The answer is that Power Query detected text values in some rows of the column, so it set the entire column’s data type to text. This happens because Power Query’s column type detection logic scans every row during import; if even a single row contains a non-numeric entry, the engine defaults the whole column to text to prevent data loss or conversion errors. On the Microsoft Power BI Data Analyst PL-300 exam, this scenario tests your understanding of Power Query’s automatic type inference and its conservative approach to mixed data types—a common trap is assuming Power Query will split or convert the column automatically. Remember, Power Query prioritizes safety over assumption: one text value forces the entire column to text. A useful memory tip is “One bad apple texts the whole barrel”—if any row is non-numeric, the column stays as text.
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.
You are preparing data for a Power BI report. The source data contains a column with mixed data types: some values are numbers, others are text. When loading into Power Query, the entire column is typed as text. What is the likely cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Power Query detected that the column contains text values in some rows, so it set the data type to text
Power Query's column type detection logic examines the entire column during import. If any row contains a non-numeric value (e.g., text), Power Query defaults the entire column to text to avoid data loss or conversion errors. This is the standard behavior when mixed data types are present, regardless of the source format.
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 column was imported as text because the data source is a CSV file
Why it's wrong here
CSV files do not enforce types, but Power Query still tries to detect.
✓
Power Query detected that the column contains text values in some rows, so it set the data type to text
Why this is correct
Power Query automatically detects the data type based on the values in the column; mixed types default to text.
Related concept
Read the scenario before looking for a memorised answer.
✗
The 'Detect data type' option was disabled in Power Query settings
Why it's wrong here
Disabling detection would not cause a specific type; it would leave as any.
✗
The source data is stored as text in the database
Why it's wrong here
The question states mixed types, so the source likely has numbers and text.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the data source format (e.g., CSV) is the cause, but Power Query's type detection logic—not the source—is what forces the column to text when mixed data types are present.
Detailed technical explanation
How to think about this question
Under the hood, Power Query uses the M engine's type inference, which scans a sample of rows (up to 200 by default) to determine the most common data type. If any row in the sample contains text, the engine assigns the column as text to prevent errors during load. This behavior is controlled by the 'Type Detection' setting in Power Query options, but even with full detection, mixed types always result in text. In real-world scenarios, this often occurs when a column contains numeric IDs alongside descriptive codes like 'N/A' or 'Unknown'.
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: Power Query detected that the column contains text values in some rows, so it set the data type to text — Power Query's column type detection logic examines the entire column during import. If any row contains a non-numeric value (e.g., text), Power Query defaults the entire column to text to avoid data loss or conversion errors. This is the standard behavior when mixed data types are present, regardless of the source format.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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 with mixed data types (numbers and text). Power BI automatically assigns the data type as Text. You need to perform numerical aggregations on this column. What should you do?
easy
A.Split the column using a delimiter to separate numbers from text.
B.Create a relationship with a numeric table to enable aggregation.
C.Create a calculated column in DAX using VALUE() to convert the text to numbers.
✓ D.In Power Query Editor, change the data type of the column to Whole Number or Decimal Number.
Why D: Option A is correct because you need to change the data type to a numeric type in Power Query Editor to perform aggregations. Option B is wrong because splitting the column does not change the data type. Option C is wrong because creating a calculated column in DAX is less efficient and may still require type conversion. Option D is wrong because the relationship is not the issue.
Last reviewed: Jun 24, 2026
Question Discussion
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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.
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