Variables (VAR/RETURN) in Power BI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of using VAR in a DAX formula?

VAR lets you store a value or calculation temporarily inside a formula. It helps make formulas easier to read and faster to calculate by reusing the stored value.

beginner

How do you return the result of a variable in a DAX expression?

You use the RETURN keyword after defining variables with VAR. The expression after RETURN is the final output of the formula.

intermediate

Can you define multiple variables in a single DAX formula? How?

Yes, you can define multiple variables by writing several VAR statements one after another before the RETURN statement.

intermediate

Why is using variables in DAX formulas considered a best practice?

Variables improve readability, avoid repeating calculations, and can improve performance by calculating a value once and reusing it.

beginner

Write a simple DAX formula using VAR and RETURN to calculate the difference between total sales and total costs.

SalesMinusCosts = VAR TotalSales = SUM(Sales[Amount])
VAR TotalCosts = SUM(Costs[Amount])
RETURN TotalSales - TotalCosts

What keyword do you use to define a variable in a DAX formula?

A LET

B VAR

C DEFINE

D SET

VAR is the correct keyword to define variables in DAX.

What keyword follows variable definitions to specify the output in a DAX formula?

A RESULT

B OUTPUT

C END

D RETURN

RETURN specifies the final result after variables are defined.

Why might you use variables in a DAX formula?

A To store intermediate results for reuse

B To make formulas harder to read

C To avoid using RETURN

D To repeat calculations multiple times

Variables store intermediate results so you can reuse them, improving readability and performance.

Can you define more than one variable in a single DAX formula?

A No, only one variable per formula

B Yes, but only inside RETURN

C Yes, by writing multiple VAR statements before RETURN

D No, variables are not supported in DAX

You can define multiple variables by writing several VAR statements before the RETURN statement.

Which of these is a correct use of variables in DAX?

A VAR x = SUM(Sales[Amount]) RETURN x * 2

B LET x = SUM(Sales[Amount]) END x * 2

C DEFINE x = SUM(Sales[Amount]) RESULT x * 2

D SET x = SUM(Sales[Amount]) OUTPUT x * 2

Option A uses correct DAX syntax with VAR and RETURN.

Explain how to use VAR and RETURN in a DAX formula and why it is helpful.

Think about storing values and returning a final result.

Write a simple example of a DAX formula using two variables and returning their sum.

Use SUM or any simple calculation inside VAR.

Practice

1. What is the main purpose of using VAR in a DAX formula?

easy

A. To store a value temporarily for reuse within the formula

B. To create a new table in the data model

C. To filter rows in a table

D. To format the output of a measure

Solution

1. Step 1: Understand the role of VAR in DAX

   VAR is used to define a variable that holds a value temporarily inside a formula.

2. Step 2: Identify what VAR does in calculations

   It allows reuse of the stored value to simplify and speed up calculations.

3. Final Answer:

   To store a value temporarily for reuse within the formula -> Option A

4. Quick Check:

   VAR stores values temporarily [OK]

Hint: VAR holds values inside formulas for reuse [OK]

Common Mistakes:

• Thinking VAR creates tables
• Confusing VAR with filters
• Assuming VAR formats output

2. Which of the following is the correct syntax to define and return a variable in DAX?

easy

A. VAR Total = SUM(Sales[Amount]) RETURN Total

B. RETURN Total = SUM(Sales[Amount]) VAR Total

C. DEFINE VAR Total = SUM(Sales[Amount]) OUTPUT Total

D. LET Total = SUM(Sales[Amount]) THEN Total

Solution

1. Step 1: Recall correct DAX variable syntax

   In DAX, variables are defined with VAR and the result is returned with RETURN.

2. Step 2: Match syntax with options

   VAR Total = SUM(Sales[Amount]) RETURN Total uses VAR to define and RETURN to output, which is correct.

