Modeling dimension tables (star schema)

Dimensions are the descriptive tables (dim_country, dim_plan, dim_date) that fact tables join to for slicing. This skill builds them once, cleanly, so every other model reuses them instead of re-deriving lookups. Read modeling-warehouse-foundations first (joins + convertCurrency() live there). Catalog of common dimensions: references/dimension-catalog.md; recipes in references/posthog/ and references/dbt/.

Star schema in one screen

Facts (events, charges, revenue items) are long, keyed, and additive. Dimensions are short, one row per entity, descriptive. You model a dimension in three moves: