PL-300 Prepare the data Practice Question
You are importing data from a folder containing multiple CSV files with identical structure. You use the 'Combine files' transform in Power Query. Which TWO statements are true about this process?
⚠ Common exam trap
Candidates often confuse the 'sample file' as being the only file imported (Option B) or think the process uses an external tool like Power Automate (Option C), when in reality Power Query handles the entire merge natively with a generated function.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Power Query creates a function that applies the same transformations to each file.
Option D is correct because when you use the 'Combine files' transform in Power Query, it generates a reusable function (typically named 'Transform File' or similar) that encapsulates the transformations applied to the sample file, and then invokes that function for every other file in the folder so each file undergoes the same steps. Option E is correct because Power Query creates a separate sample file query (often named 'Sample File' or 'Transform Sample File') that acts as a template, defining the schema and transformation logic that the function applies to all files. Option A is not correct because the sample file is not automatically chosen by alphabetical order; Power Query typically selects the first file it encounters (often based on the folder's file listing order) and lets the user pick a different sample file if needed. Option B is not correct because all files in the folder are combined, not just the sample file. Option C is not correct because the combine process is handled entirely within Power Query's M engine, not by Power Automate.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The sample file is automatically selected as the first file in alphabetical order.
Why it's wrong here
This statement is incorrect because Power Query does not guarantee that the sample file is the first in alphabetical order. Instead, the sample file is chosen based on how the folder is enumerated by the file system, which often follows creation order, modification time, or an internal ordering that is not alphabetical. The sample file merely represents one instance of the file structure so Power Query can infer transformation steps; it is not a deliberate alphabetical selection.
- ✗
Only the sample file is imported; other files are ignored.
Why it's wrong here
This statement is false because the entire purpose of the Combine Files command in Power Query is to import and process every file in the folder, not just the sample. The sample file is used only as a template to define the transformation logic; after that, Power Query applies the same logic to each file and combines all resulting tables into one dataset. Ignoring the other files would defeat the merge operation entirely.
- ✗
The combine process uses Power Automate to merge files.
Why it's wrong here
This statement is wrong because the combine/merge process is executed entirely within Power Query's query engine, using native M-language functions such as Folder.Files and Table.Combine. Power Automate is a separate cloud orchestration service for automating workflows outside of Power Query; it is not invoked during a standard data import from a folder. No external automation service is required for this transformation.
- ✓
Power Query creates a function that applies the same transformations to each file.
Why this is correct
This statement correctly describes the core mechanism Power Query uses when combining files. After you provide a sample file, Power Query auto-generates a parameterized function (often named 'Transform File') that captures the transformation steps applied to the sample file. It then calls that function for each file in the folder, passing the file's path and contents as parameters, which ensures the same cleaning, filtering, or reshaping logic is applied consistently across all files.
- ✓
Power Query creates a sample file query that serves as a template for all files.
Why this is correct
This statement is also correct: Power Query creates a separate query for the sample file, which acts as a template documenting the exact transformations performed on that one file. This sample-file query is used by the auto-generated function as the basis for processing every other file, meaning any step you see in the sample query will be replicated across all files. In fact, the sample query is a prerequisite for the function to exist, and editing it updates the transformation logic for the entire combine process.
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