Splits the data into groups so that ranking or row navigation starts again in each one. This DAX helper is only valid within window functions.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains PARTITIONBY in context, with comparison tables and the common traps.
Terms in this definition
- DAX
Short for Data Analysis Expressions, the formula language you write measures, calculated columns and row-level security rules in, within tabular semantic models in Power BI, Excel Power Pivot or Analysis Services.
- Window functions
Calculate across rows related to whichever row is current, e.g. rankings or running totals. DAX provides OFFSET, WINDOW, INDEX, RANK and ROWNUMBER, partitioned and ordered through PARTITIONBY and ORDERBY; T-SQL uses OVER, applied once GROUP BY and HAVING finish.
Related terms
- RANK
A window function, found in T-SQL (used with OVER) and in DAX, that gives each row's position within its partition. In DAX it accepts ORDERBY and PARTITIONBY, skips ranks after ties unless DENSE is chosen, and returns blank for total rows.