The correct answer is to use Replace Errors to replace error values with null. When Power Query attempts to convert an invalid date like '02/30/2023' to the Date type, it generates a row-level error because the date does not exist in the calendar. The Replace Errors transformation specifically targets these conversion errors and substitutes them with a null value, preserving the integrity of the rest of your dataset while clearly flagging problematic entries for later analysis. On the Microsoft Power BI Data Analyst PL-300 exam, this scenario tests your understanding of Power Query’s error-handling mechanisms versus data-cleaning alternatives like filtering rows or using conditional columns—a common trap is to try to fix the date string itself, but the exam expects you to recognize that invalid dates are structural errors that require error replacement. Remember the mnemonic: “When dates break, Replace Errors for the data’s sake.”
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.
You are importing data from a CSV file that contains a column 'OrderDate' with dates in the format 'MM/dd/yyyy'. Some rows have invalid dates like '02/30/2023'. What is the best way to handle these errors in Power Query?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use 'Replace Errors' to replace error values with null.
Option A is correct because 'Replace Errors' in Power Query allows you to replace error values (which occur when Power Query fails to convert an invalid date like '02/30/2023' to the Date type) with null. This preserves the rest of the data and keeps the query running without interruption, while clearly marking invalid entries for later handling or analysis.
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.
✓
Use 'Replace Errors' to replace error values with null.
Why this is correct
This keeps the row and sets the invalid date to null, which can be handled later in the model.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Remove rows with errors using 'Remove Rows' > 'Remove Errors'.
Why it's wrong here
This removes entire rows, which may discard other important data in those rows.
✗
Change the data type to 'Date' and ignore errors.
Why it's wrong here
Ignoring errors may cause the step to fail or produce unexpected results.
✗
Filter the column to exclude rows where the date is invalid after type conversion.
Why it's wrong here
This approach requires additional steps and may be less efficient than 'Replace errors'.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose 'Remove Errors' (Option B) thinking it cleans the data, but they overlook that it deletes entire rows, which may discard valid data in other columns — a common mistake in data preparation scenarios.
Detailed technical explanation
How to think about this question
Under the hood, Power Query evaluates each row when changing a column's data type; if a value cannot be coerced (e.g., '02/30/2023' is not a valid date), it produces an error at the cell level. The 'Replace Errors' transformation uses Table.ReplaceErrorValues, which replaces all error values in selected columns with a specified value (like null), allowing subsequent steps to handle missing data gracefully. In real-world ETL, this approach is preferred because it isolates invalid data without discarding potentially useful information from other columns.
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: Use 'Replace Errors' to replace error values with null. — Option A is correct because 'Replace Errors' in Power Query allows you to replace error values (which occur when Power Query fails to convert an invalid date like '02/30/2023' to the Date type) with null. This preserves the rest of the data and keeps the query running without interruption, while clearly marking invalid entries for later handling or analysis.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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