Aggregates are precalculated summaries derived from fact tables at the lowest level of granularity, where facts are captured at the most detailed level possible from operational systems. Choosing a star schema with a fact table at the lowest grain has advantages, as it allows producing large result sets from a simple structure with dimension tables connected to a most granular fact table reflecting single orders, invoices, and products from operational systems. This requires aggregating the fact table to address the large size and need for aggregated views of the data.

2. Aggregates are precalculated summaries derived from
the most granular fact table(level of detail in the fact
table).
If the fact table is at the lowest grain
The facts or metrics are at the lowest possible level at
which they could be captured from the operational
system.
what is the Advantages of lowest grain?

3. Choose a simple STAR schema with the fact table at
the lowest possible level of granularity.
Assume four dimension table with most granular fact
table.
Operational system-single order, invoice, product and
so on.
Data warehouse- produce large result set(these
retrieve hundreds and thousands

7. Fact table size

9. Need for aggregates

11. Aggregating fact table

14. Three way