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Core
Slowly Changing Dimensions (SCD)
Slowly changing dimensions are the patterns for handling dimension attributes that change over time, such as a customer moving cities or a product changing category. Type 1 overwrites history, Type 2 keeps versioned rows with effective dates and a current flag, and Type 3 keeps a prior-value column. Applied-AI interviews probe it because answering what something looked like at the time of an event requires deliberate history tracking, and most analysts only know how to overwrite.
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