The answer is to check for the query folding indicators in the Power Query Editor. These indicators, typically shown as a table icon with a down arrow next to a step, confirm that the transformation is being translated into native SQL and executed directly on the SQL Server, rather than pulling all data into Power Query for processing. This is the core of query folding optimization: pushing transformations to the source reduces data transfer and dramatically improves performance. On the PL-300 exam, this concept tests your ability to identify performance bottlenecks in data loading; a common trap is assuming all steps fold automatically, especially after custom M code or certain operations like merging tables with non-SQL sources. A reliable memory tip is to think of the folded icon as a "green light" for server-side execution—if you see a grey or missing icon, that step is breaking folding and likely slowing your query. Always scan the step icons from top to bottom to pinpoint where folding stops, then reorder or rewrite those steps to maximize server-side processing.
PL-300 Prepare the data Practice Question
This PL-300 practice question tests your understanding of prepare the data. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 reviewing a Power Query query that loads data from a SQL Server database. The query includes multiple steps that perform data transformation. You want to ensure that the query is optimized by pushing as many transformations as possible to the SQL Server. What should you look for?
View the native SQL query generated by Power Query.
Why wrong: You can view the native query by right-clicking a step and selecting 'View Native Query', but this is not the primary way to check folding; however, it is a valid method. The question asks what you should look for, and the indicator is more direct. But option A is still correct.
B
Use the Performance Analyzer in Power BI Desktop.
Why wrong: Performance Analyzer measures query execution time, not folding.
C
Check for the 'Query Folding' indicators in the query editor.
Power Query shows icons (e.g., a folded paper) to indicate that a step is folded to the source.
D
Review the data preview for each step.
Why wrong: Data preview shows results, not whether transformations are pushed to source.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check for the 'Query Folding' indicators in the query editor.
Option C is correct because query folding indicators in Power Query Editor show whether transformations are being pushed to the SQL Server source. When a step shows a 'folded' icon (a table with a down arrow), it means the transformation is translated into native SQL and executed on the server, reducing data transfer and improving performance. Checking these indicators directly confirms which steps are folded and which are not, allowing you to optimize the query by reordering or rewriting steps to maximize folding.
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.
✗
View the native SQL query generated by Power Query.
Why it's wrong here
You can view the native query by right-clicking a step and selecting 'View Native Query', but this is not the primary way to check folding; however, it is a valid method. The question asks what you should look for, and the indicator is more direct. But option A is still correct.
✗
Use the Performance Analyzer in Power BI Desktop.
Why it's wrong here
Performance Analyzer measures query execution time, not folding.
✓
Check for the 'Query Folding' indicators in the query editor.
Why this is correct
Power Query shows icons (e.g., a folded paper) to indicate that a step is folded to the source.
Related concept
Read the scenario before looking for a memorised answer.
✗
Review the data preview for each step.
Why it's wrong here
Data preview shows results, not whether transformations are pushed to source.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse viewing the native SQL query (Option A) with checking query folding indicators, but the native query only shows the final aggregated SQL, not the folding status of each individual step, which is what the question specifically asks for.
Trap categories for this question
Command / output trap
Data preview shows results, not whether transformations are pushed to source.
Detailed technical explanation
How to think about this question
Query folding works by translating Power Query M expressions into SQL statements using the Value.NativeQuery or direct SQL generation via the OLE DB or ODBC provider. For SQL Server, Power Query can fold operations like filtering, grouping, and joins, but certain functions (e.g., custom columns with M code, date/time zone conversions) break folding and force local processing. In real-world scenarios, a step that appears simple, like adding a conditional column with an if-then-else, may not fold if it uses M functions that have no SQL equivalent, causing a significant performance hit on large datasets.
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: Check for the 'Query Folding' indicators in the query editor. — Option C is correct because query folding indicators in Power Query Editor show whether transformations are being pushed to the SQL Server source. When a step shows a 'folded' icon (a table with a down arrow), it means the transformation is translated into native SQL and executed on the server, reducing data transfer and improving performance. Checking these indicators directly confirms which steps are folded and which are not, allowing you to optimize the query by reordering or rewriting steps to maximize folding.
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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