Handle One-to-One and One-to-Many Relationships

Overview

In this lesson, we’ll delve into the intricacies of one-to-one and one-to-many relationships and learn how to manage them with TypeORM.

Relationships are the associations between different entities (tables) in a relational database. There are several types of relationships.

• One-to-one (1:1): One record in a table is related to one—and only one—record in another. For example, a user and their primary address have a one-to-one relationship.

• One-to-many (1:N): A record in one table can be related to multiple records in another. For instance, a single user might have multiple posts in a blogging application.

• Many-to-many (N:N): Multiple records in one table can be related to multiple records in another. For instance, students and courses in a school management system might have a many-to-many relationship.

Handling a one-to-one relationship

The following illustration shows a one-to-one relationship between the address and user tables. An address is linked to one user, and each user has only one primary address.

In the example above, we focused on scenarios where each entity on one side—for example, User—is associated with exactly one entity on the other side—for example, Address. However, it’s worth noting that we ...