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Data & Analytics · Intermediate

Grain

The level of detail one row of a fact table represents, such as one line item per order or one balance per account per day.

Definition

Declaring the grain is the most important step in dimensional design because it determines which dimensions and facts are valid. Atomic grain offers the most flexibility. Mixing grains in one table causes double counting.

Example

Grain: one row per product per store per day.

Exam tip

Budget data at month grain and sales at day grain belong in separate fact tables (or need a relationship at month level).

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