Contents
When do you declare the grain in dimensional modeling?
The grain establishes exactly what a single fact table row represents. The grain declaration becomes a binding contract on the design. The grain must be declared before choosing dimensions or facts because every candidate dimension or fact must be consistent with the grain.
When do you declare the grain in bi?
The grain must be declared before choosing dimensions or facts because every candidate dimension or fact must be consistent with the grain. This consistency enforces a uniformity on all dimensional designs that is critical to BI application performance and ease of use.
Why is it important to identify the grain in a fact table?
The grain conveys the level of detail that is associated with the fact table measurements. When you identify the grain, you also decide on the level of detail you want to make available in the dimensional model. If more detail is included, the level of granularity is lower.
How to identify the grain of a document?
The grain detail is based on the requirements findings that were analyzed and documented in Step 1: Identify business process requirements. Collect documents, such as invoices, receipts, and order memos. These documents often have information that you can use to define the grain.
Which is an example of declaring the grain?
Declaring the grain means saying exactly what a fact table record represents. Remember that a fact table record captures a measurement. Example declarations of the grain include: An individual line item on a customer’s retail sales ticket as measured by a scanner device An individual transaction against an insurance policy
How to declare the grain of the fact table?
In summary, try to do your dimensional designs using the following four steps, in order: 1. Decide on your sources of data. 2. Declare the grain of the fact table (preferably at the most atomic level). 3. Add dimensions for “everything you know” about this grain.