PL-300 Prepare the data Practice Question
You are creating a Power BI report for a marketing team. The data is stored in a folder of CSV files on a network drive that is accessible from your computer. You need to combine all CSV files into a single table in Power BI. The files have the same structure. What should you do in Power Query?
⚠ Common exam trap
Many candidates confuse 'Append Queries' (which stacks rows) with 'Combine Files' (which automates the same process for a folder), or mistakenly think 'Merge Queries' (which joins columns) is appropriate for combining files with identical structures.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the 'Combine Files' transform after connecting to the folder.
Power Query's 'Combine Files' transform is specifically designed to handle multiple CSV files with identical schemas stored in a folder. When you connect to the folder as a data source, Power Query automatically generates a sample file query and a transformation function that applies the same steps to all files, then combines the results into a single table. This is the most efficient and recommended approach for this scenario, avoiding manual appending or merging.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Connect to each CSV file individually and use Append Queries.
Why it's wrong here
Connecting to each CSV file individually and then using Append Queries is functionally possible, but it is a manual, repetitive process that requires you to add every file separately and maintain that list whenever new files arrive. It also ignores the folder connector's built-in ability to discover and process all files at once, making it inefficient and error-prone compared to using the Combine Files transform.
- ✓
Use the 'Combine Files' transform after connecting to the folder.
Why this is correct
The 'Combine Files' transform is the correct approach because Power Query connects to the folder, reads a sample file to infer the schema, and then automatically applies the same transformation steps to every CSV in that folder, stacking them into a single table. It handles an arbitrary number of files, is refreshable when files are added or removed, and is the native, scalable pattern for importing multiple CSV files with identical structures.
- ✗
Use Merge Queries to join the files based on a common column.
Why it's wrong here
Merge Queries is the wrong tool here because it performs a relational join (e.g., inner, left outer) based on a common key column, which would horizontally combine columns from different tables and potentially duplicate rows, not stack the records from each CSV vertically. The goal is to append row sets from multiple files with the same columns, which is what Combine Files / Append Queries does, not a merge operation.
- ✗
Change the data source settings to treat the folder as a single data source.
Why it's wrong here
There is no data source setting that treats a folder as a single data source in the way the option implies; the folder connector simply returns a list of files as a query, but you still need to apply a transformation like Combine Files to actually load the contents of those files into one table. Changing data source settings only affects credentials, privacy levels, or gateway configuration, not how the folder's files are aggregated.
Go deeper
Related to this question
About these practice questions
One of 524 original PL-300 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.