Basic arithmetic in DAX in Power BI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is DAX?

DAX stands for Data Analysis Expressions. It is a formula language used in Power BI to create custom calculations and measures.

beginner

How do you add two columns in DAX?

You use the plus sign (+) to add two columns or values. For example: Total Sales = Sales[Price] + Sales[Tax].

beginner

Which symbol is used for multiplication in DAX?

The asterisk (*) is used for multiplication. For example: Total Cost = Sales[Quantity] * Sales[UnitPrice].

intermediate

What happens if you divide by zero in DAX?

Dividing by zero causes an error. To avoid this, use functions like DIVIDE() which safely handle division by zero.

beginner

Write a DAX formula to calculate the difference between two columns: Sales[Revenue] and Sales[Cost].

You can write: Profit = Sales[Revenue] - Sales[Cost]. This subtracts Cost from Revenue to get Profit.

Which symbol is used for subtraction in DAX?

A -

B /

C *

D +

The minus sign (-) is used for subtraction in DAX.

What does this DAX expression do? Total = Sales[Price] * Sales[Quantity]

A Adds Price and Quantity

B Multiplies Price by Quantity

C Divides Price by Quantity

D Subtracts Quantity from Price

The asterisk (*) multiplies Price by Quantity.

How can you safely divide two columns in DAX to avoid errors?

A Use the DIVIDE() function

B Use the + operator

C Use the / operator directly

D Use the * operator

DIVIDE() handles division by zero safely.

What is the result of 5 + 3 * 2 in DAX?

A 13

B 16

C 10

D 11

Multiplication has higher priority, so 3*2=6, then 5+6=11.

Which of these is NOT a basic arithmetic operator in DAX?

A +

B -

C %

D *

The percent sign (%) is not a basic arithmetic operator in DAX.

Explain how to perform basic arithmetic operations in DAX with examples.

Think about how you add or multiply numbers in math class.

Describe how to handle division by zero errors in DAX calculations.

Consider what happens if you try to divide by zero on a calculator.

Practice

1. What does the DAX expression Total Sales = SUMX(Sales, Sales[Quantity] * Sales[Price]) calculate?

easy

A. The division of quantity by price

B. The sum of quantity and price

C. The difference between quantity and price

D. The total sales amount by multiplying quantity and price

Solution

1. Step 1: Understand the multiplication operator in DAX

   The asterisk (*) symbol multiplies two numbers or columns in DAX.

2. Step 2: Analyze the expression components

   SUMX(Sales, Sales[Quantity] * Sales[Price]) iterates over Sales table, multiplies Quantity and Price row-by-row, and sums the results.

3. Final Answer:

   The total sales amount by multiplying quantity and price -> Option D

4. Quick Check:

   Quantity * Price = Total Sales [OK]

Hint: Multiply quantity and price to get total sales [OK]

Common Mistakes:

• Confusing multiplication with addition
• Using division instead of multiplication
• Ignoring the column context in calculation

2. Which of the following is the correct syntax to create a new measure that subtracts Discount from TotalPrice in DAX?

easy

A. NewMeasure = TotalPrice + Discount

B. NewMeasure := TotalPrice - Discount

C. NewMeasure = TotalPrice - Discount

D. NewMeasure - TotalPrice - Discount

Solution

1. Step 1: Recall the correct assignment operator in DAX

   DAX uses the equals sign (=) to assign expressions to measures.

2. Step 2: Check the arithmetic operator for subtraction

   The minus sign (-) subtracts one value from another.

3. Final Answer:

   NewMeasure = TotalPrice - Discount -> Option C

4. Quick Check:

   Use '=' for assignment and '-' for subtraction [OK]

Hint: Use '=' to assign and '-' to subtract in DAX [OK]

Common Mistakes:

• Using ':=' instead of '=' for measure assignment
• Using '+' instead of '-' for subtraction
• Missing the assignment operator

3. Given the DAX measure:
Profit = SUM(Sales[Revenue]) - SUM(Sales[Cost])
and the Sales table has Revenue = 1000 and Cost = 700,
what is the value of Profit?

medium

A. 1700

B. 300

C. 700

D. 1000

Solution

1. Step 1: Calculate the sum of Revenue

   SUM(Sales[Revenue]) = 1000 as given.

2. Step 2: Calculate the sum of Cost and subtract

   SUM(Sales[Cost]) = 700, so Profit = 1000 - 700 = 300.

3. Final Answer:

   300 -> Option B

4. Quick Check:

   Revenue - Cost = 300 [OK]

Hint: Subtract total cost from total revenue to get profit [OK]

Common Mistakes:

• Adding instead of subtracting
• Using individual row values instead of sums
• Confusing Revenue and Cost columns

4. Identify the error in this DAX measure:
NetAmount = SUM(Sales[Amount]) + - SUM(Sales[Discount])

medium

A. No error, the syntax is correct

B. Missing parentheses around SUM functions

C. SUM function cannot be used with columns

D. Incorrect use of '+ -' operators together

Solution

1. Step 1: Analyze the operator usage

   The '+ -' uses unary minus after addition, which is valid in DAX.

2. Step 2: Verify the expression

   SUM(Sales[Amount]) + (-SUM(Sales[Discount])) correctly computes net amount as Amount minus Discount.

3. Final Answer:

   No error, the syntax is correct -> Option A

4. Quick Check:

   SUM(Amount) + -SUM(Discount) = Net Amount [OK]

Hint: '+ -' is valid unary minus for subtraction [OK]

Common Mistakes:

• Thinking '+ -' is invalid syntax
• Assuming parentheses are always required around SUM
• Thinking SUM can't be used on columns

5. You want to create a measure that calculates the average price after applying a 10% discount on the Price column. Which DAX expression correctly applies this?

hard

A. AvgDiscountedPrice = AVERAGEX(Sales, Sales[Price] * 0.9)

B. AvgDiscountedPrice = AVERAGE(Sales[Price] * 0.9)

C. AvgDiscountedPrice = SUM(Sales[Price * 0.9]) * 0.9 / COUNT(Sales[Price])

D. AvgDiscountedPrice = SUM(Sales[Price] * 0.9) / COUNT(Sales[Price])

Solution

1. Step 1: Understand the requirement

   We need the average of prices after applying a 10% discount on each price (row context).

2. Step 2: Analyze each option

   Averaging requires row-by-row computation for expressions: AVERAGEX(Sales, Sales[Price] * 0.9) correctly iterates and averages discounted prices. A, C, and D have syntax errors (aggregate on expression without iterator or invalid column reference).

3. Final Answer:

   AvgDiscountedPrice = AVERAGEX(Sales, Sales[Price] * 0.9) -> Option A

4. Quick Check:

   Use AVERAGEX for average of row expressions [OK]

Hint: Apply discount inside AVERAGEX to get correct result [OK]

Common Mistakes:

• Using AVERAGE on expression without iterator
• Using SUM and COUNT instead of AVERAGEX
• Invalid column references like [Price * 0.9]