limitations in performance and complex queries.
• ORM is not a technology that replaces SQL, but rather a technology that complements it.
• The ORM of the future is evolving to be hybrid, type-safe, and domain-centric.