Facts are immutable: a line sold on 3 May stays sold. Dimension attributes drift: customers move, books change genre, prices are revised. A slowly changing dimension (SCD) technique decides what a report shows for yesterday's facts after an attribute changes today. This section covers the standard types, implements Type 2 on BookNest's star from Dimensional Modeling, and compares the three schools of warehouse design that frame those choices.
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Slowly Changing Dimensions
Slowly Changing Dimensions and Modeling Philosophies