How to manage relation fields in Strapi CMS?

The content type builder empowers you to establish connections between different collection types through a feature called the "Relation field". This functionality allows you to link one or multiple data points from one content type to relevant attributes within another, creating intricate and dynamic relationships between your content models.

There are types of relationships we can establish in Strapi:

• One-to-One (1:1)
• One-to-Many
• Many-to-Many
• One-Way
• Many-Way
• Polymorphic

1. One-to-One (1:1) 

In a one-to-one (1:1) relationship, a column in one table references exactly one column in another table.

 For example, in a Student table, a “studentId” column can reference a unique record in a “StudentInfo” table. Similarly, a “studentId” column in the “StudentInfo” table can reference a unique record in the Student table. This establishes a one-to-one relationship, where each student record in one table is associated with exactly one record in the other table. As a result, you can retrieve student information from either table.

2. One-to-Many

In a one-to-many relationship, a column in one table (Table A) can reference multiple records in one or more other tables (Table B, Table C, Table D, Table E). Conversely, each record in these other tables references a single record in Table A.

For example,consider a company table containing a list of all companies in a system. An Employee table can store the names of employees, and a "companyId" column in the Employee table can reference a specific company in the company table.

This establishes a one-to-many relationship: a single company record in the company table can be associated with many employee records in the Employee table, while each employee record is linked to only one company record.

3. Many-to-Many

A many-to-many relationship occurs when a column in one table can reference multiple records in another table, and vice versa.

To use relation fields in Strapi CMS, follow these steps:

Step 1: Create Content Types

Begin by creating the content types you wish to establish relationships between. For instance, if you intend to create a relationship between "Authors" and "Books," you would need to create content types for both "Authors" and "Books."

Step 2: Define the Relation Field

• Access the Strapi admin panel.
• Navigate to the content type where you want to add the relation field. In our example, let's assume you're working with the "Books" content type.
• Click on "Content-Types Builder" and open the left sidebar.
• Select the "Books" content type.
• In the "Books" content type builder, create a new field that represents the relationship. This field can be of the "Relation" type.

Step 3: Configure the Relation Field

When creating the Relation field, you'll need to specify the target content type to which you want to establish a relationship. In this case, it would be the "Authors" content type. /p>

Choose the desired relationship type:

• For a one-to-one relationship, select "Single relation."
• For a one-to-many relationship, choose "Many relations."
• For a many-to-many relationship, select "Many relations" and enable the "Many-to-many" option.

Configure other options as needed, such as whether a relationship is required or not.

Step 4: Save Changes

After configuring the relation field, save your changes to the content type.

Step 5: Populate Content

Now that you've defined the relation field, you can begin creating or editing content. When you create or edit a "Book" entry, use the relation field to associate it with one or more "Authors" by selecting from the available options.

Step 6: Query and Access Related Data

In your Strapi API, you can query related data using GraphQL or REST API endpoints. When querying a "Book" entry, you can retrieve associated data from the "Authors" content type, and vice versa.

Here's a simplified example of querying related data using GraphQL:

In this query, we're retrieving a list of books and their associated authors' names.

Conclusion

The relation field in Strapi CMS offers a powerful tool for establishing connections between different content types. By understanding the various types of relationships—one-to-one, one-to-many, many-to-many, one-way, many-way, and polymorphic—you can create complex and dynamic content models.

Following the step-by-step process outlined in this blog, you can effectively define and configure relation fields to connect your data. This enables you to retrieve related information through GraphQL or REST API endpoints, enhancing the flexibility and richness of your content.

Remember to consult the official Strapi documentation for the most accurate and up-to-date information on relation fields. With a solid understanding of this feature, you can leverage Strapi's capabilities to build robust and interconnected content management systems.