Hi,
it has nothing to do with diagrams.
It's about data_modeling. Ideally, your table_associations should look like a star, with one fact_table and a number of dimension_tables around it (which just add more info on some of the fields in the fact_table).
Snowflake_schema is the next best when that cannot be done, e.g. when you have several fact_tables.
In practice, though, that is not so terribly important - when your app works and delivers the figures you need, you're all right.
