Data type changes in Power BI - Dashboard Guide

Dashboard Mode - Data type changes

Business Question

How can changing data types improve data accuracy and reporting in sales analysis?

Sample Data

Order ID	Order Date	Customer	Sales Amount	Is Returned
1001	2024-01-15	Alice	250.00	FALSE
1002	2024-01-20	Bob	150.00	TRUE
1003	2024-02-05	Charlie	300.00	FALSE
1004	2024-02-10	Diana	200.00	FALSE
1005	2024-02-15	Eva	100.00	TRUE

Dashboard Components

• KPI Card: Total Sales
  Formula: Total Sales = SUM('Sales'[Sales Amount])
  Result: 1000.00
• KPI Card: Total Returned Orders
  Formula: Total Returned = COUNTROWS(FILTER('Sales', 'Sales'[Is Returned] = TRUE()))
  Result: 2
• Bar Chart: Sales by Month
  Data type change: 'Order Date' column changed to Date type to enable grouping by month.
  Formula: Use 'Order Date' month for axis, sum of 'Sales Amount' for values.
  Result: January = 400.00, February = 600.00
• Table: Orders with Correct Data Types
  Columns:
  • Order ID (Whole Number)
  • Order Date (Date)
  • Customer (Text)
  • Sales Amount (Decimal Number)
  • Is Returned (True/False)

Dashboard Layout

+----------------------+----------------------+
|    Total Sales KPI    | Total Returned Orders |
|        (1000)        |          (2)          |
+----------------------+----------------------+
|                      Bar Chart: Sales by Month                      |
|                    (Jan:400, Feb:600)                             |
+--------------------------------------------------------------------+
|                         Table: Orders Data                         |
+--------------------------------------------------------------------+

Interactivity

A slicer on Order Date allows filtering by month or date range. When a user selects a month, the bar chart updates to show sales for that month only. The KPI cards update to reflect total sales and returned orders within the selected date range. The table also filters to show only orders in the selected period.

Self Check

If you add a filter to show only orders where Is Returned = TRUE, which components update and how?

• Total Sales KPI: Updates to sum sales only for returned orders (250.00).
• Total Returned Orders KPI: Updates to count only returned orders (2).
• Bar Chart: Updates to show sales by month for returned orders only (January: 150.00, February: 100.00).
• Table: Shows only rows where orders were returned.

Key Result

Dashboard showing total sales, returned orders, monthly sales bar chart, and detailed orders table with correct data types.

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