20+ practice questions focused on Prepare the data — one of the most tested topics on the Microsoft Power BI Data Analyst PL-300 exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Prepare the data PracticeWhen importing data from a CSV file, Power Query detects that the first row contains column headers. However, the actual data starts from row 2. The analyst notices that some rows have extra columns due to commas within quoted fields. What is the most efficient way to handle this issue?
Explanation: The 'Split Column by Delimiter' feature in Power Query, when configured to split at each occurrence of the comma delimiter, correctly handles commas that appear inside quoted fields. Power Query's M engine respects the standard CSV quoting rules (RFC 4180), so quoted commas are not treated as delimiters. This approach is the most efficient as it requires no manual cleanup and preserves data integrity.
A data analyst is preparing data from multiple Excel files stored in SharePoint. Each file has the same structure but different data. Which THREE steps are necessary to combine these files into a single table in Power Query?
Explanation: Connecting to the SharePoint folder allows Power Query to access all files in the folder as a single data source. This is the foundational step for the 'Combine Files' workflow, which then uses a sample file to infer the schema and automatically applies transformations to all matching files.
You are building a Power BI data model from a CSV file that contains sales transactions. The CSV file has a column named 'TransactionDate' that stores dates as text in the format 'YYYYMMDD'. You need to create a date table that includes all dates from the transaction data. Which Power Query step should you use to convert the TransactionDate column to a date data type?
Explanation: The 'Parse' feature in Power Query, specifically the 'Parse -> Date' transformation, is designed to convert text columns with custom date formats like 'YYYYMMDD' into a proper date data type. This method intelligently interprets the text pattern without requiring locale-specific settings, making it the most direct and reliable approach for this format.
You are importing data from an Excel workbook that contains multiple worksheets. One worksheet has a column named 'Sales Amount' that contains values with different currencies (USD, EUR, JPY). You need to split the data into separate columns for each currency. Which Power Query transformation should you use?
Explanation: The correct transformation is Split Column by delimiter because the 'Sales Amount' column contains values with different currencies (USD, EUR, JPY) that are likely stored as text with a currency symbol or code prefix (e.g., '$100', '€200', '¥300'). Splitting by a delimiter (such as a space or the first character) allows you to separate the currency code from the numeric value into distinct columns, enabling further data type conversion and analysis per currency. This is a standard data cleansing technique in Power Query for parsing multi-currency data from a single column.
You are reviewing a Power Query query that combines data from multiple CSV files in a folder. The query uses the 'Combine Files' function. Which TWO actions can you take to improve the performance of this query?
Explanation: Disabling the 'Promote Headers' step reduces the number of transformations applied to each file during the combine operation. When headers are not needed, skipping this step avoids an extra row promotion and type detection pass, which can significantly reduce query execution time, especially when combining many files.
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Practice all Prepare the data questions1. Baseline your knowledge
Start with 10 questions to gauge your current understanding of Prepare the data. This tells you whether you need a concept refresher or just practice.
2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Prepare the data questions on the PL-300 frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Prepare the data is tested as part of the Microsoft Power BI Data Analyst PL-300 blueprint. Practicing with targeted Prepare the data questions ensures you can handle any format or difficulty that appears.
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