# Relationship types: sharing, deletion and report types

*Platform App Builder Study Guide · Data Modeling and Management · Last updated October 25, 2026 · https://www.certifyforce.com/study-guide/platform-app-builder/data-modeling-and-management/relationship-types-sharing-deletion-and-report-types*

What lookup, master-detail, many-to-many, external lookup and indirect lookup relationships do to record access, deletion and undelete, page layouts and standard report types, and what changes when you convert a lookup to master-detail or back.

- Certification: Salesforce Platform App Builder
- Exam section: Data Modeling and Management
- Study guide: https://www.certifyforce.com/study-guide/platform-app-builder

**Official exam objective:**

> Given a scenario, explain the capabilities of the various relationship types and the implications of each on record access, user interface, and reporting.

## What the exam expects

- Compare lookup and master-detail on ownership, access, deletion and layouts.
- Predict access to detail and junction records.
- Predict delete and undelete results.
- Explain what converting a relationship does to sharing, data and reports.
- Pick the standard report type a relationship provides, and explain external and indirect lookups.

Key terms:
- **Controlled by Parent:** the sharing default of a detail object; access comes from the master record.
- **Sharing Setting:** the master access (Read Only or Read/Write) needed to create, edit or delete details.
- **Primary master:** the first master-detail relationship created on a junction object.
- **External lookup:** links a child to a parent external object by its External ID standard field.
- **Indirect lookup:** links a child external object to a standard or custom parent by a custom unique External ID field.

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Relationship limits | 2 master-detail; 40 total by default, up to 50 on request | [Maximum Relationships](https://help.salesforce.com/s/articleView?id=000386135&language=en_US&type=1) |
| Detail ownership | No Owner field; no sharing rules, manual sharing or queues | [Relationships Overview](https://help.salesforce.com/s/articleView?id=platform.overview_of_custom_object_relationships.htm&type=5) |
| Master-detail field on layout | Always required on the detail page layout | [Relationships Overview](https://help.salesforce.com/s/articleView?id=platform.overview_of_custom_object_relationships.htm&type=5) |
| Separately deleted detail | Can't be undeleted after its master is deleted | [Relationship Considerations](https://help.salesforce.com/s/articleView?id=platform.relationships_considerations.htm&type=5) |
| Delete this record also | Disabled by default; bypasses security and sharing | [Relationships Overview](https://help.salesforce.com/s/articleView?id=platform.overview_of_custom_object_relationships.htm&type=5) |
| Junction, both masters deleted | Junction record deleted permanently | [Relationship Considerations](https://help.salesforce.com/s/articleView?id=platform.relationships_considerations.htm&type=5) |
| Junction delete limit | Over 200 junction records plus a roll-up to the other parent blocks deleting a parent | [Relationship Considerations](https://help.salesforce.com/s/articleView?id=platform.relationships_considerations.htm&type=5) |
| Master-detail to lookup | Needs no roll-ups on the master; detail default becomes Public Read/Write | [Relationship Considerations](https://help.salesforce.com/s/articleView?id=platform.relationships_considerations.htm&type=5) |
| Lookup to master-detail | Every record needs a value; default becomes Controlled by Parent | [Relationship Considerations](https://help.salesforce.com/s/articleView?id=platform.relationships_considerations.htm&type=5) |

## Check yourself

- Why can't a detail object use sharing rules or queues?
- When does deleting a parent of a junction object fail?
- Why might an object not appear as a parent for an indirect lookup?

## Sources

- [Considerations for Object Relationships](https://help.salesforce.com/s/articleView?id=platform.relationships_considerations.htm&type=5)
- [Object Relationships Overview](https://help.salesforce.com/s/articleView?id=platform.overview_of_custom_object_relationships.htm&type=5)
- [Create a Many-to-Many Object Relationship](https://help.salesforce.com/s/articleView?id=platform.relationships_manytomany.htm&type=5)
- [External Object Relationships](https://help.salesforce.com/s/articleView?id=platform.external_object_relationships.htm&type=5)
- [Roll-Up Summary Field](https://help.salesforce.com/s/articleView?id=platform.fields_about_roll_up_summary_fields.htm&type=5)
- [Increase the maximum relationships (master-detail plus lookup) allowed per object](https://help.salesforce.com/s/articleView?id=000386135&language=en_US&type=1)
- [Create Object Relationships](https://trailhead.salesforce.com/content/learn/modules/data_modeling/object_relationships)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 16 linked practice questions, and unlimited timed mock exams are included with the Platform App Builder pack (USD $19): https://www.certifyforce.com/practice-exams