Surrogate Keys

Surrogate keys are system-generated identifiers that replace natural keys in dimensional models. Every dimension row gets its own surrogate key (customer_sk, product_sk, date_sk). Fact tables reference dimensions using these surrogate keys, not the natural business keys. Why Not Just Use Natural Keys? Natural keys (email, SKU, employee_id) come from source systems. They have three problems in analytical models: they change (email updates), they get reused (SKU recycled for a new product), and they complicate SCD Type 2 (a customer with 5 historical versions would have 5 rows with the same email, and fact rows need to reference the specific version). How Surrogate Keys Enable SCD Type 2 When a customer moves from Portland to Seattle, you create a new dimension row with a new surrogate key.