Many-to-Many Relationships in Salesforce (Using Junction Objects)

When working with Salesforce, you’ll often encounter situations where a record in one object needs to be associated with multiple records in another object, and vice versa. This is where Many-to-Many relationships come into play.

In this blog, we’ll explore:

What Many-to-Many Relationships are
Why we need them
How to implement them using Junction Objects
A practical real-world example
Diagram to visualize the relationship

1. What is a Many-to-Many Relationship?

A Many-to-Many relationship means that:

One record from Object A can be related to multiple records in Object B.
At the same time, one record from Object B can be related to multiple records in Object A.

👉 Example:

A Student can enroll in multiple Courses.
A Course can have multiple Students enrolled.

Clearly, a direct relationship is not enough — we need a bridge between them. That’s where Junction Objects help.

2. Why Do We Need a Junction Object?

Salesforce doesn’t provide a direct “Many-to-Many” relationship type. Instead, we achieve it by creating a Junction Object, which acts as a bridge between two objects.

The Junction Object contains two Master-Detail or Lookup Relationships pointing to the two objects we want to connect.

This way:

The Junction Object becomes the linking record.
Each record in the Junction Object represents one association between Object A and Object B.

3. How to Create a Many-to-Many Relationship (Step by Step)

Let’s implement the Student ↔ Course example:

Step 1: Identify the Objects

Student (Custom Object)
Course (Custom Object)

Step 2: Create a Junction Object

Create a custom object called Enrollment (this will act as the bridge).

Step 3: Add Master-Detail Relationships

On Enrollment, create a Master-Detail relationship to Student.
On Enrollment, create another Master-Detail relationship to Course.

Step 4: Result

Now:

A Student can have multiple Enrollments.
A Course can have multiple Enrollments.
Each Enrollment record links one Student with one Course.

4. Real-World Example

Here are a few real-world scenarios where Many-to-Many relationships are useful:

Students ↔ Courses (Education system)
Doctors ↔ Patients (Healthcare system)
Products ↔ Orders (E-commerce)
Employees ↔ Projects (Work management)

5. Diagram of Many-to-Many Relationship

Student ↔ Enrollment = One-to-Many
Course ↔ Enrollment = One-to-Many
Combined → Many-to-Many (Student ↔ Course)

6. Benefits of Using Junction Objects

Handles complex relationships easily.
Provides scalability for real-world scenarios.
Enables custom fields on the junction (like “Enrollment Date” or “Role in Project”).
Supports reporting across multiple objects.

7. Key Takeaways

Salesforce doesn’t allow a direct Many-to-Many relationship
We achieve it using a Junction Object with two Master-Detail or Lookup relationships
Junction Objects allow us to store additional information about the relationship itself
Common in real-world use cases like Students & Courses, Employees & Projects, etc.

🔥 Pro Tip:
If you want more flexibility, you can also use Lookup relationships instead of Master-Detail when creating the Junction Object, depending on your business needs.