Data step with related records

This is how to deploy data with related records. Bear in mind that all objects to be migrated must have an External Id field with unique values.

Account and contacts:

- Step 1 (Accounts): Select external_id__c, name, from account
- Step 2 (Contacts): Select external_id__c, firstname, lastname, account.external_id__c from contact
- Step 3 (Orders): Select external_id__c, date, account__r.external_id__c from order__c
- Step 4 (Order Line Items): Select external_id__c, order__r.external_id__c, quantity__c, price__c from order_line__c

How did we do?