Object Relational Mapping (ORM) is a technique used in creating a "bridge" between object-oriented programs and, in most cases, relational databases.

Put another way, you can see the ORM as the layer that connects object oriented programming (OOP) to relational databases.

When interacting with a database using OOP languages, you'll have to perform different operations like creating, reading, updating, and deleting (CRUD) data from a database. By design, you use SQL for performing these operations in relational databases.

While using SQL for this purpose isn't necessarily a bad idea, the ORM and ORM tools help simplify the interaction between relational databases and different OOP languages.

What is an ORM Tool?

An ORM tool is software designed to help OOP developers interact with relational databases. So instead of creating your own ORM software from scratch, you can make use of these tools.

Here's an example of SQL code that retrieves information about a particular user from a database:

"SELECT id, name, email, country, phone_number FROM users WHERE id = 20"

The code above returns information about a user — name, email, country, and phone_number — from a table called users. Using the WHERE clause, we specified that the information should be from a user with an id of 20.

On the other hand, an ORM tool can do the same query as above with simpler methods. That is:


So the code above does the same as the SQL query. Note that every ORM tool is built differently so the methods are never the same, but the general purpose is similar.

ORM tools can generate methods like the one in the last example.

Most OOP languages have a variety of ORM tools that you can choose from. Here are some of the most popular for Java, Python, PHP, and .NET development:

1. Hibernate

Hibernate enables developers to write data persistent classes following OOP concepts like inheritance, polymorphism, association, composition. Hibernate is highly performant and is also scalable.

2. Apache OpenJPA

Apache OpenJPA is also a Java persistence tool. It can be used as a stand-alone POJO (plain old Java object) persistence layer.

EclipseLink is an open source Java persistence solution for relational, XML, and database web services.

4. jOOQ

jOOQ generates Java code from data stored in a database. You can also use this tool to build type safe SQL queries.

You can use Oracle TopLink to build high-performance applications that store persistent data. The data can be transformed into either relational data or XML elements.

1. Django

Django is a great tool for building web applications rapidly.

2. web2py

web2py is an open source full-stack Python framework for building fast, scalable, secure, and data-driven web applications.

3. SQLObject

SQLObject is an object relational manager that provides an object interface to your database.

4. SQLAlchemy

SQLAlchemy provides persistence patterns designed for efficient and high-performing database access.

1. Laravel

Laravel comes with an object relational manager called Eloquent which makes interaction with databases easier.

2. CakePHP

CakePHP provides two object types: repositories which give you access to a collection of data and entities which represents individual records of data.

3. Qcodo

Qcodo provides different commands that can be run in the terminal to interact with databases.

4. RedBeanPHP

RedBeanPHP is a zero config object relational mapper.

1. Entity Framework

Entity Framework is a multi-database object-database mapper. It supports SQL, SQLite, MySQL, PostgreSQL, and Azure Cosmos DB.

2. NHibernate

NHibernate is an open source object relational mapper with tons of plugins and tools to make development easier and faster.

3. Dapper

Dapper is a micro-ORM. It is mainly used to map queries to objects. This tool doesn't do most of the things an ORM tool would do like SQL generation, caching results, lazy loading, and so on.

4. Base One Foundation Component Library (BFC)

BFC is a framework for creating networked database applications with Visual Studio and DBMS software from Microsoft, Oracle, IBM, Sybase, and MySQL

You can see more ORM tools here.

Now let's discuss some of the advantages and disadvantages of using ORM tools.

Advantages of Using ORM Tools

Here are some of the advantages of using an ORM tool:

  • It speeds up development time for teams.
  • Decreases the cost of development.
  • Handles the logic required to interact with databases.
  • Improves security. ORM tools are built to eliminate the possibility of SQL injection attacks.
  • You write less code when using ORM tools than with SQL.

Disadvantages of Using ORM Tools

  • Learning how to use ORM tools can be time consuming.
  • They are likely not going to perform better when very complex queries are involved.
  • ORMs are generally slower than using SQL.


In this article, we talked about Object Relational Mapping. This is a technique used to connect object oriented programs to relational databases.

We listed some of the popular ORM tools for different programming languages.

We concluded with some of the advantages and disadvantages of using ORM tools. languages.

Happy coding!