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MDX – Generic Averages

October 6, 2013 Leave a comment

In most the business scenarios, Averages play a major role for analysis. It is certain that we have 2 different kinds of averages from OLAP perspective.

1. Average of measures from its immediate children
2. Average of measures from its lower level children i.e. From Grain of the Fact table
a. Using Recursive
b. Using Descendant children count
Here planning to discuss these two averages and making the Generic MDX so ready to use for any measure and dimension in any OLAP Cubes.
Have provided complete working query with all steps and comments for more info

WITH 
// STEP 1: Current Member Children Count 
// Reusable code to any Row members
MEMBER [Measures].[Child Count] AS 
SUM( 
	Axis(1).Item(0).Item(0).Hierarchy.CurrentMember.Children,
		IIf(
			Axis(0).Item(0) = 0,
			NULL,
			1
		   )   
	)
// STEP 2: Average of CurrentMember
// Reusable code to any Row members and Column Measure
MEMBER [Measures].[Average Measure (Using Children)] AS
    iif( IsEmpty(Axis(0).Item(0)),
         null,
            iif( Axis(1).Item(0).Item(0).Hierarchy.CurrentMember.Level.Ordinal = 0,
                   Axis(0).Item(0),        
                   Sum(Axis(1).Item(0).Item(0).Hierarchy.CurrentMember.Children,
                       Axis(0).Item(0)
					   )
                       /
                        Count(NonEmpty(Axis(1).Item(0).Item(0).Hierarchy.CurrentMember.Children,
                                       Axis(0).Item(0)
									   )
							 )                                
               )
        )       
, FORMAT_STRING = 'Currency'

// STEP 3: Average of CurrentMember Recursive
// Used Child Count from STEP 1
// Reusable code to any Row members and Column Measure
MEMBER [Measures].[Average Measure (ExplicitRecursive)] AS
	IIF(
		[Measures].[Child Count] <= 1
		,Axis(0).Item(0)
		,SUM(
				{ Axis(1).Item(0).Item(0).Hierarchy.CurrentMember.Children },
				( [Measures].[Average Measure (ExplicitRecursive)] )
		    ) 
		    /
		    [Measures].[Child Count]
	   ),
	FORMAT_STRING="Currency"
// STEP 4: Child Count using DESCENDANTS
// This requires Row Members so no more dynamic
MEMBER [Measures].[Child Count (Using DESCENDANTS)] AS 
 SUM( 
		DESCENDANTS(
		 [Date].[Calendar].CurrentMember,	
		 [Date].[Calendar].[Month]				
	    )
		,IIF( Axis(0).Item(0) = 0 OR IsEmpty(Axis(0).Item(0))
		, NULL
		, 1
	 )
	)
// STEP 5: Average of CurrentMember using Child Count FROM STEP 4
// Reusable code to any Row members and Column Measure
MEMBER [Measures].[Average Measure (Using ChildCountDESCENDANTS)] AS
 DIVIDE(Axis(0).Item(0),[Measures].[Child Count (Using DESCENDANTS)] )
, FORMAT_STRING = 'Currency'

	SELECT	{
		[Measures].[Reseller Sales Amount],
		[Measures].[Child Count],
		[Measures].[Average Measure (Using Children)],		
		[Measures].[Average Measure (ExplicitRecursive)],		
		[Measures].[Child Count (Using DESCENDANTS)],
		[Measures].[Average Measure (Using ChildCountDESCENDANTS)]	
	} ON COLUMNS,
	
	{
		DESCENDANTS(
			[Date].[Calendar].[Calendar Year].&[2007],
			[Date].[Calendar].[Month],
			SELF_AND_BEFORE
		)
	} ON ROWS 
FROM	[Adventure Works]

Generic Averages

Points to consider:

1. Provided two different generic MDX calculations and it is better to adopt the method suitable to project with performance as major consideration
2. Recursive method is more powerful and equally confusing to need to understand the bottom line before implementing
3. I think, this is more useful in any Business domain requiring averages’ analysis

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