Lookup vs Master-Detail Relationship in Salesforce

When working with Salesforce, you often need to connect records from different objects. For example, you may want to connect a Student with a Course, an Employee with a Department, or an Invoice with its Invoice Items.

Salesforce provides different types of relationships to connect objects. Two of the most important are:

• Lookup Relationship
• Master-Detail Relationship

Although both connect two objects, they behave very differently.

What Is a Lookup Relationship in Salesforce?

A Lookup Relationship creates a relatively loose relationship between two objects.

The child record can generally exist independently of the parent record.

Example

Suppose we have two objects:

Student → Course

A Student record can contain a lookup field that points to a Course.

For example:

Student Name: Rahul
Course: Salesforce Admin

Here, the Student is connected to the Course, but the Student record can still have its own ownership and security.

Key Features of a Lookup Relationship

• Creates a flexible relationship between objects.
• Child records can generally exist independently.
• Parent and child can have separate ownership.
• Security settings can be managed independently.
• Deleting the parent doesn’t normally delete the child records.
• Useful when records need to be connected without creating strong dependency.

What Is a Master-Detail Relationship in Salesforce?

A Master-Detail Relationship creates a strong parent-child relationship between two objects.

The parent is called the Master, while the child is called the Detail.

The detail record depends on the master record.

Example

Consider:

Invoice → Invoice Item

The Invoice is the Master record.

The Invoice Item is the Detail record.

An Invoice Item belongs to a specific Invoice and does not operate independently in the same way as a lookup-related record.

Key Features of a Master-Detail Relationship

• Creates a strong relationship between two objects.
• The detail record depends on the master record.
• The detail record inherits ownership and sharing behavior from the master.
• Deleting the master also deletes its detail records.
• Supports Roll-Up Summary fields on the master.
• Useful when the child logically belongs to the parent.

Lookup vs Master-Detail Relationship

Feature	Lookup Relationship	Master-Detail Relationship
Relationship Type	Loose	Strong
Child Dependency	More independent	Dependent on master
Ownership	Can have separate ownership	Controlled by master
Security	Can be independent	Inherited from master
Parent Deletion	Child normally remains	Detail records are deleted
Roll-Up Summary	Not directly supported	Supported
Best For	Flexible connections	Strong parent-child structures

Roll-Up Summary: An Important Difference

One of the biggest advantages of a Master-Detail Relationship is support for Roll-Up Summary Fields.

A Roll-Up Summary field allows the master record to calculate information from its related detail records.

For example, suppose:

Invoice A has three Invoice Items:

Item 1 = ₹5,000
Item 2 = ₹3,000
Item 3 = ₹2,000

A Roll-Up Summary field on the Invoice could calculate:

Total Invoice Value = ₹10,000

Common roll-up operations include:

• COUNT
• SUM
• MIN
• MAX

Standard Lookup Relationships do not directly provide native Roll-Up Summary fields in the same way.

When Should You Use a Lookup Relationship?

Use a Lookup Relationship when the records need to be connected but should retain more independence.

Examples include:

Employee → Department

An employee may be associated with a department, but the employee is still an independent record.

Another example could be:

Student → Course

A student can be associated with a course without requiring the same strong dependency as a Master-Detail Relationship.

When Should You Use a Master-Detail Relationship?

Use a Master-Detail Relationship when the child record logically depends on its parent.

For example:

Invoice → Invoice Item

An Invoice Item makes sense