The star schema organizes a data warehouse around a central fact table (measurable events, such as sales) linked to several dimension tables (date, product, customer). It simplifies analytical queries, which join the fact to its dimensions and then aggregate.
Example
SELECT d.annee, SUM(f.montant)
FROM faits_ventes f JOIN dim_date d ON d.id = f.date_id
GROUP BY d.annee;