The correct answer is that the transformation will result in errors for rows containing commas. This happens because Power Query’s default type conversion for numeric columns expects a period as the decimal separator and no thousands separator at all; when the SalesAmount column contains values like '1,234.56', the comma is not recognized as a valid numeric character in the default locale, so Power Query fails to parse it and throws an error for each affected row. On the Microsoft Power BI Data Analyst PL-300 exam, this scenario tests your understanding of locale-sensitive data import and the pitfalls of direct type changes without first cleaning separators—a common trap where candidates assume Power Query automatically handles regional formatting. To avoid this, always use the Replace Values step to remove commas before converting to a number type. Remember the memory tip: commas in numbers are for display, not for calculation—strip them first.
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.
```
Table.TransformColumnTypes(Source,{{"SalesAmount", type number},
{"OrderDate", type datetime},
{"CustomerID", type text}})
```
You are reviewing a Power Query M expression that transforms column types. The 'SalesAmount' column contains values like '1,234.56' (with a comma as thousands separator). After applying this transformation, what is the likely result?
Refer to the exhibit.
```
Table.TransformColumnTypes(Source,{{"SalesAmount", type number},
{"OrderDate", type datetime},
{"CustomerID", type text}})
```
A
The transformation will result in errors for rows containing commas.
The comma causes the conversion to fail, resulting in errors.
B
The column will be converted to text automatically.
Why wrong: The transformation attempts to convert to number; if it fails, the column will still be text but with errors.
C
The column will be successfully converted to numbers.
Why wrong: It may fail because the comma is not a valid decimal separator in the default locale.
D
The transformation will ignore the comma and convert the number correctly.
Why wrong: Power Query is strict; it does not ignore invalid characters.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The transformation will result in errors for rows containing commas.
Option A is correct because Power Query's default type conversion for numeric columns expects a period as the decimal separator and no thousands separator. When the 'SalesAmount' column contains values like '1,234.56' with a comma as a thousands separator, attempting to convert the column directly to a number type (e.g., using 'Change Type' or 'Table.TransformColumnTypes') will cause errors for rows containing commas, as Power Query cannot parse the comma as part of a valid number. The comma is not a recognized numeric character in the default locale, so the conversion fails.
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 transformation will result in errors for rows containing commas.
Why this is correct
The comma causes the conversion to fail, resulting in errors.
Related concept
Read the scenario before looking for a memorised answer.
✗
The column will be converted to text automatically.
Why it's wrong here
The transformation attempts to convert to number; if it fails, the column will still be text but with errors.
✗
The column will be successfully converted to numbers.
Why it's wrong here
It may fail because the comma is not a valid decimal separator in the default locale.
✗
The transformation will ignore the comma and convert the number correctly.
Why it's wrong here
Power Query is strict; it does not ignore invalid characters.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume Power Query will automatically handle locale-specific formatting (like commas as thousands separators) during type conversion, but in reality, it fails with errors unless the data is preprocessed or the correct culture is specified.
Detailed technical explanation
How to think about this question
Under the hood, Power Query uses the .NET 'Number' type conversion, which relies on the invariant culture by default, where the thousands separator is not a comma. To handle such data, you must first use 'Replace Values' to remove commas or use 'Table.TransformColumnTypes' with a specific culture parameter (e.g., 'en-US' where comma is a thousands separator). In real-world scenarios, this is a common issue when importing CSV files from European locales where comma is a decimal separator, leading to silent errors if not addressed.
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: The transformation will result in errors for rows containing commas. — Option A is correct because Power Query's default type conversion for numeric columns expects a period as the decimal separator and no thousands separator. When the 'SalesAmount' column contains values like '1,234.56' with a comma as a thousands separator, attempting to convert the column directly to a number type (e.g., using 'Change Type' or 'Table.TransformColumnTypes') will cause errors for rows containing commas, as Power Query cannot parse the comma as part of a valid number. The comma is not a recognized numeric character in the default locale, so the conversion fails.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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