About the Series ...
article is a member of the series Introduction
to MSSQL Server Analysis Services. The series is designed to provide hands-on application of
the fundamentals of MS SQL Server 2005 Analysis Services (Analysis
Services), with each installment progressively presenting features and
techniques designed to meet specific real-world needs. For more information on
the series, please see my initial article, Creating Our First Cube. For the software components, samples and tools
needed to complete the hands-on portions of this article see Usage-Based Optimization in Analysis Services 2005, another article within this
Unknown Members in Analysis Services 2005, Part I, we introduced our topic with discussion surrounding
the fact that, when Analysis Services processes dimensions within a cube,
it attempts to match each dimension key in the fact table with a corresponding
dimension member in the dimension table to which it is joined. We discussed
cases where we might expect to encounter a dimension key existing within the
fact table with no matching key in the dimension table examples include
prototyping and other developmental scenarios, and sometimes after recurring
ETL updates and other evolutions. We mentioned that Analysis Services
employs the concept of an Unknown Member to define such unmatched
dimension members, and then began our hands-on exploration of the management of
the Unknown Member within Analysis Services.
Through discussion and hands-on
procedures, we learned that the Unknown Member settings offer us
capabilities, similar to those found in once dominant enterprise BI
applications such as Cognos PowerPlay / Transformer, for handling
scenarios involving unmatched dimension keys such as we have described. The
capabilities afforded by the Unknown Member options allow us to override
the processing failure that would occur in these cases of mismatch, as well is
to assign a name other than Unknown to Unknown Members within
each dimension, to control visibility of Unknown Members, and more.
Our Part I,
we introduced the general concepts and properties underpinning Unknown
Members, including what they define and support, as well as the mechanics that
lie behind their management. After we had prepared a sample Analysis
Services database and its constituent objects, with which to complete a
hands-on practice session, we performed a review of Unknown Member
properties settings at the dimension level. We then created new attributes
within the Product dimension of our sample cube, upon which our stated
objective was to establish Unknown Member management within the
II, we will continue to gain an introduction and hands-on exposure to
managing Unknown Members within our sample cube. We will resume our
procedures with the sample cube that we created in Part I.
Our continuing examination will include:
where appropriate, of the general concepts and properties (including what they
define and support, and how we can manage them) underpinning Unknown Members.
establishment of Unknown Member management within the associated
supporting properties for the Product dimension attributes that we added
to the sample cube in the first
half of our article.
enhanced Product dimension, and examining the mechanics behind the
default, physical removal of members without corresponding key values within
the underlying data.
discussion of other considerations that surround our management of Unknown
Manage Unknown Members in Analysis Services 2005
briefly summarize what we learned in Manage Unknown Members in Analysis
Services 2005, Part I, when Analysis Services meets with a null value
within the underlying data from which it is attempting to populate a
dimensions attributes, its default reaction is to convert the null to an empty
string (for string columns) or to a zero (for numeric columns).
Also by default, the Analysis Server ignores the error generated
by this condition, allowing processing to continue uninterrupted, removing the attribute
member associated with the null through the action of the inner join performed
between the tables involved. We learned that, while these default settings are
made for us when we use the Dimension and Cube Wizards in
constructing our dimensions, based upon a couple of conditions, we can also
work with certain properties to bring about different treatment of Unknown
Members within our own environments.
discussed three property settings that dictate how the Analysis
Server handles any such null values it encounters in the underlying data. The
first two properties, related to the dimension itself, are UnknownMember
and UnknownMemberName. (We performed an examination of these properties
in our practice session in Part I.) The third property, related to the dimension's
key attribute, is the NullProcessing property. The wizards set
the defaults, based upon the nullability of the items we mention above, to UnknownMember
for the NullProcessing property of the key attribute, Visible for
the UnknownMember property, and a simple Unknown (which we can
easily change, as we shall see, to a name more appropriate for our own
environments) for the UnknownMemberName property. While a fourth
property, NullKeyCovertedToUnknown, is certainly relevant to our
coverage of Unknown Members, its purpose is to direct the Analysis
Server in how it handles the error generated when it encounters
null-valued attribute members (by default, the property is set to IgnoreError,
which, as we noted earlier, directs Analysis Services to remove the
offending attribute member entirely, and to continue processing).
