Define the appropriate level of data granularity

One key way to establish what your report can contain is establishing its granularity, or grain. The grain is the smallest level your report can go to. It is not uncommon for data in a fact table to be stored as a daily or monthly total. If you are storing sales by store by day, you should not divide that number by 24 to get hourly totals. That number implies a degree of certainty that is not actually in the data.

I'm going to present a screenshot from earlier, but this time talk about what we are relating, not how.

Figure 5.17– The grain of the Sales table is product by Region Name and OrderNumber

Here, you can see that our Manager table can filter our Sales table through the Region table, and the other way around: Sales>Region>Manager. If I filter the Manager table by ManagerName, it will filter the Sales table by Region. So, if Ted and Ananya both manage the Midwest region, both will...