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MDX Essentials: Basic Set Functions: The EXTRACT() Function - Page 4

October 4, 2004

Procedure

We are now ready to apply the EXTRACT() function to the general population of Product-Store City combinations that we have created with the CROSSJOIN() function in our preparatory steps. We effectively have a set that contains all 1998 Store City Warehouse Sales, filtered, of course, for the empties. To meet the expressed needs of the information consumers with which we are working, we now are faced with extracting fresh Store City tuples, and then presenting the five Store Cities whose products have experienced the highest Warehouse Sales in the 1998 time frame.

1. Insert the EXTRACT() function, as shown:

     EXTRACT(

between the third line of the query (counting the comment line, once again, and shown below):

{[Measures].[Warehouse Sales]} ON COLUMNS,

and the fourth line of the query (which we just added in the last section, as follows):

               FILTER(

2. Insert the following into the line beginning with NOT ISEMPTY , which we also added in the last section, between the last parentheses in the line (just before ON ROWS) and ON ROWS:

                           , [Store]) 

The complete line, together with our addition, should appear as follows:

            NOT ISEMPTY([Measures]. [Warehouse Sales])), [Store])  ON ROWS

With the addition of the EXTRACT() function, together with our specification of the Store dimension in the line ending in ON ROWS, we are, in effect, saying "return a dataset composed of tuples from the Store dimension only." This again generates fresh tuples of only the Store Cities - through the specification of the Store dimension, and the implicit elimination of the Food component from the original tuples.

The Query pane appears as shown in Illustration 4, with additions circled in red.


Illustration 4: Modified Query in Query Pane (Compressed View)

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

The Results pane is populated, and the dataset shown in Illustration 5 appears.


Illustration 5: Results Dataset, With EXTRACT() in Place

We see there are still a total of twenty-three Store Cities; the difference now is that the Food component has vanished. (Actually, the Store City tuples have been created anew, without the Food component that came along with the CROSSJOIN() function earlier).

4.  Select File --> Save to save the query as MDX24-3. Leave the file open for the next step.

5.  Modify the comment line to read:

-- MDX24-4:  Tutorial Query Step 4

6.  Save the file as MDX24-4, to protect MDX24-3.

We have extracted the Store dimension members from the crossjoin-produced original set, and thus are nigh unto meeting the needs of the information consumers. The remaining consideration, to present the five Store Cities whose products have experienced the highest Warehouse Sales, is only a single function away from realization. Let's add the appropriate TOPCOUNT() function and give the users precisely what they have requested.

7.  Insert the TOPCOUNT() function, as shown:

     TOPCOUNT(

Once again, between the third line of the query (shown below):

  {[Measures].[Warehouse Sales]} ON COLUMNS,

And the fourth line of the query (which we just added in the last section, as follows):

               EXTRACT(

8. Insert a comma (,) after [Store]) in the ON ROWS line of the query.

9. Insert the following into the same line, just behind the comma we inserted in the last step, and just before ON ROWS:

5, [Measures].[Warehouse Sales] ) ON ROWS

The complete line, together with our addition, should appear as follows:

NOT ISEMPTY([Measures]. [Warehouse Sales])), [Store]), 
    5, [Measures].[Warehouse Sales] ) ON ROWS

With the addition of the TOPCOUNT() function, together with our specifications of the "5" and the measure Warehouse Sales, in the line ending in ON ROWS, we are saying "return the Store Cities with the top five Warehouse Sales values."

The Query pane appears as depicted in Illustration 6, with additions circled in red.


Illustration 6: Finalized Query in Query Pane (Compressed View)

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

The Results pane is populated, and the dataset shown in Illustration 7 appears.


Illustration 7: Results Dataset, Final Enhancements in Place

We now see the Store Cities, in descending order, with the top five Warehouse Sales values.

11.  Select File --> Save to save the query as MDX24-4.

12.  Exit the Sample Application when ready.

In the forgoing manner we meet an expressed business requirement in a simple example that illustrates the operation of the EXTRACT() function.

Summary ...

In this article, we explored the useful EXTRACT() function, whose purpose is to return a set from an initial set we specify, much in a manner that is opposite to the behavior of the CROSSJOIN() function. The returned set is composed of tuples from dimension(s) that we specify as arguments within the function. We discussed the EXTRACT() function in general, and emphasized its capabilities within MDX, and its usefulness within our analysis toolsets.

In addition to discussing the purpose and operation of the EXTRACT() function, we mentioned the elimination of duplicates by the function. We practiced the use of the function within a multi-step exercise, building an original set in preparation to meet a hypothetical business need. Throughout the steps of the practice exercise, we discussed the results we obtained with each step's execution, remarking on the distinguishing characteristics of each.

» 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
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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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