when to use flattened tables?

Hello,
Here's the definition by the admin:

The Flattened Table feature was designed based on a use case of small dimension tables. FT always puts the dimension table as the inner input to the join to make sure data integrity enforced.

How to create Flattened Tables:
vertica.com/docs/9.2.x/HTML/Content/Authoring/AnalyzingData/FlattenedTables/FlattenedTableCreate.htm essays.agency

In addition, as Flattened tables include columns that get their values by querying other tables,
Vertica executes the Flattened tables joins more efficiently and save the need to manually write and tune each Join.