The correct answer is to apply a date filter in Power Query on the source query so only current year data is imported. This technique works because Power Query performs query folding, pushing the filter down to Azure SQL Database as a WHERE clause in the native SQL query, meaning only the filtered rows—rather than the entire 100-million-row table—are transferred over the network and loaded into the Power BI data model. On the PL-300 exam, this scenario tests your understanding of query folding and source-level filtering as the most efficient data reduction strategy for large databases; a common trap is to load all data and filter later in the report, which wastes memory and refresh time. Remember the key principle: always filter as early as possible in the data retrieval process, ideally at the source query level. A useful memory tip is "fold it early, load it lightly"—if Power Query can fold the filter, the database does the heavy lifting.
PL-300 Prepare the data Practice Question
This PL-300 practice question tests your understanding of prepare the data. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 connect to a large Azure SQL Database table with over 100 million rows. You need to create a report that shows sales by month for the current year only. Which data reduction technique should you use in Power Query to minimize data load?
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
✓
In Power Query, apply a date filter on the source query so only current year data is imported.
Option B is correct because applying a date filter in Power Query at the source query level ensures that only rows from the current year are imported into the Power BI data model. This reduces the data volume from over 100 million rows to a fraction, minimizing memory usage and improving refresh performance. Power Query pushes the filter down to the Azure SQL Database using a WHERE clause in the SQL query, so only the filtered data is transferred over the network.
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 all data and then remove columns that are not needed.
Why it's wrong here
Still loads all rows.
✓
In Power Query, apply a date filter on the source query so only current year data is imported.
Why this is correct
Query Folding pushes the filter to the 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.
✗
Load all data and filter using a visual-level filter in the report.
Why it's wrong here
This loads unnecessary data, causing slow performance.
✗
Use a calculated table in DAX to filter the data.
Why it's wrong here
Calculated tables are built after data load, so they don't reduce load.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume visual-level filters or DAX calculated tables are sufficient for performance, but they fail to realize that data reduction must occur at the data source or during import to minimize memory and refresh time.
Detailed technical explanation
How to think about this question
Power Query's query folding capability translates the date filter into a SQL WHERE clause (e.g., WHERE YEAR(OrderDate) = YEAR(GETDATE())), which is executed on the Azure SQL Database server. This reduces network transfer and leverages database indexing for faster filtering. In contrast, without query folding, Power Query would pull all rows and filter locally, which is inefficient for large tables.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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: In Power Query, apply a date filter on the source query so only current year data is imported. — Option B is correct because applying a date filter in Power Query at the source query level ensures that only rows from the current year are imported into the Power BI data model. This reduces the data volume from over 100 million rows to a fraction, minimizing memory usage and improving refresh performance. Power Query pushes the filter down to the Azure SQL Database using a WHERE clause in the SQL query, so only the filtered data is transferred over the network.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You are connecting to an Azure SQL Database from Power BI Desktop. The database contains a view that returns thousands of rows. You only need the last 100 rows for analysis. What is the most efficient way to reduce the data loaded?
easy
A.Write a native SQL query with a WHERE clause to limit rows
B.Use DirectQuery mode and add a filter in the report
C.Import all rows and then remove rows in Power Query
✓ D.Use the 'Keep Top Rows' transformation in Power Query after applying a sort
Why D: Option B is correct because using the 'Top N' filter in Power Query pushes the filter to the source if supported, reducing data transfer. Option A is wrong because it loads all rows. Option C is wrong because DirectQuery does not reduce the load; it queries the source each time. Option D is wrong because native SQL query may still load all rows unless filtered.
Variation 2. You are connecting Power BI to an Azure SQL Database. The database contains a table 'Orders' with 10 million rows. You need to minimize the data load time and ensure that only the most recent 30 days of data are imported. Which approach should you use?
hard
A.Import the entire table and apply a date filter in Power Query Editor.
B.Enable incremental refresh policy with a filter on the date column.
C.Use DirectQuery mode and apply a date filter in the report.
✓ D.Use a Native Query that selects only the last 30 days of data.
Why D: Option D is correct because using a Native Query that selects only the last 30 days of data pushes the filtering logic to the Azure SQL Database, reducing the amount of data transferred over the network and imported into Power BI. This minimizes load time by avoiding the import of all 10 million rows, while still ensuring only the required 30-day window is brought into the data model.
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This PL-300 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PL-300 exam.
Question Discussion
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