Which schema normalizes dimensions into multiple related tables?

• A. Star schema
• B. Flat schema
• C. Unified schema
• D. Snowflake schema

Answer: (D)

Snowflake schema uses normalization of dimension data by splitting attributes into multiple related tables and linking them with keys. Instead of keeping all dimension attributes in a single wide table, the dimensions are broken into hierarchical pieces, such as Product, Product Subcategory, and Product Category, or Geography into Country, Region, and City. The fact table still references the leaf level of the dimension, but queries can access higher-level attributes by joining through the related dimension tables. This reduces data redundancy and ensures consistency across rows, since changes to a dimension attribute (like a category name) only need to be updated in one place. The trade-off is more complex queries with additional joins, which can impact performance, but the normalization helps maintain data integrity and supports more granular analysis when needed.