Introduction to the "Family"
Member Functions
In the first lesson of
the Member Functions segment of our series, we will take some
time to "get to know the family." I like to call one specific subset
of the member functions and operators the "family" functions, because
many of their names resemble those of family members. The functions that
compose this group include:
-
.Parent
-
.Children
-
Ancestor()
-
Cousin()
-
.FirstChild
-
.LastChild
-
.FirstSibling
-
.LastSibling
The "family"
metaphor is appropriate, because these functions perform operations on
dimensions, hierarchies, and levels in a manner that mirrors movement about a "family
tree." There are other "family" functions that return sets, but
we will focus primarily on the member functions in this segment of the
series.
We
will discuss some of the concepts that underlie the "family"
functions, and discuss the appropriate syntax involved in using each
effectively. Next, we will provide hands-on exposure to the use of each in
simple expressions / queries that we will subsequently run to view the output
and reinforce our understanding of the function / component from the perspective
of the result dataset that it returns.
This lesson will
include:
- Further general discussion surrounding members and
member functions and their roles in MDX, when relevant to the
component under consideration.
- An introduction to the .Parent, .Children
and Ancestor() functions, with
- an examination of the syntax that surrounds each function's
use;
- an illustrative example of its use in a practice
exercise;
- a brief discussion of the MDX results we obtain in the
practice example.
- An introduction to the WHERE clause, and the specification
of slicer dimensions.
- A look ahead to the additional member "family"
functions that we will explore in forthcoming articles.
As we mentioned in Lesson
4, member functions, particularly those of the "family"
group, allow us to perform operations based upon a member's relative
position, either up ("above" the member upon which the function
is being performed) or down ("below" the member upon which the
function is being performed) a dimensional hierarchy. A zero is returned if we
attempt to go beyond the boundaries of a defined hierarchy an example of this
might be trying to apply the .Children function to a member at the
bottom / leaf level of the hierarchy (which is childless, in this context).
Like most member functions, the "family" functions can be quite
valuable in helping us to simplify our MDX queries and make them more compact.
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