Basics
M Variables
Declaring M Variables
M variables use let to define reusable data steps.
Introduction to M Variables
M variables are a powerful feature of the M language used in Power Query to define and store expressions for reuse. By using the let keyword, you can create variables that make your data transformation scripts more readable and efficient.
Defining M Variables
To define a variable in M, use the let expression. This expression allows you to bind names to values or expressions, which can then be used in subsequent steps. The typical structure of a let expression is as follows:
Example of Using M Variables
Consider a scenario where you want to perform a series of transformations on a dataset. Using M variables, you can break down these transformations into manageable steps. Here's an example:
In this example:
Source: Loads the data from an Excel table named "SalesData".FilteredRows: Filters the rows where sales are greater than 1000.SortedTable: Sorts the filtered data in descending order based on the "Sales" column.FinalResult: Selects only the "Product" and "Sales" columns for the final output.
Benefits of Using M Variables
Using variables in M has several benefits:
- Readability: Variables make your code easier to read by breaking down complex expressions into descriptive steps.
- Reusability: Once defined, variables can be reused in multiple expressions, reducing redundancy.
- Maintainability: With variables, updating or changing a part of the logic becomes straightforward as you only need to modify the specific part of the code.
Best Practices for M Variables
Here are some best practices when working with M variables:
- Use meaningful names for variables that clearly describe their purpose.
- Keep the variable scope as narrow as possible to avoid unwanted side-effects.
- Document complex logic within your code using comments.
Basics
- Previous
- Syntax
- Next
- Data Types
