Write a Recursive Function with @ in Power Query M

Defines a function that calls itself using the @ self-reference operator, useful for recursive calculations like factorials.

Advanced M FunctionsAdvancedrecursionfunctionself-reference

Power Query M code

let
    Factorial = (n as number) as number =>
        if n <= 1 then 1 else n * @Factorial(n - 1)
in
    Factorial(5)

Notes

The @ before the function name marks a recursive self-reference - without it, M won't let a let-bound value refer back to itself.

Requirements

None - this is a standalone example; paste the inner logic into your own function.

How to use this snippet

In Power BI Desktop, choose Transform data to open Power Query, then open the Advanced Editor on a query (or start from a blank query).
Paste the snippet and replace the placeholder names (tables, columns, file paths) with your own. Check the requirements above first.
Run it through the Power Query M Formatter to tidy the layout.

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