Business users want to compare data across years, but historical data structure has changed. What do you do?

< 1 min read

First, I would analyze how the historical data structure changed, such as column names, table schema, or calculation logic.
I would compare the old and new data models to understand which fields can still be aligned for year-over-year comparison.
If possible, I would create a mapping layer that standardizes the fields into a common structure.
For example, in one project product categories changed between years, so we created a mapping table to align old categories with the new ones.
Next, I would transform the historical data to match the current structure in the data preparation layer.
If exact alignment is not possible, I would clearly define assumptions or adjusted calculations.
I would validate the results with sample checks and discuss the approach with stakeholders to ensure the comparison is meaningful.
Finally, I would document the transformation logic so future reporting keeps the same comparison method.

Power BI Essentials