noted that, when we use the Dimension Designer to define a dimension
(versus the wizards), and then add this dimension to our cube, or when we
construct dimensions incrementally, we find that we may need to set some of the
properties manually. Because this is the case, we stated in Part I
that we would focus upon a selected dimension within this context in
the practice sessions of both halves of this article. By taking this approach,
we reasoned that we could concentrate on the properties directly (and a
bit more efficiently), rather than walking through the steps of the wizard to
define a dimension, and then returning to the individual settings to examine
and modify them.
summarize the general steps, once again, we direct the Analysis Server
in how to manage orphan attribute members by enabling the UnknownMember
property for the dimension, and by specifying a value for the UnknownMemberName
property for the dimension (unless the default value of Unknown is
adequate within the local environment). Other actions we might take
surrounding orphan management, as we shall see, include setting attribute
relationships to link dimension attributes appropriately, and
defining custom error handling for the key column used as a basis for
the joins between the fact / dimension tables supporting the dimensional
structure in general.
will continue these steps and others within the practice session that we
undertake in this article.
Establishing Properties to Manage Unknown Members in Analysis Services 2005
restate the business requirement underlying our practice example, as we
established in Part I,
we have received a request for assistance from representatives of our client,
the Adventure Works organization (the details of which we describe in
the first half of our article). In
short, our client colleagues have requested an introduction to the management
of Unknown Members within their implementation of Analysis Services,
stating that they wish to know more about the mechanism behind this process
(they already understand some of the rudiments of default operation by Analysis
Services in this regard). Moreover, they feel that they need some hands-on
guidance in adding a couple of new attributes to their Product
dimension, upon which they intend to base a new user-defined hierarchy
that they have determined they need to support new reporting and analysis requirements
that have been recently requested.
listening carefully to the needs enumerated by our colleagues, we proposed in Part
I to provide an introduction to Unknown
Members in Analysis Services; to provide insight as to the default
operation of the Analysis Server; and to provide practical guidance in
manually managing Unknown Member property settings, via the respective
settings that we establish among the new attribute members and
hierarchical structure we help them to create and configure. Once our client
colleagues agreed that the proposed approach should meet their immediate requirements,
we begin our introduction and set about the assembly of our example to
illustrate both default and manual management of Unknown Members within Analysis
NOTE: Our steps in creating a sample basic database within
which to perform the steps of our practice sessions are detailed in Part
I. Before you can proceed with the
practical steps below, you will need to accomplish the steps outlined in
creating and enhancing the sample cube in Part
Procedure: Continue Working with Properties to Manage Unknown Members in Analysis Services 2005
In the practice session that began
in Part I, we first examined the properties that support
management of Unknown Members. We then added attributes to a
dimension, based upon tables that we added to the underlying data source
the sample Analysis Services database / UDM we had prepared. We then examined
the mechanics behind the default exclusion of unmatched attribute
members within dimension processing.
In this half of the practice
session, we will resume where we left off at the end of Part I, enabling and configuring the
associated properties for the dimension and dimension attributes that we
have added, while discussing our options and the respective results. Finally,
we will manage error handling for the member key attribute involved.
We will perform our practice
session within the SQL Server Business Intelligence Development Studio, as
before, from which we will perform select steps of managing Unknown Members
within the Analysis Services database we created in Part I,
ANSYS063_Basic AS DB.
Reopen SQL Server Business Intelligence
Close the Start
page, if desired.
AS DB database
with which we worked in Part
I is open,
and appears within the Solution Explorer.
Note: For the steps involved in completing the above, see Part I.
re-open the Dimension Designer for the Product dimension, where
we left off in Part I,
and set about modifying the way that Analysis Services manages Unknown
Members by default.
