The correct answer is that the privacy levels for the SQL Server data source are set inconsistently across the environment. This triggers Power Query’s data privacy firewall, which blocks any operation—like merging or appending—when sources with incompatible privacy levels (e.g., Private vs. Public) are combined, even if you are only using a single source. On the Microsoft Power BI Data Analyst PL-300 exam, this scenario tests your understanding of how the firewall enforces isolation based on configured privacy levels, and a common trap is assuming the error only occurs with multiple sources. The key insight is that a single source can still fail if its privacy level is set inconsistently across different queries or environments. Memory tip: think of the firewall as a strict bouncer—if one copy of your ID says “VIP” and another says “Guest,” you’re not getting in, even if you’re the same person.
PL-300 Prepare the data Practice Question
This PL-300 practice question tests your understanding of prepare the data. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
let
Source = Sql.Database("server01", "AdventureWorks"),
dbo_SalesOrderHeader = Source{[Schema="dbo",Item="SalesOrderHeader"]}[Data],
#"Filtered Rows" = Table.SelectRows(dbo_SalesOrderHeader, each Date.Year([OrderDate]) = 2024),
#"Grouped Rows" = Table.Group(#"Filtered Rows", {"CustomerID"}, {{"TotalSales", each List.Sum([SubTotal]), type number}}),
#"Sorted Rows" = Table.Sort(#"Grouped Rows", {{["TotalSales"], Order.Descending}})
in
#"Sorted Rows"
Refer to the exhibit. The Power Query M code connects to a SQL Server database and performs data transformation. However, the query is failing with a privacy level error. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
let
Source = Sql.Database("server01", "AdventureWorks"),
dbo_SalesOrderHeader = Source{[Schema="dbo",Item="SalesOrderHeader"]}[Data],
#"Filtered Rows" = Table.SelectRows(dbo_SalesOrderHeader, each Date.Year([OrderDate]) = 2024),
#"Grouped Rows" = Table.Group(#"Filtered Rows", {"CustomerID"}, {{"TotalSales", each List.Sum([SubTotal]), type number}}),
#"Sorted Rows" = Table.Sort(#"Grouped Rows", {{["TotalSales"], Order.Descending}})
in
#"Sorted Rows"
A
The SQL Server credentials are not correctly configured in the data source settings.
Why wrong: Credential issues typically cause 'Cannot connect' errors, not privacy level errors.
B
The privacy levels for the SQL Server data source are set inconsistently across the environment.
Privacy level errors can occur even with a single source if the data source privacy setting is misconfigured or if the global privacy level is set to 'None' while the source is 'Private'.
C
The query uses a CSV file from a local folder that has a privacy level set to 'Private'.
Why wrong: No CSV file is referenced in the code.
D
The query combines data from SQL Server and another data source with incompatible privacy levels.
Why wrong: The query only uses one data source (SQL Server), so no combining occurs.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The privacy levels for the SQL Server data source are set inconsistently across the environment.
The privacy level error in Power Query occurs when data from sources with incompatible privacy levels is combined. Option B is correct because the most likely cause is that the SQL Server data source has its privacy level set inconsistently across the environment (e.g., one source set to 'Private' and another to 'Public'), which prevents the query from merging or appending data due to Power BI's data privacy firewall. This firewall enforces isolation between sources based on their configured privacy levels, and an inconsistency triggers the error.
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.
✗
The SQL Server credentials are not correctly configured in the data source settings.
Why it's wrong here
Credential issues typically cause 'Cannot connect' errors, not privacy level errors.
✓
The privacy levels for the SQL Server data source are set inconsistently across the environment.
Why this is correct
Privacy level errors can occur even with a single source if the data source privacy setting is misconfigured or if the global privacy level is set to 'None' while the source is 'Private'.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The query uses a CSV file from a local folder that has a privacy level set to 'Private'.
Why it's wrong here
No CSV file is referenced in the code.
✗
The query combines data from SQL Server and another data source with incompatible privacy levels.
Why it's wrong here
The query only uses one data source (SQL Server), so no combining occurs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a privacy level error always involves combining two different data sources (like SQL Server and a CSV), but the error can also occur when the same data source has inconsistent privacy level settings across the environment, such as between Power BI Desktop and the Power BI Service.
Detailed technical explanation
How to think about this question
Power Query's data privacy firewall uses the concept of 'privacy levels' (Private, Organizational, Public) to determine whether data can be combined across sources. When a query references a single source like SQL Server, the firewall still evaluates the privacy level of that source; if the same source is referenced in multiple queries or environments with different privacy levels (e.g., one report sets it to Private, another to Public), the firewall may block the query to prevent unintended data leakage. In real-world scenarios, this often happens when a Power BI Desktop file is published to the Power BI Service and the data source privacy settings in the service differ from those in Desktop, causing the refresh to fail with a privacy level error.
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: The privacy levels for the SQL Server data source are set inconsistently across the environment. — The privacy level error in Power Query occurs when data from sources with incompatible privacy levels is combined. Option B is correct because the most likely cause is that the SQL Server data source has its privacy level set inconsistently across the environment (e.g., one source set to 'Private' and another to 'Public'), which prevents the query from merging or appending data due to Power BI's data privacy firewall. This firewall enforces isolation between sources based on their configured privacy levels, and an inconsistency triggers the error.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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