What is window function usage in transformation?

< 1 min read

Window functions perform calculations across a set of rows related to the current row.
In my project, we used ROW_NUMBER() to rank customers by total sales within each region.
RANK() helped identify top-selling products per category.
SUM() OVER(PARTITION BY Region) calculated cumulative sales by region.
LEAD() and LAG() were used to find previous or next order amounts.
They don’t collapse rows like GROUP BY, so full detail is preserved.
Applied in SQL before extraction to reduce Power Query processing.
Helps create analytics-ready metrics like running totals, ranks, and moving averages.
Improves performance and ensures consistent calculations across dashboards.
So window functions enhance data for advanced reporting and insights.

Power BI Essentials