Data is stored as facts and dimensions. What are fact and dimension tables?

In a dimensional data warehouse, data is organized into two main types of tables: fact tables and dimension tables. A fact table stores quantitative, measurable data about business events, such as sales revenue, units sold, or transaction amounts. These facts are typically numeric and can be aggregated. A dimension table contains descriptive attributes that provide context to the facts, such as product name, customer details, time periods, or geographic location. Dimension tables are usually denormalized and contain keys that link to the fact table. For example, a sales fact table might have columns for sales_amount, quantity, and foreign keys to product_id, customer_id, and date_id. The corresponding dimension tables would hold product_name, category, customer_name, and date components. This structure allows analysts to slice and dice the data by various dimensions, enabling efficient reporting and analysis.