Relationship between a fact table and a dimension table should always

The relationship between a fact table and a dimension table should be designed such that both tables are at the same level of granularity to ensure accurate and meaningful analysis. In a data model, the granularity of a table refers to the level of detail represented by each record.

When a fact table contains transactional data (like sales or interactions) and is joined with a dimension table (such as product or customer details), both should reflect the same level of granularity. For example, if the fact table records sales at the individual transaction level, the dimension table should also provide information that pertains to each transaction level, rather than aggregating or summarizing data at a different level, which could lead to inaccurate or misleading results in analytics.

Thus, having the same granularity helps ensure that the relationships between the two tables make sense and that the insights derived from the data are accurate and relevant. This alignment allows for effective dimension-based filtering, grouping, and aggregation during analysis. In contrast, variations in granularity can create discrepancies that complicate data interpretation and reporting.