Star schema

A star schema is a way of arranging tables for reporting. In the middle sits one fact table: one row per event, such as an order line or a booking, with the amounts. Around it sit dimension tables: one row per customer, product or day, with the attributes you slice by. Each dimension is joined to the fact table on one key column, which is what makes the diagram look like a star.

The shape matters because a filter flows from a dimension to the facts. Choosing a customer country in a slicer narrows the order lines to that country, and every measure over the order lines follows.

Where it appears in DASH:Gen

When a Power BI report is built from several files, the largest one becomes the fact table and the others are joined to it where a key can be found; a calendar table is added as one more dimension when the data has a date. The model stage of the step-by-step route shows the result before any measure is written. How the joins are found is in several CSVs as one Power BI model. An HTML dashboard has no model: it works on one table, so files are best joined before the upload.

See also: Several CSVs as one Power BI model · DAX measure