Analysis Services Default Management of Unknown Members through Associated
We will next examine modification of Analysis Services
default management of Unknown Members through the modification of
associated property settings. First, we will enable the UnknownMember
property of the Products dimension. We will then set a value for the UnknownMemberName
property, to generate a name that is more useful to our client colleagues than
a simple Unknown. Next, we will set the NullProcessing
property for the Subcategory and Model Name attributes to UnknownMember.
Our next steps will surround attribute relationships:
We will establish the Category attribute as a related attribute of the Subcategory
attribute, and we will then establish the Product Line attribute as a
related attribute of the Model Name attribute. Our intent with the
steps will be to enforce the use of the specified Unknown Member name
value for any Product that has a key resident in the fact table, but
which has no matching key within the SubcategoryKey column with which we
were working in the earlier section Create New Attributes within the
Product Dimension upon Which to Establish Unknown Member Management within the
Within the Solution
Explorer, right-click the Product dimension (expand the Dimensions
folder as necessary).
on the context menu that appears, as depicted in Illustration 1.
1: Opening the Dimension Designer ...
tabs of the Dimension Designer open.
Click the Dimension
Structure tab, if it has not already appeared by default.
Ensure that Product,
atop the Attribute pane, is selected to cause the dimensions Properties
window to appear (by default in the lower right corner of the design
Within the Properties
window for the Product dimension, change the UnknownMember property
value (within the Advanced properties section of the window) to Visible.
value for the UnknownMemberName property (just beneath the UnknownMember
property value) to Assembly Components.
window for the Product dimension appears, with our modifications, as
shown in Illustration 2.
2: Our Modifications to the Product Dimension Property Settings
Modifying the UnknownMember property from None
(which means that the property is disabled for the dimension) to either Visible
or Hidden enables the property. Our input of Assembly Components
to the UnknownMemberName property assigns our choice of Unknown
Member name value to any Product that has a key resident in the fact
table, but for which the Analysis Server determines that no matching key
exists within the SubcategoryKey column of the associated dimension
table. (This effectively creates what I refer to as an orphan cage.)
Now, lets take a look at the relationships that exist
between certain Product attributes.
following attributes within the Attributes pane of the Dimension
Structure tab for the Product dimension.
expanded attributes appear as depicted in Illustration 3.
Illustration 3: Expanded
Product Attributes in the Attributes Pane
Within the expanded attributes, we note that Product
Line is related to the Model Name attribute (meaning, too, that it
is indirectly linked to the Product Name key attribute). We can see that
no relationships have been defined for the Subcategory attribute.
Moreover, we see that Category attribute is linked to the Product
Name attribute directly through the key attribute.
Our next steps will allow us to enforce the use of our
newly specified Unknown Member name value for any Product that
has a key resident in the fact table, but which has no matching key within the SubCategoryKey
column with which we worked earlier. We will establish a relationship between the
Category attribute and the Subcategory attribute, and then we
will establish the Product Line attribute as a related attribute of the Model
Drag the Category
attribute relationship from the Product Name attribute to the Subcategory
attribute, shown in Illustration 4.
Illustration 4: Modifying
the Relationship from Product Name to Subcategory ...
By taking the above steps, we have linked the Category
attribute to the rows in the fact table through the Subcategory
attribute, which in turn is linked to the rows in the fact table through the Product
In the Attributes
pane, click / select Subcategory.
10. Click the ellipsis button (...)
in the KeyColumns property cell (located within the Source
section) in the Properties window, as depicted in Illustration 5.
Illustration 5: Modifying
KeyColumns Properties for Subcategory ...
11. In the DataItem Collection
Editor dialog that next appears, change the NullProcessing property
to UnknownMember, as shown in Illustration 6.
Illustration 6: Modifying
the NullProcessing Property to UnknownMember ...
12. Click OK to accept our
modification and to dismiss the DataItem Collection Editor dialog.
13. Click / select Model Name within
14. Click the ellipsis button (...)
in the KeyColumns property cell in the Properties window, as we
did for the Subcategory attribute earlier.
15. In the DataItem Collection
Editor dialog that next appears, change the NullProcessing property
to UnknownMember, once again.
