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Summary

In this module, you learned how to use DAX to add calculations to your model. You explored three types of calculations:

• Calculated tables
• Calculated columns
• Measures

You also learned the basics of DAX, including:

• Writing formulas
• Using different data types
• Applying functions, operators, and variables
• Referencing model objects and constants

DAX Formulas Knowledge Test - PL-300 Standard

Instructions: This quiz covers all key concepts from "Write DAX formulas for semantic models." Choose the best answer for each question. Solutions are provided at the end.

Section 1: DAX Calculation Types

Question 1

Which DAX calculation type is evaluated at query time and never stored in the model?

A) Calculated Table

B) Calculated Column

C) Measure

D) Row-level Security Rule

Question 2

You need to create a table containing only customers with sales > $10,000 for analysis. Which approach should you use?

A) Create a calculated column in the Customer table

B) Create a calculated table using FILTER function

C) Create a measure with FILTER function

D) Use Power Query to filter the data

Question 3

In a role-playing dimension scenario with OrderDate and ShipDate, what's the recommended approach?

A) Use USERELATIONSHIP function in all calculations

B) Create two separate date tables with active relationships

C) Keep one relationship active and one inactive

D) Create calculated columns for both dates

Question 4

Which statement about calculated columns is FALSE?

A) They are evaluated row by row

B) They increase model storage size in Import mode

C) They are evaluated at query time

D) They can be used to create relationships between tables

Section 2: DAX Formula Structure

Question 5

What is the correct way to reference a column named "Sales Amount" in the "Sales" table?

A) Sales.Sales Amount

B) Sales[Sales Amount]

C) [Sales Amount]

D) "Sales Amount"

Question 6

When should you use single quotes around a table name?

A) Always

B) Never

C) When the table name contains spaces or is a reserved keyword

D) Only for calculated tables

Question 7

Which reference is correct for a measure named "Total Revenue"?

A) Sales[Total Revenue]

B) [Total Revenue]

C) "Total Revenue"

D) Total Revenue

Section 3: DAX Data Types

Question 8

What does the BLANK data type represent in DAX?

A) Zero value

B) Empty string

C) Absence of a value

D) Boolean FALSE

Question 9

In the expression [Revenue] = 0, when will this return TRUE?

A) Only when Revenue equals zero

B) When Revenue equals zero OR is BLANK

C) Only when Revenue is BLANK

D) Never, this syntax is invalid

Question 10

What's the difference between = and == operators?

A) No difference, they work the same

B) == treats BLANK as zero, = does not

C) = treats BLANK as zero, == does not

D) == is used for text, = for numbers

Section 4: DAX Functions

Question 11

Which function should you use to safely perform division and avoid division by zero errors?

A) IF function with error checking

B) DIVIDE function

C) IFERROR function

D) Standard division operator (/)

Question 12

What does the DISTINCTCOUNT function calculate?

A) Total number of rows in a table

B) Number of non-blank values in a column

C) Number of unique values in a column

D) Number of duplicate values in a column

Question 13

Which DAX function would you use to create a date table?

A) DATEADD

B) CALENDAR or CALENDARAUTO

C) DATEDIFF

D) TODAY

Section 5: DAX Operators

Question 14

What is the correct operator precedence order (highest to lowest)?

A) +, -, *, /, ^

B) ^, *, /, +, -

C) *, /, ^, +, -

D) ^, +, -, *, /

Question 15

In the expression Sales[Quantity] * Sales[Price] * 1 - Sales[Discount], what's the issue?

A) Syntax error

B) Wrong operator precedence - should use parentheses

C) Missing table reference

D) No issue, the expression is correct

Question 16

Which logical operator creates an OR condition between expressions?

A) &&

B) ||

C) AND

D) IN

Section 6: DAX Variables

Question 17

What are the main benefits of using VAR in DAX? (Select all that apply)

A) Improved readability

B) Better performance

C) Easier testing of complex formulas

D) Reduced model size

Question 18

In a VAR statement, what keyword is used to define the final expression?

A) END

B) RESULT

C) RETURN

D) OUTPUT

Question 19

Consider this measure:

Revenue YoY % =
VAR RevenuePriorYear =
    CALCULATE([Revenue], SAMEPERIODLASTYEAR('Date'[Date]))
RETURN
    DIVIDE([Revenue] - RevenuePriorYear, RevenuePriorYear)

What does this measure calculate?

