The correct choice is to import the raw data and perform transformations in Power Query. This minimizes load on the source database during Power BI refresh because expensive calculated columns defined in the SQL Server view are never executed on the source; instead, the raw data is extracted and all heavy lifting is offloaded to Power Query’s mashup engine. On the Microsoft Power BI Data Analyst PL-300 exam, this scenario tests your understanding of query folding and where to push compute work—a common trap is assuming that all logic should remain in SQL Server to reduce data volume, but the real goal is to reduce server-side processing cost. Remember that Power Query can apply transformations after extraction, so moving computation to the Power BI service or desktop environment protects the source database from expensive operations. A useful memory tip: “Pull raw, transform later—keep the source database a lighter.”
PL-300 Prepare the data Practice Question
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 importing data from a SQL Server view into Power BI. The view contains calculated columns that are expensive to compute. You want to minimize the load on the source database during refresh. What should you do?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Import the raw data and perform transformations in Power Query.
Option A is correct because importing raw data and performing transformations in Power Query offloads the computational burden from the SQL Server source to Power BI's mashup engine. This minimizes load on the source database during refresh, as expensive calculated columns are not executed on SQL Server. Power Query can apply transformations after the data is extracted, reducing the need for server-side 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.
✓
Import the raw data and perform transformations in Power Query.
Why this is correct
Transformations in Power Query are done in Power BI, reducing load on the source database.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable query folding to push transformations to SQL Server.
Why it's wrong here
Query folding pushes transformations to the source, increasing load.
✗
Use a native SQL query in Power Query to perform calculations.
Why it's wrong here
Native queries run on SQL Server, increasing load.
✗
Create a materialized view in SQL Server with the calculations.
Why it's wrong here
Materialized views store precomputed data but still require processing on SQL Server.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume pushing transformations to the source (via query folding or native SQL) is always more efficient, but the question specifically asks to minimize load on the source database, making offloading to Power Query the correct choice.
Detailed technical explanation
How to think about this question
Under the hood, Power Query's folding mechanism translates M expressions into SQL queries that are executed on the source database; disabling folding or importing raw data ensures that transformations are applied in Power BI's engine (the Mashup Container) using in-memory processing. In real-world scenarios, this approach is critical when dealing with large datasets or limited source database resources, as it allows Power BI to leverage its own compute capacity without impacting the operational database's performance. However, note that importing raw data may increase data transfer size and refresh time, so it's a trade-off between source load and network/storage overhead.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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: Import the raw data and perform transformations in Power Query. — Option A is correct because importing raw data and performing transformations in Power Query offloads the computational burden from the SQL Server source to Power BI's mashup engine. This minimizes load on the source database during refresh, as expensive calculated columns are not executed on SQL Server. Power Query can apply transformations after the data is extracted, reducing the need for server-side 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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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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