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 grainThe 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?

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

Fact table size

Need for aggregates

Aggregating fact table

Three way