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MDX Essentials: Basic Set Functions: Subset Functions: The Head() Function - Page 6

May 10, 2004



Another Example



Let's construct a query to meet another hypothetical business need, and to practice what we have learned further. Let's say that Logistics Department, very pleased with the metrics that we provided in our initial example, rewards us fully in the way that only information consumers can: they contact us with a more elaborate requirement.



It seems that Logistics would like to be able to present, within a single report, the difference in total Units Shipped and Units Ordered for the first two Quarters of 1998, preferring that we label this derived metric Volume Delta. They want to see the measures for the Washington Warehouse-Cities only, at least in this request. Further, they want to see this information presented in such a way that the Units Shipped, Units Ordered and Volume Delta values are side-by-side, for easy verification of the new variance amount.



We will return to the MDX Sample Application, creating a new query to handle this request.



1. Select File --> New to create a new MDX query.

A blank Query pane appears.

2. Type the following query into the Query pane:


-- MDX019-5, Use of Head() Function - Bonus Example
WITH 

   MEMBER [Measures].[Volume Delta] AS

     '[Measures].[Units Ordered] -  [Measures].[Units Shipped]'

SELECT

   CROSSJOIN (

       {HEAD([Time].[Year].[1998].Children, 2)},

           {[Measures].[Units Ordered], [Measures].[Units Shipped], 

                [Measures].[Volume Delta]} ) ON COLUMNS,

       {[WAREHOUSE].[Country].[USA].[WA].Children} ON ROWS

FROM

    [Warehouse]

In the query above, we use the WITH keyword to create a calculated measure, to act as our new derived Volume Delta measure. In addition, we exploit the CrossJoin() function to order our three measures under each Quarter we present. Finally, we use the Head() function, once again, to retrieve the first two Quarters of 1998 for our column axis.

NOTE: For details concerning calculated measures, see my articles index at Database Journal.com. For information about the CrossJoin() function, see my article Basic Set Functions: The CrossJoin() Function.

3. Execute the query by clicking the Run Query button in the toolbar.

The Results pane is populated by Analysis Services, and the dataset shown in Illustration 9 appears.


Illustration 9: Result Dataset

We see Q1 and Q2 populating the columns across, together with the Units Shipped, Units Ordered and Volume Delta measures aligned under each. In addition, the Washington Warehouse-Cities appear in the row axis, as required by the information consumers in Corporate Logistics.

4. Select File -> Save As, name the file MDX19-5, and place it in a meaningful location.

5. Close the Sample Application when ready.

Summary ...

This article served as the beginning of a set of three articles surrounding subset functions. We introduced the Head() function, whose general purpose is to return a specified number of elements in a set, preserving natural order. We commented upon the operation of the function, and then examined its syntax.

We undertook practice examples with the function, within which we acted to meet illustrative business requirements. We demonstrated the manner in which the Head() function handles various numeric expression input scenarios. Throughout the practice examples, we briefly discussed the results datasets we obtained with regard to the Head() function, together with other surrounding considerations.

We will continue our "triptych" surrounding subset functions in our next article, where we will examine the Tail() function. The last of these three articles will focus on the Subset() function. The objective of covering the three subset functions in close proximity is to emphasize their commonalities from the perspective of usage and operation; once we have dedicated our attention to each in turn, we will be able to more finely distinguish among them for the attributes we need to leverage to meet specific business needs.

» See All Articles by Columnist William E. Pearson, III

Discuss this article in the MSSQL Server 2000 Analysis Services and MDX Topics Forum.