3. Final Answer:

   VAR Total = SUM(Sales[Amount]) RETURN Total -> Option A

4. Quick Check:

   VAR then RETURN is correct syntax [OK]

Hint: VAR first, then RETURN to output [OK]

Common Mistakes:

• Swapping VAR and RETURN order
• Using keywords like DEFINE or LET incorrectly
• Missing RETURN keyword

3. Consider the following DAX measure:

Measure = VAR SalesAmount = SUM(Sales[Amount]) VAR Tax = SalesAmount * 0.1 RETURN SalesAmount + Tax

What is the output of this measure if the total sales amount is 1000?

medium

A. 100

B. 1100

C. 900

D. 10

Solution

1. Step 1: Calculate SalesAmount variable

   SalesAmount = SUM(Sales[Amount]) = 1000.

2. Step 2: Calculate Tax variable

   Tax = SalesAmount * 0.1 = 1000 * 0.1 = 100.

3. Step 3: Calculate RETURN value

   Return SalesAmount + Tax = 1000 + 100 = 1100.

4. Final Answer:

   1100 -> Option B

5. Quick Check:

   1000 + 10% tax = 1100 [OK]

Hint: Calculate variables stepwise, then add in RETURN [OK]

Common Mistakes:

• Using only SalesAmount without tax
• Multiplying instead of adding tax
• Confusing tax rate calculation

4. Identify the error in this DAX measure:

Measure = VAR TotalSales = SUM(Sales[Amount]) RETURN TotalSales * 0.1 VAR Tax = TotalSales * 0.1

medium

A. Variable names cannot have uppercase letters

B. RETURN keyword is missing

C. Variables must be defined before RETURN statement

D. SUM function cannot be used inside VAR

Solution

1. Step 1: Review variable and RETURN order

   In DAX, all VAR definitions must come before the RETURN statement.

2. Step 2: Identify misplaced VAR

   The variable Tax is defined after RETURN, which is invalid syntax.

3. Final Answer:

   Variables must be defined before RETURN statement -> Option C

4. Quick Check:

   All VAR before RETURN [OK]

Hint: Define all VAR before RETURN [OK]

Common Mistakes:

• Placing VAR after RETURN
• Ignoring syntax order rules
• Assuming RETURN can appear multiple times

5. You want to create a measure that calculates the average sales per customer but only for customers with sales above 500. Which DAX measure using VAR and RETURN is correct?

hard

A. Measure = VAR FilteredSales = FILTER(Sales, Sales[Amount] < 500) VAR AvgSales = AVERAGEX(FilteredSales, Sales[Amount]) RETURN AvgSales

B. Measure = VAR AvgSales = AVERAGEX(Sales, Sales[Amount]) VAR FilteredSales = FILTER(Sales, Sales[Amount] > 500) RETURN AvgSales

C. Measure = RETURN VAR FilteredSales = FILTER(Sales, Sales[Amount] > 500) VAR AvgSales = AVERAGEX(FilteredSales, Sales[Amount])

D. Measure = VAR FilteredSales = FILTER(Sales, Sales[Amount] > 500) VAR AvgSales = AVERAGEX(FilteredSales, Sales[Amount]) RETURN AvgSales

Solution

1. Step 1: Filter sales above 500

   VAR FilteredSales uses FILTER to keep only sales > 500, which matches the requirement.

2. Step 2: Calculate average sales on filtered data

   VAR AvgSales uses AVERAGEX on FilteredSales to get average sales per customer.

3. Step 3: Return the calculated average

   RETURN outputs AvgSales, the correct final result.

4. Final Answer:

   Measure = VAR FilteredSales = FILTER(Sales, Sales[Amount] > 500) VAR AvgSales = AVERAGEX(FilteredSales, Sales[Amount]) RETURN AvgSales -> Option D

5. Quick Check:

   Filter then average, return result [OK]

Hint: Filter first, then calculate average, then RETURN [OK]

Common Mistakes:

• Defining variables after RETURN
• Filtering sales less than 500 instead of greater
• Returning variable before defining it