Data type changes in Power BI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a data type in Power BI?

A data type tells Power BI what kind of data is stored in a column, like numbers, text, or dates. It helps Power BI understand how to use the data.

beginner

Why do we need to change data types in Power BI?

Changing data types ensures data is used correctly. For example, numbers should be numbers to do math, and dates should be dates to sort or filter by time.

beginner

How can you change a column's data type in Power BI Desktop?

In Power BI Desktop, go to the Data view, select the column, then use the Data Type dropdown in the ribbon to pick the right type like Text, Whole Number, or Date/Time.

beginner

What happens if you try to do math on a text data type column?

Power BI will not calculate correctly because text is treated as words, not numbers. You must change the data type to a number to do math.

intermediate

Can changing data types affect your reports?

Yes, changing data types can fix errors or improve performance. But if done wrong, it can cause wrong results or break visuals.

Which data type should you use for a column with dates in Power BI?

A Boolean

B Text

C Whole Number

D Date/Time

Dates should use the Date/Time data type so Power BI can sort and filter by time correctly.

What is the first step to change a column's data type in Power BI Desktop?

A Open Power Query Editor

B Go to the Data view and select the column

C Create a new measure

D Refresh the data

You first select the column in Data view to change its data type using the ribbon options.

If a number column is mistakenly set as Text, what problem might occur?

A Math calculations will not work correctly

B Power BI will automatically fix it

C You can still do math without issues

D The column will disappear

Math calculations require numeric data types; text data types prevent correct math operations.

Which of these is NOT a common data type in Power BI?

A Whole Number

B Currency

C Image

D Boolean

Image is not a standard data type for columns in Power BI; common types include Whole Number, Currency, and Boolean.

What can happen if you change a data type incorrectly?

A Your report visuals might show wrong data

B Power BI will delete your data

C Nothing will change

D Power BI will automatically revert it

Incorrect data type changes can cause wrong results or break visuals in your reports.

Explain why changing data types is important in Power BI and give an example.

Think about what happens if you try to add text instead of numbers.

Describe the steps to change a column's data type in Power BI Desktop.

Focus on the interface steps in Power BI Desktop.

Practice

1. Why is it important to change data types correctly in Power BI?

easy

A. Because it speeds up the internet connection

B. Because it changes the color of the visuals automatically

C. Because it deletes duplicate rows in the dataset

D. Because it helps Power BI understand and process data accurately

Solution

1. Step 1: Understand the role of data types in Power BI

   Data types tell Power BI how to treat each column, like numbers or text.

2. Step 2: Recognize the impact of correct data types

   Correct types ensure calculations and visuals work properly without errors.

3. Final Answer:

   Because it helps Power BI understand and process data accurately -> Option D

4. Quick Check:

   Correct data types = Accurate processing [OK]

Hint: Data types guide Power BI how to handle data [OK]

Common Mistakes:

• Thinking data types change visual colors
• Believing data types remove duplicates
• Assuming data types affect internet speed

2. Which of the following is the correct way to change a column's data type to Whole Number in Power Query Editor?

easy

A. Right-click the column header, select 'Change Type' > 'Whole Number'

B. Double-click the column header and type 'Whole Number'

C. Click 'Home' tab and press 'Delete' key

D. Drag the column to the 'Values' area

Solution

1. Step 1: Recall how to change data types in Power Query Editor

   Right-clicking the column header opens a menu with 'Change Type' options.

2. Step 2: Identify the correct option for Whole Number

   Selecting 'Whole Number' under 'Change Type' sets the column data type correctly.

3. Final Answer:

   Right-click the column header, select 'Change Type' > 'Whole Number' -> Option A

4. Quick Check:

   Right-click > Change Type > Whole Number [OK]

Hint: Use right-click menu to change data types quickly [OK]

Common Mistakes:

• Trying to type data type directly in header
• Pressing Delete key removes data, not changes type
• Dragging columns changes layout, not data type

3. Given a column 'Sales' with text data type containing values like '100', '200', '300', what will be the result of this DAX measure after changing 'Sales' to Whole Number type?

Total Sales = SUM('Table'[Sales])

medium

A. It will return an error because SUM cannot be used on numbers

B. It will concatenate the text values: '100200300'

C. It will sum the numbers correctly: 600

D. It will return zero because the column is text

Solution

1. Step 1: Understand the effect of changing 'Sales' to Whole Number

   Changing 'Sales' from text to whole number converts values like '100' to 100 as numbers.

2. Step 2: Evaluate the SUM function on numeric data

   SUM adds numeric values, so 100 + 200 + 300 = 600.

3. Final Answer:

   It will sum the numbers correctly: 600 -> Option C

4. Quick Check:

   SUM of numbers = 600 [OK]

Hint: SUM works only on numeric data types [OK]

Common Mistakes:

• Expecting SUM to concatenate text
• Thinking SUM causes error on numbers
• Assuming text columns sum to zero

4. You changed a date column's data type to Text in Power Query, but your visuals show incorrect dates. What is the likely problem?

medium

A. Text data type improves date calculations automatically

B. Changing date to text breaks date calculations and sorting

C. Power BI ignores data types in visuals

D. You must refresh the data source to fix visuals

Solution

1. Step 1: Analyze the impact of changing date to text

   Changing a date column to text removes date properties, so calculations and sorting fail.

2. Step 2: Understand why visuals show incorrect dates

   Without date type, Power BI cannot interpret or order dates properly in visuals.

3. Final Answer:

   Changing date to text breaks date calculations and sorting -> Option B

4. Quick Check:

   Date as text breaks date logic [OK]

Hint: Keep date columns as Date type for correct visuals [OK]

Common Mistakes:

• Assuming text type improves date calculations
• Believing Power BI ignores data types in visuals
• Thinking refresh fixes data type issues

5. You have a column 'Price' imported as Text with values like '12.50', '15.00', and '9.99'. You want to calculate the total price in a measure. Which steps correctly fix the data type and calculate the total?

hard

A. Change 'Price' to Decimal Number in Power Query, then use Total Price = SUM('Table'[Price])

B. Keep 'Price' as Text and use Total Price = CONCATENATE('Table'[Price])

C. Change 'Price' to Whole Number and use Total Price = SUM('Table'[Price])

D. Change 'Price' to Date and use Total Price = SUM('Table'[Price])

Solution

1. Step 1: Identify correct data type for decimal prices

   Prices with decimals require Decimal Number type, not Whole Number or Text.

2. Step 2: Use SUM on Decimal Number column

   SUM works on numeric types, so after changing type, Total Price = SUM('Table'[Price]) calculates total correctly.

3. Final Answer:

   Change 'Price' to Decimal Number in Power Query, then use Total Price = SUM('Table'[Price]) -> Option A

4. Quick Check:

   Decimal type + SUM = correct total [OK]

Hint: Use Decimal Number for prices with decimals [OK]

Common Mistakes:

• Using Whole Number loses decimals
• Concatenating text instead of summing
• Changing price to Date type causes errors