Glossary
Surrogate Key
A surrogate key is a meaningless, system-generated identifier — an integer sequence or hash — used as the primary key of a dimension table in place of the source system’s own identifier (the natural key).
Surrogates exist because source keys can’t be trusted with history: they get recycled, change format, collide across systems, and can’t represent multiple versions of the same entity. A surrogate key decouples the warehouse from all of that — most importantly, it’s what allows a Type 2 slowly changing dimension to hold several rows for one customer, each version with its own key, so facts join to the version that was true when the fact happened.