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Data Warehouse Modeling Flashcards

7 cards from real Data Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. A Slowly Changing Dimension Type 2 handles attribute changes by:

    Answer: Adding a new row to preserve history

    SCD Type 2 inserts a new dimension row for each change, preserving full historical context.

  2. An SCD Type 1 approach manages a changed attribute by:

    Answer: Overwriting the existing value with no history

    SCD Type 1 simply overwrites the old value, keeping no record of prior states.

  3. Which columns are typically added to support an SCD Type 2 dimension?

    Answer: Effective date, expiration date, and a current flag

    SCD Type 2 uses effective/expiration dates and a current-record indicator to track row validity periods.

  4. An SCD Type 3 dimension tracks change by:

    Answer: Storing a limited 'previous value' column alongside the current value

    SCD Type 3 keeps a previous-value column, allowing comparison between current and one prior state.

  5. A rapidly changing attribute (like customer age band) is best handled by splitting it into a:

    Answer: Mini-dimension (junk or demographic dimension)

    Volatile attributes are moved into a mini-dimension to avoid exploding the main dimension's row count.

  6. What is a hybrid SCD Type 6 technique a combination of?

    Answer: Types 1, 2, and 3

    Type 6 (1+2+3) combines overwrite, new-row history, and previous-value columns for flexible reporting.

  7. Why is overwriting a natural key value risky in a dimension table?

    Answer: It can break historical fact-to-dimension relationships

    Surrogate keys insulate facts from natural-key changes, which otherwise could corrupt historical joins.