CSV and text file import in Power BI - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding CSV import delimiters

You import a CSV file into Power BI. The file uses semicolons (;) to separate values instead of commas (,). What must you do to correctly import the data?

A Rename the file extension from .csv to .txt before importing.

B Change the delimiter setting in the import options to semicolon.

C Open the file in Excel first and save it as a comma-separated CSV.

D No action needed; Power BI automatically detects semicolons.

💡 Hint

Think about how Power BI knows where one value ends and another begins.

Power BI needs to know the delimiter used in the file. If the file uses semicolons, you must specify this in the import settings to parse the data correctly.

❓ dax_lod_result

intermediate

Result of importing CSV with missing headers

You import a CSV file without headers into Power BI and choose the option 'Use first row as headers'. What will happen to the first row of data?

A The first row will be used as column headers and will not appear as data.

B The first row will be imported as data and also as headers, causing duplication.

C Power BI will generate default column names and keep the first row as data.

D The import will fail with an error about missing headers.

💡 Hint

Consider what the 'Use first row as headers' option does.

This option tells Power BI to treat the first row as column names, so it will not be included as data.

🔧 Formula Fix

advanced

Fixing import errors with text qualifiers

You import a CSV file where some fields contain commas inside quotes, like "New York, NY". After import, these fields are split incorrectly. Which option fixes this issue?

A Remove all commas from the CSV file before importing.

B Change the delimiter to a tab character.

C Set the text qualifier to double quotes (") in the import settings.

D Import the file as Excel instead of CSV.

💡 Hint

Think about how Power BI knows to treat commas inside quotes as part of the same field.

Text qualifiers tell Power BI to treat text inside quotes as a single field, even if it contains commas.

❓ visualization

advanced

Visualizing data quality after CSV import

You imported a CSV file with sales data. Some rows have missing values in the 'Sales Amount' column. Which visualization best helps identify how many rows have missing sales amounts?

A A pie chart showing total sales amount by product category.

B A scatter plot of sales amount versus quantity sold.

C A line chart showing sales amount over time.

D A bar chart showing count of rows grouped by whether 'Sales Amount' is blank or not.

💡 Hint

Focus on counting missing versus present values.

A bar chart grouped by blank or not blank values clearly shows how many rows have missing sales amounts.

🎯 Scenario

expert

Handling large CSV files with incremental refresh

Your company receives daily CSV files with millions of rows. You want to import these files into Power BI efficiently and update the data daily without reloading all historical data. What is the best approach?

A Use Power BI incremental refresh with a date column to load only new data each day.

B Manually append each daily CSV file to the existing dataset in Power BI Desktop.

C Import all CSV files into one large table every day, replacing the old data.

D Split the CSV files into smaller chunks and import each separately without refresh.

💡 Hint

Think about how to avoid reloading all data every day.

Incremental refresh allows Power BI to load only new or changed data based on a date column, improving performance with large datasets.

Practice

1. What is the primary purpose of importing CSV or text files into Power BI?

easy

A. To export Power BI reports to CSV format

B. To create visualizations without any data

C. To bring external data into Power BI for analysis

D. To write DAX formulas automatically

Solution

1. Step 1: Understand the role of CSV/text import

   CSV and text file import allows users to bring external data into Power BI.

2. Step 2: Identify the main use of imported data

   Imported data is used for analysis and creating reports in Power BI.

3. Final Answer:

   To bring external data into Power BI for analysis -> Option C

4. Quick Check:

   Importing data = Bringing external data in [OK]

Hint: Import means bringing data inside Power BI [OK]

Common Mistakes:

• Confusing import with export
• Thinking import creates visuals automatically
• Assuming import writes formulas

2. Which of the following is the correct way to start importing a CSV file in Power BI Desktop?

easy

A. Click 'Get Data' > 'CSV' and select the file

B. Write a DAX formula to load the CSV

C. Use the 'New Measure' button to import CSV

D. Drag and drop the CSV file into the report canvas

Solution

1. Step 1: Locate the import option in Power BI Desktop

   The correct method is to use the 'Get Data' button and choose 'CSV' to import files.

2. Step 2: Confirm the import process

   After selecting the CSV file, Power BI loads it into the data model or Power Query Editor.

3. Final Answer:

   Click 'Get Data' > 'CSV' and select the file -> Option A

4. Quick Check:

   Get Data > CSV = Correct import method [OK]

Hint: Use 'Get Data' menu to import files [OK]

Common Mistakes:

• Trying to import CSV via DAX formulas
• Using 'New Measure' which is for calculations
• Dragging files onto report canvas doesn't import

3. After importing a CSV file with columns 'Date', 'Sales', and 'Region', which Power Query step will correctly change the 'Date' column to date type?

medium

A. Table.AddColumn(Source, "Date", each DateTime.LocalNow())

B. Table.RenameColumns(Source, {{"Date", type date}})

C. Table.RemoveColumns(Source, {"Date"})

D. Table.TransformColumnTypes(Source, {{"Date", type date}})

Solution

1. Step 1: Identify the function to change column type

   Table.TransformColumnTypes changes the data type of specified columns.

2. Step 2: Confirm correct syntax for changing 'Date' column to date type

   The syntax Table.TransformColumnTypes(Source, {{"Date", type date}}) correctly changes 'Date' column type.

3. Final Answer:

   Table.TransformColumnTypes(Source, {{"Date", type date}}) -> Option D

4. Quick Check:

   TransformColumnTypes changes data type [OK]

Hint: Use TransformColumnTypes to set column data types [OK]

Common Mistakes:

• Using RenameColumns instead of TransformColumnTypes
• Removing the column instead of changing type
• Adding a new column instead of modifying existing

4. You imported a CSV file but the data preview shows all columns as 'Any' type and some dates are text. What is the best way to fix this in Power Query?

medium

A. Write a DAX measure to convert text to date

B. Manually change column types using 'Transform' > 'Data Type' menu

C. Delete the query and re-import the file

D. Ignore the issue and load data as is

Solution

1. Step 1: Identify how to fix incorrect data types in Power Query

   Power Query allows manual data type changes via the 'Transform' tab.

2. Step 2: Apply manual data type change to fix text dates

   Changing the column type to 'Date' converts text dates properly before loading.

3. Final Answer:

   Manually change column types using 'Transform' > 'Data Type' menu -> Option B

4. Quick Check:

   Manual type change fixes data type issues [OK]

Hint: Use Transform tab to fix column types before loading [OK]

Common Mistakes:

• Deleting query wastes work done
• Using DAX measure instead of fixing source data
• Ignoring data type issues causes errors later

5. You have multiple CSV files with the same structure in a folder. How can you efficiently import and combine them in Power BI?

hard

A. Use 'Get Data' > 'Folder', select the folder, then combine files in Power Query

B. Import each CSV file separately and merge tables manually in report view

C. Write a DAX formula to union all CSV files after import

D. Copy and paste CSV content into Power BI manually for each file

Solution

1. Step 1: Identify the best method to import multiple CSV files

   Power BI's 'Get Data' > 'Folder' option allows importing all files in a folder at once.

2. Step 2: Use Power Query's combine files feature

   After selecting the folder, Power Query can automatically combine files with the same structure.

3. Final Answer:

   Use 'Get Data' > 'Folder', select the folder, then combine files in Power Query -> Option A

4. Quick Check:

   Folder import + combine = efficient multi-file import [OK]

Hint: Use Folder import to combine many CSVs at once [OK]

Common Mistakes:

• Importing files one by one wastes time
• Trying to union files with DAX which is not for import
• Copy-pasting data is error-prone and slow