Data type changes in Power BI - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ dax_lod_result

intermediate

DAX Measure Output After Data Type Change

You have a column 'SalesAmount' stored as text. You create this DAX measure:

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

What will be the result when you use this measure in a report?

Power BI

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

A An error because SUM cannot aggregate text values

B The sum of all sales amounts converted automatically from text to number

C Zero, because text values are ignored in SUM aggregation

D The count of rows in the Sales table

💡 Hint

SUM requires numeric data types, text cannot be summed directly.

SUM function in DAX only works on numeric columns. If the column is text, it causes an error.

❓ visualization

intermediate

Effect of Changing Data Type on Visualization

You have a date column stored as text in Power BI. You change its data type to Date. What is the most likely effect on a line chart using this column on the axis?

A The line chart will correctly order points by date

B The line chart will fail to render due to incompatible data type

C The line chart will show points in alphabetical order of the date text

D The line chart will aggregate all points into one

💡 Hint

Dates as text sort alphabetically, dates as Date type sort chronologically.

Changing the column to Date type allows Power BI to order the axis chronologically, improving the line chart.

❓ data_modeling

advanced

Data Type Impact on Relationships

You have two tables: 'Orders' with 'OrderDate' as text, and 'Calendar' with 'Date' as Date type. You create a relationship between 'Orders[OrderDate]' and 'Calendar[Date]'. What will happen?

A Power BI will automatically convert text to Date and create the relationship

B The relationship will be created and work correctly

C The relationship will be created but cause incorrect filtering

D The relationship will not be created because data types do not match

💡 Hint

Relationships require matching data types on both sides.

Power BI requires both columns in a relationship to have the same data type. Text and Date types cannot be related directly.

🔧 Formula Fix

advanced

Fixing a Data Type Conversion Error in Power Query

You try to change a column 'Price' from text to decimal number in Power Query but get an error on some rows. What is the most likely cause?

A The column is already decimal number type

B Some rows contain non-numeric text like 'N/A' or empty strings

C Power Query does not support decimal numbers

D The data source is offline

💡 Hint

Non-numeric text cannot convert to numbers.

If text contains values that cannot be converted to numbers, Power Query throws an error during type change.

🧠 Conceptual

expert

Choosing Data Types for Performance and Accuracy

In a large sales dataset, which data type choice for the 'Quantity' column is best for balancing performance and accuracy?

A Date type to track quantity changes over time

B Decimal Number type to allow fractional quantities

C Whole Number type because quantities are always integers

D Text type to avoid conversion errors

💡 Hint

Think about the nature of quantity and data size impact.

Whole Number type uses less memory and is accurate for integer quantities, improving performance.