You can manually define relationships between fields across different collections in your Atlas entity-relationship diagram.
Note
Relationships are for annotation purposes only. Atlas does not store relationship information in your MongoDB database.
You can manually add relationships to your entity-relationship diagram by using one of the following methods:
Side Panel: Manually add a relationship by selecting a source collection.
Drag and Drop: Create a relationship by clicking and dragging from one collection to another.
In addition to specifying collection and field properties for each relationship, you can also specify cardinality. In data modeling, cardinality refers to the number of records in one collection that can relate to one or more records in another collection. Cardinality can help you decide whether to embed or reference data in your data model. To learn more, see Document Relationships.
Before You Add Relationships
To add relationships, ensure you have already generated a diagram.
Procedure
To learn how to add relationships to your entity-relationship diagram, select the tab corresponding to your preferred method:
Specify Relationship Properties.
Specify values for the following fields under Relationship Properties:
Local collection: The primary collection in the relationship.
Local field: The field in the primary collection.
Local cardinality: The number of unique values in the local field.
Foreign collection: The target collection in the relationship.
Foreign field: The field in the target collection.
Foreign cardinality: The number of unique values in the foreign field.
Atlas automatically saves and updates your changes as you make them.
Specify Relationship Properties.
Specify values for the following fields under Relationship Properties:
Local collection: The primary collection in the relationship.
Local field: The field in the primary collection.
Local cardinality: The number of unique values in the local field.
Foreign collection: The target collection in the relationship.
Foreign field: The field in the target collection.
Foreign cardinality: The number of unique values in the foreign field.
Atlas automatically saves and updates your changes as you make them.
After you create a relationship, Atlas displays each relationship in the Relationships tab.
A relationship is incomplete if either side is missing a collection or field. Atlas displays an incomplete relationship as an animated dashed line in the diagram. The collection node displays a warning that one or more relationships are unresolved. The Relationships tab also displays a icon next to the relationship. To resolve the warning, verify the linked collections and fields for the relationship.
Delete Relationships
To delete a relationship from your entity-relationship diagram: