REVIEWED-PENDING DOCUMENTATION: Are JOIN statements allowed when creating a Dataset?

The question has repeatedly been asked by DQ customers, “Are JOIN statements allowed when creating an initial Dataset, in the scope query?” I have heard many different answers, so I asked Brian Mearns, the DQ Product Owner to clarify. He said : “When creating a DQ dataset, the DQ scope query will allow for a JOIN to be used. However, the best practice is not to use JOIN but rather to use a Materialized View. If a JOIN must be used this is a best effort, and most JOIN cases will work. Also for Outliers and Patterns that require ‘lookback’ periods, JOIN is not supported.”