---
title: Predefined Relations
slug: segment/predefined-relations
createdAt: 2026-01-17T15:34:16.010Z
---

You can predefine the relations between your Data Extensions. You can take advantage of these Predefined Relations when combining Data Extensions in your Selected Data Extensions area, when creating *In/Not In Results* filters, and when using Aggregations custom value.

## Video example

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## How it works

Predefined relations serve as the structural foundation for efficient segmentation by establishing permanent, reusable links between disparate tables. These relations are defined as saved links between two **Data Extensions** or system **Data Views**. To establish a technical link, you must identify matching columns between the data sources and define a relationship type, specifically *one-to-one* or *one-to-many*.

Predefined relations bring different advantages:

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**Automated joins**: You eliminate the need for manual join configuration during the selection process because established paths between tables are recognized automatically.
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**Improved In/Not In Results filters**: The **Related Records** panel provides increased precision when filtering, allowing you to use established relations to refine exclusion and inclusion logic.
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**Improved aggregations**: You can utilize **Basic Mode** for aggregation functions such as **SUM**, **AVG**, **COUNT**, **MIN**, and **MAX**, which requires a predefined relation to perform calculations.
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**Data Sets**: These relations permit the creation of pre-configured groups of **Data Extensions**. This enables you to pull in a pre-validated star schema with a single action, allowing users to leverage complex data architectures without manual reconstruction.
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Setting up predefined relations during onboarding reduces the probability of configuration errors.
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## Set up predefined relations

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You need to be an admin to apply this configuration.
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Administrative precision during the setup phase is critical to preventing downstream data discrepancies. Incorrectly mapped relations can lead to inaccurate segment counts or missing data in your target results, making the initial configuration a vital step for maintaining data quality.
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1. Navigate to the **Admin Panel** and select the **Relations** option on the sidebar.
2. Click the **New Relation** button to initiate the configuration.
3. Use the first dropdown labeled **Data Extension** to select the primary source, such as *DESelect\_DEMO\_Customers*, and use the **Field** dropdown to select the matching identifier, such as *Id*.
4. Choose the relationship type from the **Has a** dropdown (e.g., *1-many*), then select the second source from the **Relation With** dropdown (e.g., *DESelect\_DEMO\_Orders*) and its corresponding **Field** (e.g., *CustomerId*).

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5. Click the **Add Relationship** button if multiple mappings are required to establish a unique link.

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There is no limit on the number of relations you can predefine between Data Extensions.
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6. Click the **Save** button to finalize the relation and view it on the overview page.