DAX Basics

Before learning advanced DAX functions, it's important to understand how DAX formulas are written.

DAX formulas consist of expressions that reference tables, columns, measures, operators, and functions.

Understanding these building blocks makes writing calculations much easier.

DAX Formula Structure

Most DAX formulas follow this pattern:

Measure Name =
Expression

Example:

Total Sales =
SUM(FactSales[SalesAmount])

Everything to the left of the equals sign is the measure name.

Everything to the right is the expression that Power BI evaluates.

Tables and Columns

DAX references data using table and column names.

The syntax is:

TableName[ColumnName]

Example:

SUM(FactSales[SalesAmount])

Here:

• FactSales is the table.
• SalesAmount is the column.

Measures

Measures are referenced using square brackets only.

Example:

Profit Margin =
DIVIDE(
    [Total Profit],
    [Total Sales]
)

Notice that measures do not include the table name.

Constants

DAX supports numeric, text, date, and Boolean constants.

Examples:

100
3.14
"North"
TRUE()
FALSE()
DATE(2026,1,1)

Constants are often used inside calculations.

Arithmetic Operators

Example:

Total Cost =
SUM(Sales[Quantity]) * 25

Comparison Operators

Comparison operators return TRUE or FALSE.

Example:

IF(
    [Total Sales] > 100000,
    "High",
    "Low"
)

Logical Operators

DAX also supports logical operations.

Example:

IF(
    Sales[Quantity] > 10 &&
    Sales[SalesAmount] > 500,
    "Large Order",
    "Standard Order"
)

Comments

Single-line comments begin with two forward slashes.

// Calculate total sales
Total Sales =
SUM(FactSales[SalesAmount])

Block comments can also be used.

/*
Revenue calculations
for monthly reporting
*/

Comments improve readability and maintainability.

Functions

Functions perform calculations.

General syntax:

FUNCTION(argument1, argument2, ...)

Example:

SUM(FactSales[SalesAmount])

Here:

• SUM is the function.
• FactSales[SalesAmount] is the argument.

Nesting Functions

Functions can be combined together.

Example:

Profit Margin =
DIVIDE(
    SUM(FactSales[Profit]),
    SUM(FactSales[SalesAmount])
)

The SUM() functions execute before DIVIDE() returns the final result.

DAX Is Case Insensitive

These formulas are equivalent:

SUM(FactSales[SalesAmount])

sum(FactSales[SalesAmount])

However, using proper capitalization improves readability.

Best Practices

When writing DAX:

• Use descriptive measure names.
• Keep formulas readable.
• Format complex calculations across multiple lines.
• Reuse existing measures whenever possible.
• Add comments for complex business logic.

Readable DAX is easier to debug and maintain.

Next Steps

Continue learning:

• Measures
• Calculated Columns
• Filter Context
• CALCULATE Function