Data Warehouse Modeling Flashcards

In a star schema, what is the central table that contains measurable business metrics called?

Answer: Fact table

The fact table sits at the center of a star schema and holds quantitative measures plus foreign keys to dimensions.

A snowflake schema differs from a star schema primarily because its dimension tables are:

Answer: Normalized into multiple related tables

Snowflake schemas normalize dimensions into multiple related tables, reducing redundancy at the cost of more joins.

Which type of fact table stores a row only when an event occurs, such as a single sale?

Answer: Transaction fact table

A transaction fact table records one row per discrete business event as it happens.

What is the grain of a fact table?

Answer: The level of detail represented by one row

Grain defines exactly what a single fact row represents, such as one line item per order.

A factless fact table is most commonly used to:

Answer: Record events or coverage with no numeric measures

Factless fact tables capture the occurrence of events or relationships without storing numeric measures.

Which key type uniquely identifies a row in a dimension table within the warehouse, independent of the source system?

Answer: Surrogate key

A surrogate key is a warehouse-generated integer that uniquely identifies dimension rows regardless of source identifiers.

Conformed dimensions are valuable in a data warehouse because they:

Answer: Are shared consistently across multiple fact tables or data marts

Conformed dimensions have consistent meaning and content across fact tables, enabling cross-process analysis.