33 real SCD & History questions from the Data Engineering bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is SCD Type 4?
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A.A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
B.A precomputed helper table in Data Vault that snapshots which satellite versions were active at given dates to simplify as-of querying.
C.A history technique splitting a dimension into a current-value mini table and a separate history table, keeping the main table small and fast.
D.A handling rule where the attribute never changes once set (retain original), such as a customer's original signup date.
2. Which term means: "A history technique splitting a dimension into a current-value mini table and a separate history table, keeping the main table small and fast."?
A.SCD Type 4 — The valid_from and valid_to columns on a Type 2 row that bound the period during which that version of the record was current.
B.SCD Type 4 — A boolean column (often is_current) marking the active version of a Type 2 dimension row so queries can filter to the latest state cheaply.
C.SCD Type 4 — A history technique splitting a dimension into a current-value mini table and a separate history table, keeping the main table small and fast.
D.SCD Type 4 — A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
A.A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting.
B.A boolean column (often is_current) marking the active version of a Type 2 dimension row so queries can filter to the latest state cheaply.
C.A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
D.A handling rule where the attribute never changes once set (retain original), such as a customer's original signup date.
5. Which term means: "A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting."?
A.SCD Type 6 — Issuing a new surrogate key for each Type 2 version of a business key so facts join to the dimension state that was current at event time.
B.SCD Type 6 — A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting.
C.SCD Type 6 — A separate dimension carved out of rapidly changing attributes (like age band or income band) to avoid exploding Type 2 history on the main dimension.
D.SCD Type 6 — A precomputed helper table in Data Vault that snapshots which satellite versions were active at given dates to simplify as-of querying.
A.A precomputed helper table in Data Vault that snapshots which satellite versions were active at given dates to simplify as-of querying.
B.A handling rule where the attribute never changes once set (retain original), such as a customer's original signup date.
C.A separate dimension carved out of rapidly changing attributes (like age band or income band) to avoid exploding Type 2 history on the main dimension.
D.A table the database itself versions over system or application time, automatically retaining history and supporting AS OF queries.
8. Which term means: "A separate dimension carved out of rapidly changing attributes (like age band or income band) to avoid exploding Type 2 history on the main dimension."?
A.mini-dimension — A boolean column (often is_current) marking the active version of a Type 2 dimension row so queries can filter to the latest state cheaply.
B.mini-dimension — Issuing a new surrogate key for each Type 2 version of a business key so facts join to the dimension state that was current at event time.
C.mini-dimension — A separate dimension carved out of rapidly changing attributes (like age band or income band) to avoid exploding Type 2 history on the main dimension.
D.mini-dimension — The valid_from and valid_to columns on a Type 2 row that bound the period during which that version of the record was current.
11. Which term means: "The valid_from and valid_to columns on a Type 2 row that bound the period during which that version of the record was current."?
A.effective date range — A hash of a row's tracked attributes compared between loads to detect changes efficiently, common in Data Vault satellites and SCD Type 2 loads.
B.effective date range — A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting.
C.effective date range — A precomputed helper table in Data Vault that snapshots which satellite versions were active at given dates to simplify as-of querying.
D.effective date range — The valid_from and valid_to columns on a Type 2 row that bound the period during which that version of the record was current.
A.A boolean column (often is_current) marking the active version of a Type 2 dimension row so queries can filter to the latest state cheaply.
B.A history technique splitting a dimension into a current-value mini table and a separate history table, keeping the main table small and fast.
C.The valid_from and valid_to columns on a Type 2 row that bound the period during which that version of the record was current.
D.A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting.
14. Which term means: "A boolean column (often is_current) marking the active version of a Type 2 dimension row so queries can filter to the latest state cheaply."?
A.current flag — A hash of a row's tracked attributes compared between loads to detect changes efficiently, common in Data Vault satellites and SCD Type 2 loads.
B.current flag — A history technique splitting a dimension into a current-value mini table and a separate history table, keeping the main table small and fast.
C.current flag — A boolean column (often is_current) marking the active version of a Type 2 dimension row so queries can filter to the latest state cheaply.
D.current flag — A precomputed helper table in Data Vault that snapshots which satellite versions were active at given dates to simplify as-of querying.
A.A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
B.The valid_from and valid_to columns on a Type 2 row that bound the period during which that version of the record was current.
C.A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting.
D.A table the database itself versions over system or application time, automatically retaining history and supporting AS OF queries.
17. Which term means: "A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member."?
A.late-arriving dimension — A separate dimension carved out of rapidly changing attributes (like age band or income band) to avoid exploding Type 2 history on the main dimension.
B.late-arriving dimension — A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
C.late-arriving dimension — A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting.
D.late-arriving dimension — A history technique splitting a dimension into a current-value mini table and a separate history table, keeping the main table small and fast.
20. Which term means: "A table the database itself versions over system or application time, automatically retaining history and supporting AS OF queries."?
A.temporal table — A hybrid combining Type 1, 2, and 3 (the name comes from 1+2+3) that keeps versioned rows plus current-value columns on each row for easy as-was and as-is reporting.
B.temporal table — A table the database itself versions over system or application time, automatically retaining history and supporting AS OF queries.
C.temporal table — A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
D.temporal table — A boolean column (often is_current) marking the active version of a Type 2 dimension row so queries can filter to the latest state cheaply.
A.A separate dimension carved out of rapidly changing attributes (like age band or income band) to avoid exploding Type 2 history on the main dimension.
B.A history technique splitting a dimension into a current-value mini table and a separate history table, keeping the main table small and fast.
C.A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
D.A handling rule where the attribute never changes once set (retain original), such as a customer's original signup date.
A.SCD Type 0 — A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
B.SCD Type 0 — A table the database itself versions over system or application time, automatically retaining history and supporting AS OF queries.
C.SCD Type 0 — Issuing a new surrogate key for each Type 2 version of a business key so facts join to the dimension state that was current at event time.
D.SCD Type 0 — A handling rule where the attribute never changes once set (retain original), such as a customer's original signup date.
26. Which term means: "A hash of a row's tracked attributes compared between loads to detect changes efficiently, common in Data Vault satellites and SCD Type 2 loads."?
A.hash diff — A fact row that arrives before its dimension record exists; handled by inserting a placeholder dimension row and updating it later, or assigning an inferred member.
B.hash diff — A precomputed helper table in Data Vault that snapshots which satellite versions were active at given dates to simplify as-of querying.
C.hash diff — A hash of a row's tracked attributes compared between loads to detect changes efficiently, common in Data Vault satellites and SCD Type 2 loads.
D.hash diff — The valid_from and valid_to columns on a Type 2 row that bound the period during which that version of the record was current.
29. Which term means: "Issuing a new surrogate key for each Type 2 version of a business key so facts join to the dimension state that was current at event time."?
A.versioning surrogate — A precomputed helper table in Data Vault that snapshots which satellite versions were active at given dates to simplify as-of querying.
B.versioning surrogate — A handling rule where the attribute never changes once set (retain original), such as a customer's original signup date.
C.versioning surrogate — Issuing a new surrogate key for each Type 2 version of a business key so facts join to the dimension state that was current at event time.
D.versioning surrogate — A table the database itself versions over system or application time, automatically retaining history and supporting AS OF queries.
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