External lookups

We can create two special lookups on the external object along with the standard lookup relationship.

An external lookup creates a relationship that links an external object to another external object whose data is stored in an external data source.

An indirect lookup relationship creates a relationship that links an external object to a standard or custom object. We can only create an indirect lookup to an object that has a unique, external ID field on the parent object that is used to match the records in this relationship. For example, we can display a related list of sales orders from the SAP external record with matching external IDs on the Account record.