Chapter 4: An Introduction to Data Analysis Expressions (DAX)

  Understanding the Basics of DAX

What is DAX?

DAX stands for Data Analysis Expressions. It is a formula language used in Power BI to create new insights from existing data.

DAX is to Power BI what formulas are to Excel.

Excel Formula:
=IF(A1 > 10, "Yes", "No")

DAX Formula:
= IF([Sales] > 10000, "Yes", "No")

Both perform similar logic, but DAX works on entire tables, not individual cells.

Where is DAX Used in Power BI?

Use Case	What You Create	Example
New field in table	Calculated Column	Mark product as High or Low
Summary value	Measure	Total Sales, Avg Profit
Custom table	Calculated Table	Top 5 Products

Why Do We Need DAX?

Power BI by default shows basic aggregations like sums, counts, and averages. However, real business analysis needs advanced logic.

• Show sales where profit margin is over 30%
• Group customers into Gold, Silver, Bronze
• Compare current month sales with last year

This is where DAX becomes essential.

Real-World Example

Customer	Sales	Target
A	8000	10000
B	12000	10000

DAX Formula:

Target Met = IF([Sales] >= [Target], "Yes", "No")

Customer	Target Met
A	No
B	Yes

What is a KPI in Power BI?

KPI (Key Performance Indicator) measures how well a goal or target is achieved.

DAX KPI Example:
KPI_Sales_Achievement = DIVIDE([Total Sales], [Sales Target])

KPIs provide quick insights using visuals like indicators, targets, and trend arrows.

DAX Is the Brain of Power BI

• Adds intelligence to reports
• Implements business logic
• Works with filters, slicers, and relationships
• Enables KPIs, comparisons, and advanced analytics