Demystifying Power BI Variables: A Comprehensive Guide to Understanding DAX and M Variables
summary
Walks through Power Query M showing let in as a record syntax, building a reusable column-rename function, buffering and adding an index to read “next row” sales, and using list.accumulate / list.generate for cross-row access; explains lazy evaluation so unused steps never run. Explains DAX variable scoping with VAR ... RETURN, shows variables hold table or scalar values but become constants when evaluated, highlights no native recursion in DAX, and warns about nonintuitive evaluation order and staging/performance tradeoffs.
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chapters (11)
- 0:00Power BI variables intro
- 1:13Power BI architecture
- 2:59Power Query variables
- 9:32Power Query demo
- 16:24Power Query advanced editor
- 25:32Power Query evaluation
- 31:38Semantic model & DAX vars
- 33:44DAX variable syntax
- 40:13DAX variable scoping
- 46:26DAX context limits
- 50:23Global DAX variables & Q&A
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