What is the purpose of a fact table in a data warehouse?

• A. To store the raw data.
• B. To store metadata about the data warehouse.
• C. To store the results of calculations.
• D. To store data in a summarized form.

Answer: (C)

In a data warehouse, a fact table holds the numeric measurements that come from business processes—things you want to analyze like revenue, quantity sold, or hours worked—tied to the specific points in time or context through foreign keys to dimension tables (time, product, customer, etc.). Its main purpose is to store the results of calculations: the actual metrics you’ll report on and aggregate, such as price times quantity to get sales amount, or total cost and profit. This design supports fast, meaningful analytics when you group or roll up by different dimensions.

Raw transactional data live in source systems or a staging area, and metadata is kept in a separate catalog or metadata store. While some fact tables may hold data at a summarized grain, the essential role is to store the calculated measures that analysts use for reporting and analysis.