Define a Function with Optional Parameters in Power Query M

Notes

Optional parameters that are omitted come through as null, so check for null rather than assuming a default value.

Requirements

• None - this is a standalone function example; paste it into your own query.

How to use this snippet

1. 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).
2. Paste the snippet and replace the placeholder names (tables, columns, file paths) with your own. Check the requirements above first.
3. Run it through the Power Query M Formatter to tidy the layout.

Related Power Query M snippets

• Create a Reusable Custom FunctionDefines a query as a function so it can be called with different arguments from other queries.
• Write a Recursive Function with @Defines a function that calls itself using the @ self-reference operator, useful for recursive calculations like factorials.
• Build a Function That Returns Another FunctionCreates a function that, given one argument, returns a new specialized function - a pattern known as currying.

More Power Query M resources

Browse all 145 snippets in the Power Query M Code Snippets, or search the library for something similar to Define a Function with Optional Parameters.