In Microsoft SQL Server, for example, a primary key usually equates to a clustered index. In SQLite, a primary key is usually just a unique index and is distinct from the special rowid column name.

If a single candidate key exists for a table, the single candidate key defaults into service as the primary key. When multiple choices exist, then one candidate key must be chosen as the primary key.

Now, this app uses surrogate keys extensively (Django doesn't allow composite primary keys and encourages the use of surrogates heavily). For the first migration scripts I've tentatively skipped ...

When working on a multidimensional design, every fact table within scope should be handled with care. In an ideal world, each low-level fact table represents the metrics related to a business event.