MDX Essentials Series
The LEVEL_NUMBER Member Property
The LEVEL_UNIQUE_NAME Intrinsic Member Property
Intrinsic Member Properties: The HIERARCHY_UNIQUE_NAME Property
Intrinsic Member Properties: The DIMENSION_UNIQUE_NAME Property
Further Combination of BottomCount() with Other MDX Functions
Combine BottomCount() with Other MDX Functions to Add Sophistication
Basic Set Functions: The BottomCount() Function, Part I
Intrinsic Member Properties: The MEMBER_VALUE Property
Intrinsic Member Properties: The MEMBER_UNIQUE_NAME Property
Intrinsic Member Properties: The MEMBER_NAME Property
Intrinsic Member Properties: The MEMBER_KEY Property
Intrinsic Member Properties: The MEMBER_CAPTION Property
Set Functions: The StripCalculatedMembers() Function
Set Functions: The AddCalculatedMembers() Function
MDX Numeric Functions: The Min() Function
MDX Numeric Functions: The Max() Function
Set Functions: The .AllMembers Function
MDX Essentials: Set Functions: The MeasureGroupMeasures() Function
String Functions: The .Properties Function, Part II
String Functions: The .Properties Function
Logical Functions: IsGeneration(): Conditional Logic within Filter Expressions
MDX Scripting Statements: Introducing the Simple CASE Statement
Logical Functions: IsGeneration(): Conditional Logic within Calculations
Logical Functions: IsAncestor(): Conditional Logic within Filter Expressions
MDX Clauses and Keywords: Use HAVING to Filter an Axis
Logical Functions: IsAncestor(): Conditional Logic within Calculations
Logical Functions: IsSibling(): Conditional Logic within Filter Expressions
Logical Functions: IsSibling(): Conditional Logic within Calculations
MDX Operators: The IsLeaf() Operator: Conditional Logic within Filter Expressions
MDX Operators: The IsLeaf() Operator: Conditional Logic within Calculations
MDX Numeric Functions: The .Ordinal Function
Other MDX Entities: Perspectives
MDX Operators: The IS Operator
MDX Set Functions: The Distinct() Function
MDX Set Functions: The ToggleDrillState() Function
Set Functions: The DrillUpLevel() Function
Set Functions: The DrillDownLevelTop() and DrillDownLevelBottom() Functions
MDX Set Functions: DrillDownLevel()
MDX Set Functions: The DRILLUPMEMBER() Function
MDX Essentials: Set Functions: The DRILLDOWNMEMBERTOP() and DRILLDOWNMEMBERBOTTOM() Functions
MDX Essentials : Set Functions: The DRILLDOWNMEMBER() Function
MDX Essentials: Drilling Through with MDX: The DRILLTHROUGH Statement
MDX Essentials: String Functions: The .UniqueName Function
MDX Essentials: String Functions: The .Name Function
MDX Essentials: String / Numeric Functions: The CoalesceEmpty() Function
MDX Essentials: Basic Set Functions: The TopCount() Function, Part II
MDX Essentials: Basic Set Functions: The TopCount() Function, Part I
MDX Essentials: Enhancing CROSSJOIN() with Calculated Members
MDX Essentials: Set and String Functions: The GENERATE() Function
MDX Essentials: The CROSSJOIN() Function: Breaking Bottlenecks
MDX Essentials: String / Numeric Functions: More on the IIF() Function
MDX Essentials: String / Numeric Functions: Introducing the IIF() Function
MDX Essentials: Logical Functions: The IsEmpty() Function
MDX Essentials: Basic Set Functions: The EXTRACT() Function
MDX Essentials: Numeric Functions: Introduction to the AVG() Function
MDX Essentials: Basic Member Functions: The .Item() Function
MDX Essentials: Basic Set Functions: Subset Functions: The Subset() Function
MDX Essentials: Basic Set Functions: Subset Functions: The Tail() Function
MDX Essentials: Basic Set Functions: Subset Functions: The Head() Function
MDX Essentials: Basic Set Functions: The CrossJoin() Function
MDX Essentials: Basic Numeric Functions: The Count() Function
MDX Essentials: Basic Set Functions: The Filter() Function
MDX Essentials: Basic Set Functions: The EXCEPT() Function
MDX Essentials: Basic Set Functions: The Intersect() Function
MDX Essentials: Basic Set Functions: The Union() Function
MDX Essentials: Basic Set Functions: The Order() Function
MDX Essentials - MDX Time Series Functions, Part III: The LastPeriods() and ParallelPeriod() Functions
MDX Time Series Functions, Part II: The OpeningPeriod () and ClosingPeriod() Functions
MDX Essentials - MDX Time Series Functions, Part I: PeriodsToDate() and Kindred Functions
MDX Essentials: MDX Member Functions: "Relative" Member Functions
MDX Member Functions: The Cousin () Function
MDX Essentials: Member Functions: More "Family" Functions
MDX Member Functions: The "Family" Functions
MDX Essentials: MDX Members: Introducing Members and Member
MDX Essentials : MDX Operators: The Basics
MDX Essentials: Structure of the MDX Data Model
MDX at First Glance: Introduction to SQL Server MDX Essentials








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