Power BI Data Modelling: Star Schema vs Flat Tables Explained

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Power BI is a business intelligence tool that transforms raw data into reports and dashboards, and the quality of those outputs depends heavily on how data is structured beforehand. Data modelling involves organising information into logical tables connected by keys, rather than storing everything in a single large table. A flat table keeps all data in one grid, which is simple to use but leads to duplication and maintenance challenges, making it suitable only for small datasets. A star schema, by contrast, places a central fact table at the core surrounded by descriptive dimension tables, offering better performance, cleaner DAX measures, and easier filter management. The star schema is considered the preferred structure for Power BI semantic models and is well suited for use cases such as sales reporting, financial analysis, and customer analytics.

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