---
schema_version: "1"
id: 49d60942e0a5c9c9b5332b24b7367f655544a3a81b87cd6fc77829d7bc03ff50
title: Link Data Extensions in Contact Builder
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/mktg/264-0-0/mc_cab_link_data_extensions.md
canonical_url: https://help.salesforce.com/s/articleView?id=mktg.mc_cab_link_data_extensions.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 12d566d49800889af34b981868d9d8ed1ff44b906e65b8c0f3063a095131c220
description: Link data extensions within Data Designer for Contact Builder.
products:
  - Marketing
  - Marketing Cloud Engagement
release: "264"
---
# Link Data Extensions in Contact Builder

Link data extensions within Data Designer for Contact Builder.

- You can’t link an attribute with a field name longer than 256 characters.

- You can’t link a data extension with the "All records and data extensions" retention policy to the Contact model.

- Your existing data extensions remain linked to the Contact model unless you unlink them. You can't relink after they’re unlinked.

- You can’t delete a data extension that’s linked to the Contact model in Contact Builder or by using APIs.

- The word Contact is a reserved word. As a result, you can't link a data extension called Contact to an attribute group in Data Designer.

- Data Designer doesn’t support linking data extensions with non-English language characters in the name.

1. Click the attribute group in the constellation view.
2. Review the warning regarding the effects of changes on your data model and click **OK**.
3. To link a data extension within the attribute group for the first time, follow these steps:
    1. Click the arrow next to Data Extensions and select **Link**.
    2. Select the data extension.
4. To link an already-linked data extension to another data extension within the attribute group, follow these steps:
    1. Click the add link icon next to the data extension.
    2. Select the data extension in the second column of the **Link Data Extension** window.
5. Click next to each data extension name and choose the cardinality for your data relationship. Cardinality options are One-to-One, One-to-Many, Many-to-One, and Many-to-Many.
6. Select the data extension attribute in the first column of the **Link Data Extension** window.
7. Select the data extension attribute in the second column of the **Link Data Extension** window. You can link attributes with different names as long as the data types match. For example, match an email address to an email address or a mobile number to a mobile number.
8. Repeat these steps for other attributes to link between those two data extensions.
9. To redo any changes you perform during this procedure, click **Link** under the name of the data extension in the second column.
10. When you complete the linking process, click **Save.**