Intrinsic Member Properties: The MEMBER_KEY Property

June 20, 2008

About the Series …

This article is a member of the series, MDX Essentials. The series is designed to provide hands-on application of the fundamentals of the Multidimensional Expressions (MDX) language, with each tutorial progressively adding features designed to meet specific real-world needs.

For more information about the series in general, as well as the software and systems requirements for getting the most out of the lessons included, please see my first article, MDX at First Glance: Introduction to MDX Essentials.

Note: Current updates are assumed for MSSQL Server, MSSQL Server Analysis Services, and the related Books Online and Samples.

Overview

In this lesson, we will examine MEMBER_KEY, an intrinsic member property. MEMBER_KEY. As we noted in Intrinsic Member Properties: The MEMBER_CAPTION Property, the intrinsic member properties supported by SQL Server 2005 Analysis Services are of two types: context sensitive member properties and non-context sensitive member properties. MEMBER_KEY belongs to the second group of properties. As a general group, intrinsic member properties provide additional information that can be used by applications to enhance the user's experience. Support for the non-context sensitive member properties is the same for all members, regardless of individual context.

The purpose of the MEMBER_KEY property is to support the return of the member key, in the original data type, for the member with which it is associated. MEMBER_KEY can be useful in a host of different applications, particularly in scenarios where backward compatibility is a consideration; and as I have noted to be the case for other functions and properties within the MDX Essentials series, MEMBER_KEY allows us to exercise a great deal of presentation “sleight of hand,” in working with MDX in Analysis Services, as well as within Reporting Services and various other reporting applications that can access an Analysis Services cube.

The MEMBER_KEY property can be leveraged in activities that range from generating simple lists to supporting sophisticated presentations. It is a particularly effective tool when we need to provide parameter picklist support (where it can serve multiple purposes, such as an index) and the like, as we shall see. We will introduce the function, commenting upon its operation and touching upon examples of effects that we can employ it to deliver. As a part of our discussion, we will:

  • Examine the syntax surrounding the function;
  • Undertake illustrative examples of the uses of the function in practice exercises;
  • Briefly discuss the results datasets we obtain in the practice examples.

The MEMBER_KEY Property

Introduction

According to the Analysis Services Books Online, the MEMBER_KEY property specifies “…The value of the member key in the original data type. MEMBER_KEY is for backward-compatibility.” The Books Online further state that the “… MEMBER_KEY has the same value as KEY0 for non-composite keys, and MEMBER_KEY property is null for composite keys.”

MEMBER_KEY has many applications, including the rather obvious uses with Analysis Services members that are included in the definition, as well as its pairing with other MDX functions to leverage its power even further. As we have seen is the case with the .Name function (among others), as well as the MEMBER_CAPTION property, in other articles of this series, MEMBER_KEY can also be synergistically combined with the .CurrentMember function; we will see an example of this combination within the practice exercises that follow.

We will examine the syntax involved in leveraging the MEMBER_KEY property after our customary overview in the Discussion section that follows. After that, we will conduct a practice example, within a scenario constructed to support a hypothetical business need that illustrates uses for the property. This will afford us an opportunity to explore some of the presentation options that MEMBER_KEY can offer the knowledgeable user. Hands-on practice with MEMBER_KEY, where we will create expressions that leverage the function, will help us to activate what we learn in the Discussion and Syntax sections that follow.

Discussion

To restate our initial explanation of its operation, the MEMBER_KEY property, when acting upon a member, returns the member key of the object to which it is appended with the period (“.”) delimiter. The value returned is null for composite keys, and equates to a “.KEY0” use of the KEY(x) property (which, as we learn within the respective article within this series, returns the zero-based ordinal of the key) for non-composite keys. MEMBER_KEY can be used for a great deal more than the support of simple lists of unique object names, as we have intimated. When we couple it with other functions, we can leverage MEMBER_KEY to deliver a wide range of analysis and reporting utility.

As in so many cases with the Microsoft integrated business intelligence solution, consisting of MSSQL Server, Analysis Services and Reporting Services, this property, properly exploited within the Analysis Services layer, can be extended to support capabilities and attributes in the Reporting Services layer. Knowing “where to put the intelligence” among the various layers is critical to optimization, in many cases. For more of my observations on this subject, see Multi-Layered Business Intelligence Solutions ... Require Multi-Layered Architects.

The MEMBER_KEY property returns, as we have noted, a typed key associated with the member. If we are using MEMBER_KEY in conjunction with a member with which a composite key is associated, a null value is returned.

Let’s look at a syntax illustration to further clarify the operation of MEMBER_KEY.

Syntax

Syntactically, anytime we employ the MEMBER_KEY property to return the associated key, the member for which we seek to return the key is specified to the left of MEMBER_KEY. The property takes the object to which it is appended as its argument, and returns, in the original data type, the key of the object specified. The general syntax is shown in the following string:

<<Member_Expression>>.MEMBER_KEY

In short, putting MEMBER_KEY to work couldn’t be easier. When specifying the property to return the Key of a member or members, we simply append it to the right of the member(s) under consideration.

As is typically the case with MDX functions, operators and properties, the MEMBER_KEY property can often be best leveraged by combining it with other functions, operators or properties, particularly “relative” functions, to generate lists of names, and so forth, as we shall see in short order.

NOTE: For information on several of the “relative” functions, see my article MDX Member Functions: "Relative" Member Functions, within the Database Journal MDX Essentials series.

We will practice some uses of the MEMBER_KEY property in the section that follows.








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