The Star Schema

Concepts: dmStarSchema, dmSnowflakeSchema

Facts in the Center, Dimensions Around Them A star schema has one table in the middle (the fact table) surrounded by several tables around it (dimension tables). The fact table stores measurable events: a sale happened, a click occurred, a payment was processed. Dimension tables store the descriptive context: who (customer), what (product), when (date), where (store). The fact table is tall and narrow: billions of rows, each with a few FK columns pointing to dimensions plus a few numeric measure columns. Dimension tables are short and wide: thousands to millions of rows, each with many descriptive columns. The star shape emerges because every dimension connects to the central fact. Queries always start from the fact table and join outward to dimensions for filtering and grouping: 'total sa