Before you start using a report or writing DAX expressions, you need to build the underlying data model. You can think of a data model like the chassis of a sports car. No matter how good the car looks, if it has a poorly designed chassis, it will give a poor driving experience. In the same way, no matter how good a report might look, if it's built using a poorly designed data model, then it won't be very easy to work with. Worse still, the report may contain inaccurate information.
In addition to making it easier to work with DAX expressions, a well-structured data model can also help to reduce the overall size of your Excel spreadsheet or Power BI Desktop file. Through careful planning, a well-designed data model can also improve performance.
The process of building a data model begins with importing data into tables and creating the relationships...