Basics
M Errors
Handling M Errors
M errors use try-otherwise for robust data transformations.
Introduction to M Errors
In the world of data transformations, errors are inevitable. The M language, used in Power Query, provides robust mechanisms to handle these errors using the try and otherwise constructs. By leveraging these constructs, developers can ensure that their data transformations are both resilient and informative when encountering unexpected data types or values.
Using try-otherwise in M
The try expression in M allows you to attempt a computation that might fail, while the otherwise clause provides a fallback value or operation if the attempt fails. This is particularly useful in scenarios where data might be incomplete or corrupted.
In the code example above, we attempt to convert each element of the list {1, 2, "three", 4} to a number. When the conversion fails (as it does with the string "three"), the otherwise clause ensures that a default value of 0 is used instead.
Benefits of Using try-otherwise
The try-otherwise pattern offers several benefits:
- Error Handling: Allows graceful handling of errors without stopping the entire data transformation process.
- Data Integrity: Ensures that even if part of the data is faulty, the overall transformation can still proceed with default values.
- Debugging Aid: Provides insight into which elements failed during the transformation, aiding in debugging and improvement of data processes.
Common Use Cases
Some common use cases for try-otherwise in M include:
- Converting data types where the source data may not be consistent.
- Handling null or missing values by providing default replacements.
- Implementing conditional logic that requires fallbacks in case of errors.