16. Click OK to accept our
modification, once again, and to dismiss the DataItem Collection Editor
As we have discussed in earlier sections, these
modifications dictate how Analysis Services handles any nulls it encounters,
during processing, for either or both of the Subcategory attribute or
the Model Name attribute. Our selection of the UnknownMember
option for the NullProcessing property means that the Unknown Member
value (whatever we dictate that to be) will be substituted for the key value.
Hierarchies based upon these members will thereupon reflect the new grouping
for the Unknown Members.
the Product Dimension to Verify the Modified Management of Unknown Members via
the modified dimension, and then leverage the convenience of the built-in Browser
to verify the effects of our handiwork.
the Product dimension within the Solution Explorer.
... from the context menu that appears, as depicted in Illustration 7.
Illustration 7: Process
the Product Dimension ...
when asked if we wish to ... save all changes first.
has successfully completed, click the Browser tab in Dimension
Designer for the Product dimension.
Click the Reconnect
button, once again.
Categories in the Hierarchy list.
Assembly Components appears as a new member of the Category
level, as shown in Illustration 8.
Illustration 8: Assembly
Components Appears as a Member of the Category Level ...
Expand the Assembly
Components member of the Category level.
Expand the Assembly
Components member that appears underneath the Assembly Components
member just expanded (itself a member of the Subcategory level).
We next see all the Assembly Components appearing
at the Product Name level, as partially depicted in Illustration 9.
Illustration 9: Assembly
Components Appears at the Product Name Level Product Category Hierarchy
10. Returning to the Hierarchy
list, select Product Model Lines.
11. Expand All Products.
12. Expand the Assembly Components
member of the Product Line level.
13. Expand the Assembly Components
member of the Model Name level.
We now see the Assembly Components appearing at the
Product Name level, as shown in Illustration 10.
Illustration 10: Assembly
Components Appears at the Product Name Level Product Model Lines Hierarchy
demonstrated the effectiveness of our settings in managing Unknown Members,
and having received confirmation from our client colleagues that their
immediate business requirements have been met through the solution we have demonstrated,
we conclude our two-part practice session. We have established the capability
to manage Unknown Members through settings modifications for a dimension
within our clients cube.
14. Close the Business Intelligence
Development Studio when ready.
In this two-part article, we embarked upon an examination of the
management of Unknown Members within Analysis Services. We noted
that the Unknown Member property settings offer us capabilities, similar
to those found in once dominant enterprise BI applications such as Cognos
PowerPlay / Transformer, for handling unmatched dimension keys. The
capabilities afforded by the Unknown Member options allow us to override
the processing failure that would occur in these cases of mismatch, to assign a
name other than Unknown to the Unknown Member within each
dimension, to control visibility of the Unknown Member, and more.
first half of our article, we gained some exposure to the default management of
Unknown Members by Analysis Services. Our examination included a discussion surrounding the general concepts and
properties underpinning Unknown Members, including what they define and
support, as well as the mechanics behind their management. We then prepared a
sample Analysis Services database with related objects, and began a hands-on
practice session, first reviewing Unknown Member properties settings at
the dimension level. Next we created new attributes within the Product
dimension, upon which we based a user-defined hierarchy, and upon which we intended
to establish, in the second half of the article, Unknown Member management
capabilities within the supporting properties.
processing the enhanced Product dimension and examining the mechanics
behind the exclusion of members without corresponding key values within the
underlying data, we moved to this, Part II, of our article. In this
half, we continued to gain an introduction and hands-on exposure to managing Unknown
Members, resuming our procedures with the sample cube that we
created in Part I.
Our continuing examination included further coverage, where appropriate, of the
general concepts and properties (including what they define and support, and
how we can manage them) underpinning Unknown Members. We established Unknown
Member management within the associated supporting properties for the Product
dimension attributes that we added to the sample cube, at the request of our
client colleagues, in the first half of our article. We then processed the enhanced Product
dimension, and used the Browser within the Dimension Designer
to verify the effectiveness of the results of our work. Finally, throughout
the article we discussed other considerations that surround our management of Unknown
See All Articles by Columnist William E. Pearson, III
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