The answer is a date format locale error in Power Query, where the system’s locale does not match the date pattern in the CSV. This occurs because the ‘Changed Type’ step in Power Query M code attempts to convert the ‘OrderDate’ column to a date type using the default locale settings; if the CSV uses a format like ‘dd/MM/yyyy’ but the locale expects ‘MM/dd/yyyy’, any value that doesn’t fit the expected pattern is converted to null. On the Microsoft Power BI Data Analyst PL-300 exam, this question tests your understanding of how locale-sensitive transformations can silently corrupt data, a common trap where candidates overlook the impact of regional settings on date parsing. The key is to remember that Power Query’s type detection relies on the file’s origin locale, not the data’s actual format. Memory tip: “Locale locks the date logic” — always check the regional format in the CSV header before applying a date type conversion.
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.
Exhibit
Refer to the exhibit.
let
Source = Csv.Document(File.Contents("C:\Data\Sales.csv"),[Delimiter=",", Columns=5, Encoding=1252, QuoteStyle=QuoteStyle.Csv]),
#"Promoted Headers" = Table.PromoteHeaders(Source, [PromoteAllScalars=true]),
#"Changed Type" = Table.TransformColumnTypes(#"Promoted Headers",{{"OrderDate", type date}, {"Amount", type number}}),
#"Replaced Value" = Table.ReplaceValue(#"Changed Type","null",null,Replacer.ReplaceValue,{"Product"}),
#"Filtered Rows" = Table.SelectRows(#"Replaced Value", each [Amount] > 0)
in
#"Filtered Rows"
Refer to the exhibit. The Power Query M code imports a CSV file. The import succeeds, but the 'OrderDate' column shows some dates as null even though they appear valid in the CSV. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The date format in the CSV is not recognized by the locale used in the transformation.
Option A is correct because the '#Changed Type' step converts the column to type date, which will fail for any value that is not a valid date, resulting in null. If the CSV contains dates in a non-standard format (e.g., 'MM/dd/yyyy' vs 'dd/MM/yyyy'), the conversion may produce null. Option B is wrong because promoted headers only affect the first row. Option C is wrong because replacing 'null' with null would not affect dates. Option D is wrong because filtering rows does not affect data types.
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 date format in the CSV is not recognized by the locale used in the transformation.
Why this is correct
Type conversion to date may fail if the date string does not match the locale's date format.
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 'Filtered Rows' step removes rows where Amount > 0, which may include valid dates.
Why it's wrong here
Filtering rows does not alter data values.
✗
The 'Promoted Headers' step incorrectly changes the data type of the OrderDate column.
Why it's wrong here
Promoting headers only sets the first row as column names, it does not change data types.
✗
The 'Replaced Value' step replaces 'null' with null, causing the date to become null.
Why it's wrong here
The replacement is on the 'Product' column, not OrderDate.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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 date format in the CSV is not recognized by the locale used in the transformation. — Option A is correct because the '#Changed Type' step converts the column to type date, which will fail for any value that is not a valid date, resulting in null. If the CSV contains dates in a non-standard format (e.g., 'MM/dd/yyyy' vs 'dd/MM/yyyy'), the conversion may produce null. Option B is wrong because promoted headers only affect the first row. Option C is wrong because replacing 'null' with null would not affect dates. Option D is wrong because filtering rows does not affect data types.
What should I do if I get this PL-300 question wrong?
Identify which PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
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 importing data from a CSV file that contains a column 'Date' with values in different formats (e.g., '01/15/2024', '2024-01-15'). You need to ensure all dates are recognized correctly. What should you do in Power Query?
easy
✓ A.In Power Query, set the data type to 'Date' and use 'Using Locale' to specify the correct locale for each file.
B.Change the data source to a SQL database.
C.Split the column into multiple columns and merge them back.
D.Use 'Replace Values' to standardize the date formats.
Why A: Option A is correct because Power Query's 'Using Locale' feature allows you to specify the cultural context (e.g., 'en-US' for MM/DD/YYYY or 'de-DE' for DD.MM.YYYY) when setting a column's data type to 'Date'. This ensures that dates in various formats, such as '01/15/2024' (US) and '2024-01-15' (ISO 8601), are interpreted correctly during import, as the locale dictates the expected date order and separator.
Variation 2. You are importing a CSV file into Power BI. The file contains a date column with values in the format 'MM/dd/yyyy'. However, Power Query interprets the dates as 'dd/MM/yyyy'. What should you do to correctly parse the dates?
easy
A.Change the system region settings of the Power BI service to US
✓ B.Use the 'Using Locale' option in the Change Type step to select the appropriate locale (e.g., English (United States))
C.Change the column data type to Text and then manually replace separators
D.Split the column into day, month, and year, then combine them in the correct order
Why B: Option B is correct because Power Query's 'Using Locale' option in the Change Type step allows you to specify the regional format of the source data (e.g., English (United States) for 'MM/dd/yyyy'). This overrides Power Query's default locale-based interpretation, ensuring dates are parsed correctly without altering the data or system settings.
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