This PL-300 practice question tests your understanding of prepare the data. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are using Power Query Editor to combine multiple CSV files from a folder. Each file has the same structure except that some files have an extra column 'Region' that is not present in others. You need to merge all files into one table, ensuring that the 'Region' column appears for all rows, with nulls where missing. Which combine files option should you select?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use 'Combine & Transform' and then edit the function to include all columns.
Option C is correct because Power Query's 'Combine & Transform' generates a function that you can edit to explicitly include all columns from all files, even those that appear only in some files. By modifying the function to reference all columns (e.g., using `Table.ColumnNames` or a custom column list), the resulting merged table will contain the 'Region' column with null values for rows from files that lack it. This approach handles schema drift automatically without manual post-processing.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use 'Combine & Load' and then manually add the missing column.
Why it's wrong here
This would not automatically handle the extra column.
✗
Use 'Sample File' and then refresh.
Why it's wrong here
Sample File is not a combine option.
✓
Use 'Combine & Transform' and then edit the function to include all columns.
Why this is correct
This allows you to customize the combine logic to include all columns.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use 'Append Queries' after loading each file separately.
Why it's wrong here
This is inefficient and not the direct combine files feature.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume 'Combine & Transform' works like 'Combine & Load' and only merges files with identical schemas, missing the ability to edit the generated function to handle schema differences.
Detailed technical explanation
How to think about this question
Under the hood, Power Query's 'Combine & Transform' creates a parameterized function (e.g., `TransformFile`) that applies transformations to each file. By editing this function to use `Table.Combine` or `Table.ColumnNames` with a union of all columns, you can dynamically include columns that appear in any file. In real-world scenarios, this is critical when ingesting data from distributed sources where schema evolution (e.g., a new 'Region' column added to some files) is common, and you need a robust, refreshable solution.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Prepare the data — This question tests Prepare the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use 'Combine & Transform' and then edit the function to include all columns. — Option C is correct because Power Query's 'Combine & Transform' generates a function that you can edit to explicitly include all columns from all files, even those that appear only in some files. By modifying the function to reference all columns (e.g., using `Table.ColumnNames` or a custom column list), the resulting merged table will contain the 'Region' column with null values for rows from files that lack it. This approach handles schema drift automatically without manual post-processing.
What should I do if I get this PL-300 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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