A) Revenue for the previous year

B) Revenue difference from previous year

C) Year-over-year revenue percentage change

D) Current year revenue only

Section 7: Advanced Concepts

Question 20

What happens to BLANK values in arithmetic operations?

A) They cause an error

B) They are treated as zero

C) They are ignored

D) They convert to NULL

Question 21

Which statement about implicit vs explicit measures is correct?

A) Implicit measures are written in DAX

B) Explicit measures are automatically created by Power BI

C) Implicit measures use simple aggregations like SUM, COUNT

D) There's no difference between them

Question 22

When creating a calculated table for a role-playing dimension, the new table:

A) Must be related to the original table

B) Should have an active relationship to the fact table

C) Cannot be used in relationships

D) Is automatically created by Power BI

Question 23

Which scenario would require a calculated table rather than a calculated column?

A) Adding a profit margin calculation

B) Creating a customer age group

C) Building a what-if parameter table

D) Concatenating first and last names

Question 24

In DAX, when should you use the IN operator?

A) To check if a value exists in a list of values

B) To perform addition operations

C) To create relationships

D) To define variables

Question 25

What's the recommended approach for formatting complex DAX formulas?

A) Write everything on one line

B) Use spaces, tabs, and line breaks for readability

C) Only use line breaks, no spaces

D) Formatting doesn't matter in DAX

Answer Key & Explanations

Section 1 Answers:

1. C) Measure - Measures are calculated at query time and never stored in the model.

2. B) Create a calculated table using FILTER function - Calculated tables can filter and transform existing data.

3. B) Create two separate date tables with active relationships - This is the recommended approach for role-playing dimensions.

4. C) They are evaluated at query time - FALSE. Calculated columns are evaluated at data refresh time, not query time.

Section 2 Answers:

5. B) Sales[Sales Amount] - Correct syntax uses table name and column in square brackets.

6. C) When the table name contains spaces or is a reserved keyword - Single quotes are needed for special cases.

7. B) [Total Revenue] - Measures should be referenced without table prefixes.

Section 3 Answers:

8. C) Absence of a value - BLANK represents the absence of a value, similar to NULL in SQL.

9. B) When Revenue equals zero OR is BLANK - The = operator treats BLANK as zero.

10. C) = treats BLANK as zero, == does not - Strict equality (==) doesn't treat BLANK as zero.

Section 4 Answers:

11. B) DIVIDE function - DIVIDE automatically handles division by zero cases.

12. C) Number of unique values in a column - DISTINCTCOUNT counts distinct values.

13. B) CALENDAR or CALENDARAUTO - These functions create date tables.

Section 5 Answers:

14. B) ^, *, /, +, - - Exponentiation has highest precedence, then multiplication/division, then addition/subtraction.

15. B) Wrong operator precedence - should use parentheses - Multiplication happens before subtraction, affecting the discount calculation.

16. B) || - Double pipe creates OR condition.

Section 6 Answers:

17. A, B, C) Improved readability, Better performance, Easier testing - All except reduced model size.

18. C) RETURN - RETURN keyword defines the final expression.

19. C) Year-over-year revenue percentage change - The formula calculates YoY percentage change.

Section 7 Answers:

20. B) They are treated as zero - BLANK values are treated as zero in arithmetic operations.

21. C) Implicit measures use simple aggregations like SUM, COUNT - Implicit measures are simple aggregations.

22. B) Should have an active relationship to the fact table - The new table should have an active relationship.

23. C) Building a what-if parameter table - What-if parameters require calculated tables.

24. A) To check if a value exists in a list of values - IN operator checks membership in a list.

25. B) Use spaces, tabs, and line breaks for readability - Formatting improves readability without affecting performance.

Key Study Areas Based on Common Mistakes:

🔍 Focus Areas:

• Operator precedence - Practice complex expressions with parentheses
• BLANK handling - Understand difference between = and ==
• Variable benefits - Know why VAR improves performance and readability
• Calculation types - When to use tables vs columns vs measures
• Function selection - DIVIDE vs /, DISTINCTCOUNT vs COUNT

💡 Pro Tips for PL-300:

• Always use DIVIDE for division operations
• Understand filter context and row context differences
• Practice time intelligence functions
• Know when to use calculated tables vs Power Query
• Master the relationship between measures and filter context