# Relationship types, deletion options and custom metadata types

*Platform Data Architect Study Guide · Data Modeling/Database Design · Last updated October 26, 2026 · https://www.certifyforce.com/study-guide/platform-data-architect/data-modeling-database-design/relationship-types-deletion-options-and-custom-metadata-types*

How to choose between master-detail, lookup, junction, self and hierarchical relationships from ownership, deletion, roll-up and limit requirements, when record types beat separate objects, and why custom metadata types hold deployable configuration.

- Certification: Salesforce Platform Data Architect
- Exam section: Data Modeling/Database Design
- Study guide: https://www.certifyforce.com/study-guide/platform-data-architect

**Official exam objective:**

> Compare and contrast various techniques and considerations for designing a data model for the Customer 360 Platform (for example, objects, fields & relationships, object features).

## What the exam expects

- Choose master-detail or lookup from ownership, sharing, deletion and roll-up requirements.
- Model many-to-many with a junction, self-references with a lookup, and user chains with a hierarchical relationship.
- Pick the lookup deletion option (clear, block, cascade) and spot the 100,000-record and relationship-count limits before build.
- Place leads, opportunities, products, price books, quotes, orders, assets, entitlements and cases in the standard Sales and Service model, and pick record types or separate objects.
- Recommend custom metadata types for configuration that must be deployed, packaged and referenced by formulas and Apex.

Key terms: **master-detail** (the parent controls the child's owner, security and deletion); **lookup** (a loose link with its own owner and no native roll-ups); **junction object** (a custom object with two master-detail relationships); **cascade-delete** (Delete this record also on a lookup); **custom metadata type** (deployable, packageable application metadata).

Guide map: where each information-architecture building block of the [Exam Guide](https://help.salesforce.com/s/articleView?id=005298972&language=en_US&type=1) is taught:

| Building block | Unit |
|---|---|
| Data sourcing | "Single customer view: person accounts and identity resolution" |
| Integration/movement | "LDV load performance: Bulk API and sharing deferral" |
| Persistence | "Consistent writes: transactions, locking and upsert keys" |
| Master data management | "MDM styles, matching, enrichment and canonical models" |
| Metadata management | "Business and technical metadata: classification and lineage" |
| Semantic reconciliation | "Survivorship rules for winning attribute values" |
| Data governance | "Data governance programs: roles, stewardship and controls" |
| Security | "Record access design: OWDs, hierarchies and territories" |
| Delivery | "Virtualized data with Salesforce Connect external objects" |

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Master-detail per custom object | Up to 2 | [Relationships Overview](https://help.salesforce.com/s/articleView?id=overview_of_custom_object_relationships.htm&language=en_US&type=5) |
| Total relationships per object | 40 by default, hard maximum 50 by request | [Relationship limit](https://help.salesforce.com/s/articleView?id=000386135&language=en_US&type=1) |
| Custom detail depth | Up to 3 custom detail levels | [Relationship Considerations](https://help.salesforce.com/s/articleView?id=relationships_considerations.htm&language=en_US&type=5) |
| Children per master | Best practice: no more than 10,000 | [Relationships Overview](https://help.salesforce.com/s/articleView?id=overview_of_custom_object_relationships.htm&language=en_US&type=5) |
| Roll-up summary fields | Master-detail only; use a flow on lookups | [Roll-ups with Flow](https://help.salesforce.com/s/articleView?id=002722670&language=en_US&type=1) |
| Optional lookup default on parent delete | Clear the value of this field | [Relationships Overview](https://help.salesforce.com/s/articleView?id=overview_of_custom_object_relationships.htm&language=en_US&type=5) |
| Cascade-delete | Disabled by default; Salesforce enables it; bypasses sharing | [Relationship Considerations](https://help.salesforce.com/s/articleView?id=relationships_considerations.htm&language=en_US&type=5) |
| Lookup delete blocked | Combined records across both objects over 100,000 | [Relationships Overview](https://help.salesforce.com/s/articleView?id=overview_of_custom_object_relationships.htm&language=en_US&type=5) |
| Custom metadata deployment | Change sets and packages | [Custom Metadata Types](https://help.salesforce.com/s/articleView?id=platform.custommetadatatypes_overview.htm&type=5) |

## Check yourself

- Why can't a custom object on the detail side of a master-detail relationship be routed to a queue?
- When does deleting a lookup parent fail even though the user has full object permissions?
- Why should a custom metadata type reference fields through Field Definition relationships rather than text?

## Sources

- [Object Relationships Overview](https://help.salesforce.com/s/articleView?id=overview_of_custom_object_relationships.htm&language=en_US&type=5)
- [Considerations for Object Relationships](https://help.salesforce.com/s/articleView?id=relationships_considerations.htm&language=en_US&type=5)
- [Create a Many-to-Many Object Relationship](https://help.salesforce.com/s/articleView?id=platform.relationships_manytomany.htm&language=en_US&type=5)
- [Increase the maximum relationships allowed per object](https://help.salesforce.com/s/articleView?id=000386135&language=en_US&type=1)
- [Create Roll-Up Summary Fields Utilizing Salesforce Flow](https://help.salesforce.com/s/articleView?id=002722670&language=en_US&type=1)
- [Custom Metadata Types](https://help.salesforce.com/s/articleView?id=platform.custommetadatatypes_overview.htm&type=5)
- [Tailor Business Processes to Different Record Types Users](https://help.salesforce.com/s/articleView?id=platform.customize_recordtype.htm&type=5)
- [Optimize Customer Data with Objects](https://trailhead.salesforce.com/content/learn/modules/data_modeling/objects_intro)
- [Convert Qualified Leads](https://help.salesforce.com/s/articleView?id=sales.leads_convert.htm&type=5)
- [Case (Object Reference)](https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_case.htm)
- [Salesforce Certified Platform Data Architect Exam Guide](https://help.salesforce.com/s/articleView?id=005298972&language=en_US&type=1)
- [Learn About, Implement, and Optimize Sales Features](https://help.salesforce.com/s/articleView?id=sales.sales_core_basics.htm&language=en_US&type=5)
- [PricebookEntry (Object Reference)](https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_pricebookentry.htm)
- [OpportunityLineItem (Object Reference)](https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_opportunitylineitem.htm)
- [Quotes](https://help.salesforce.com/s/articleView?id=sf.quotes_overview.htm&type=5)
- [Orders](https://help.salesforce.com/s/articleView?id=sales.order_overview.htm&language=en_US&type=5)
- [Asset (Object Reference)](https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_asset.htm)
- [Entitlement (Object Reference)](https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_entitlement.htm)
- [What's Entitlement Management?](https://help.salesforce.com/s/articleView?id=service.entitlements_about.htm&language=en_US&type=5)
- [Trailhead: Use Entitlements in Customer Cases](https://trailhead.salesforce.com/content/learn/modules/entitlement-management-for-lightning-experience/use-entitlements-in-customer-cases)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 17 linked practice questions, and unlimited timed mock exams are included with the Platform Data Architect pack (USD $19): https://www.certifyforce.com/practice-exams