# What is a DAX Expression?

### Basic DAX Syntax

A DAX formula is comprised of an equal sign followed by a function or expression.

• Functions perform operations such as concatenating or adding values, calculating sums or averages, or performing logical tests. Functions usually take some kind of argument, which might be a reference to a column or table. Functions can be nested inside other functions.
• An expression can be used to define a value that can be a literal value or constant, a Boolean test, or a reference to a column containing values. Boolean expressions can be used to define a filter condition, such as [Sales] > 100.
• Operators within expressions, such as a plus or minus sign, indicate how the values are to be compared or processed.
• Values that you use in formulas and expressions can be typed directly into the formula bar as part of an expression, or they can be obtained from other columns, tables, or formulas. However, you cannot reference only a few cells or a range of cells; DAX always works with complete columns or tables.

For example, the following formulas are all valid:

• =3
• ="Sales"
• ='All Sales'[Amount]
• =[Amount]*1.10
• =PI()
• ='FALSE' = 0
• =SUMX(FILTER(Sales,Region="Europe"),[SalesAmount])

Summary:

• The formula is the full line.
• A function example is "SUMX".
• An expression can be used to define values.
• An operator is just the sign (=, <, etc.), and a value is just the number/value being defined within the expression or used by the function.

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