SQL Server Analysis Services

MDX Functions

Multidimensional Expressions (MDX) is a query language for OLAP data that is used by SQL Server Analysis Services. MDX functions provide a rich set of capabilities for data manipulation, calculation, and analysis within the multidimensional model.

Function Categories

MDX functions can be broadly categorized based on their purpose:

• Aggregate Functions: Used to perform calculations across a set of data, such as SUM, AVG, COUNT.
• Numeric Functions: Perform mathematical operations and return numeric values.
• String Functions: Manipulate and return string values.
• Set Functions: Operate on sets of members or tuples, returning new sets or modifying existing ones.
• Date and Time Functions: Work with date and time values.
• Information Functions: Provide information about the cube structure or query context.
• Type Conversion Functions: Convert values from one data type to another.

Commonly Used MDX Functions

Here are some frequently used MDX functions:

• SUM()

  Calculates the sum of numeric expressions evaluated over a specified set.

  SUM(Set_Expression, Numeric_Expression)

  Example: SUM({[Date].[Calendar Year].&[2023]}, [Measures].[Sales Amount])

• AVG()

  Calculates the average of numeric expressions evaluated over a specified set.

  AVG(Set_Expression, Numeric_Expression)

  Example: AVG({[Product].[Category].&[Electronics]}, [Measures].[Unit Price])

• COUNT()

  Counts the number of elements in a set or the number of non-null values in an expression.

  COUNT(Set_Expression, Numeric_Expression)

  Example: COUNT([Customer].[Customer Name].Members)

• HEAD()

  Returns the first N elements of a set.

  HEAD(Set_Expression, Numeric_Expression)

  Example: HEAD([Date].[Month].Members, 3)

• TAIL()

  Returns the last N elements of a set.

  TAIL(Set_Expression, Numeric_Expression)

  Example: TAIL([Product].[Product Name].Members, 5)

• IIF()

  Returns one of two values, depending on whether a logical expression evaluates to TRUE or FALSE.

  IIF(Logical_Expression, Value_If_True, Value_If_False)

  Example: IIF([Measures].[Profit] > 0, "Profitable", "Loss")

• CASE

  Enables conditional logic, similar to IF statements in other languages.

  CASE WHEN Condition1 THEN Result1 [WHEN Condition2 THEN Result2] [ELSE ElseResult] END

  Example: CASE WHEN [Measures].[Sales] > 1000 THEN "High Sales" WHEN [Measures].[Sales] > 500 THEN "Medium Sales" ELSE "Low Sales" END

Accessing Function Documentation

For detailed information on each MDX function, including syntax, arguments, return values, and examples, please refer to the specific documentation pages:

• MDX Aggregate Functions
• MDX Numeric Functions
• MDX String Functions
• MDX Set Functions