One of the data sources being ingested into Dynamics 365 Customer Insights - Data is...

In Dynamics 365 Customer Insights - Data, primary key attributes must uniquely identify records and be consistent across the data source.

Whole Number and GUID are commonly used data types for primary keys because they can uniquely identify records and are natively supported for primary keys in databases.

String can also be used as a primary key if it uniquely identifies each record (e.g., an email address).

Integer and Boolean are generally not used as primary keys in Customer Insights because they may not provide unique identifiers suitable for all scenarios.