First Power BI report - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ visualization

intermediate

Identify the best visual for showing sales trends over time

You have monthly sales data for the last year. Which Power BI visual should you use to clearly show the sales trend over time?

A Line Chart

B Pie Chart

C Stacked Bar Chart

D Card Visual

💡 Hint

Think about which visual best shows changes over time.

A Line Chart is best for showing trends over time because it connects data points in a continuous flow, making it easy to see increases or decreases month by month.

❓ dax_lod_result

intermediate

Calculate total sales for a specific product category

Given a sales table with columns: ProductCategory, SalesAmount, and Date, which DAX measure correctly calculates total sales for the 'Electronics' category?

Power BI

Total Electronics Sales = CALCULATE(SUM(Sales[SalesAmount]), Sales[ProductCategory] = "Electronics")

A Total Electronics Sales = SUMX(FILTER(Sales, Sales[ProductCategory] = "Electronics"), Sales[SalesAmount])

B Total Electronics Sales = CALCULATE(SUM(Sales[SalesAmount]), Sales[ProductCategory] = "Electronics")

C Total Electronics Sales = SUM(Sales[SalesAmount]) WHERE Sales[ProductCategory] = "Electronics"

D Total Electronics Sales = SUM(Sales[SalesAmount]) + Sales[ProductCategory] = "Electronics"

💡 Hint

Use CALCULATE to filter the data before summing.

Option B uses CALCULATE with a filter condition correctly. Option B is valid DAX but less efficient. Option B and D are invalid syntax.

❓ data_modeling

advanced

Choose the best relationship type for a star schema

You have a fact table with sales data and several dimension tables like Products and Customers. What is the best relationship type to connect the fact table to dimension tables in Power BI?

A One-to-one relationship with no filtering

B Many-to-many relationship with bidirectional filtering

C One-to-many relationship with single direction filtering from dimension to fact

D Many-to-one relationship with filtering from fact to dimension

💡 Hint

Think about how data flows in a star schema from dimensions to facts.

In a star schema, dimension tables filter the fact table. This is done with a one-to-many relationship from dimension (one) to fact (many) with single direction filtering.

🎯 Scenario

advanced

Improve report performance with large data

Your Power BI report is slow because it uses a large sales dataset. Which approach will best improve report performance?

A Use live connection to Excel files stored locally

B Import the entire dataset and use many calculated columns

C Create many visuals with complex filters on the report page

D Use DirectQuery mode and avoid calculated columns where possible

💡 Hint

Consider how data is accessed and calculations are done.

DirectQuery mode queries the data source directly, reducing memory use. Avoiding calculated columns reduces processing load. Importing large data or many complex visuals slows performance.

🔧 Formula Fix

expert

Identify the error in this DAX measure

What error will this DAX measure produce?

Total Sales Last Year = CALCULATE(SUM(Sales[SalesAmount]), SAMEPERIODLASTYEAR(Sales[Date]))

Power BI

Total Sales Last Year = CALCULATE(SUM(Sales[SalesAmount]), SAMEPERIODLASTYEAR(Sales[Date]))

A Error: SAMEPERIODLASTYEAR requires a continuous date column marked as Date table

B SyntaxError: Missing parentheses in SAMEPERIODLASTYEAR function

C No error, measure returns total sales for last year correctly

D TypeError: SUM function cannot be used inside CALCULATE

💡 Hint

Check the requirements for time intelligence functions in Power BI.

SAMEPERIODLASTYEAR requires the date column to be from a properly marked Date table with continuous dates. Without this, it produces an error. The syntax is correct, and SUM can be used inside CALCULATE.

Practice

1. What is the main purpose of creating a Power BI report?

easy

A. To create text documents for data

B. To write complex code for data processing

C. To store large amounts of raw data

D. To turn data into easy-to-understand visuals

Solution

1. Step 1: Understand Power BI report function

   Power BI reports are designed to visualize data, making it easier to understand.

2. Step 2: Compare options with report purpose

   Only turning data into visuals matches the report's main goal.

3. Final Answer:

   To turn data into easy-to-understand visuals -> Option D

4. Quick Check:

   Power BI reports = Visual data display [OK]

Hint: Reports = visuals, not coding or raw data [OK]

Common Mistakes:

• Thinking Power BI is for coding data processing
• Confusing reports with data storage
• Assuming reports create text documents

2. Which of the following is the correct way to add a field to a Power BI report visualization?

easy

A. Type the field name in a text box on the report

B. Drag the field from Fields pane to the report canvas

C. Write a SQL query to add the field

D. Upload the field as a separate file

Solution

1. Step 1: Recall how to add fields in Power BI

   Fields are added by dragging them from the Fields pane to the report canvas.

2. Step 2: Eliminate incorrect methods

   Writing SQL, typing names, or uploading files are not how fields are added to visuals.

3. Final Answer:

   Drag the field from Fields pane to the report canvas -> Option B

4. Quick Check:

   Drag fields to visuals = correct method [OK]

Hint: Drag fields from Fields pane to canvas [OK]

Common Mistakes:

• Trying to write SQL to add fields
• Typing field names manually
• Uploading fields as files

3. Given a dataset with sales data, what will happen if you drag the 'Sales Amount' field to the report canvas and select a Card visualization?

medium

A. It will show a blank report because Card needs a measure

B. It will list all sales transactions in a table

C. It will show the total sales amount as a single number

D. It will create a bar chart of sales by product

Solution

1. Step 1: Understand Card visualization purpose

   Card visuals display a single summarized number, like total sales.

2. Step 2: Analyze dragging 'Sales Amount' to Card

   Dragging a numeric field like 'Sales Amount' to Card shows its total sum.

3. Final Answer:

   It will show the total sales amount as a single number -> Option C

4. Quick Check:

   Card visual = single total number [OK]

Hint: Card shows one total number from numeric field [OK]

Common Mistakes:

• Expecting a table or chart from Card
• Thinking Card needs a special measure
• Confusing Card with bar chart

4. You created a report but the visual shows no data. Which of these is the most likely reason?

medium

A. You forgot to drag any fields into the visual

B. You used the wrong font color

C. You saved the report without a name

D. You closed Power BI Desktop

Solution

1. Step 1: Identify why visuals show no data

   Visuals need fields dragged into them to display data.

2. Step 2: Check other options for impact

   Font color or report name do not affect data display; closing Power BI stops work but is unrelated to visual data.

3. Final Answer:

   You forgot to drag any fields into the visual -> Option A

4. Quick Check:

   No fields dragged = no data shown [OK]

Hint: Visuals need fields dragged in to show data [OK]

Common Mistakes:

• Blaming font color for no data
• Thinking report name affects visuals
• Confusing closing app with visual data issue

5. You want to create a report that lets users filter sales by year and see total sales update instantly. Which two visuals should you use together?

hard

A. A slicer for Year and a Card for total sales

B. A table for Year and a pie chart for sales

C. A text box for Year and a bar chart for sales

D. A map for Year and a line chart for sales

Solution

1. Step 1: Identify filtering visual

   Slicers let users pick filter values like Year interactively.

2. Step 2: Identify visual showing total sales

   Card visual shows a single total number that updates with filters.

3. Step 3: Combine slicer and card for interactive filtering

   Using slicer for Year and Card for total sales lets users filter and see instant updates.

4. Final Answer:

   A slicer for Year and a Card for total sales -> Option A

5. Quick Check:

   Slicer + Card = interactive filter and total [OK]

Hint: Use slicer to filter and card to show total [OK]

Common Mistakes:

• Using text box instead of slicer for filtering
• Choosing visuals that don't update interactively
• Confusing map with year filter