Database Reference
In-Depth Information
Table
14-1
lists common MDX dimension terms and definitions. These terms are important to understand,
because we use them to discuss MDX report queries.
Table 14-1.
MDX Concepts
Concept
Description
Details/Examples
Dimensions
A way of grouping attributes.
Title names and publisher names are values.
Dimensions are groupings of these values.
Measures
A column of values in the fact table
described by the dimensional keys.
Each measure represents a column or
calculated column from a fact table. An
example is SalesQuantity from our fact table
in the DWPubsSales data warehouse.
Member
Individual attributes of a dimension,
hierarchy, or level. Each attribute
within a hierarchy is a member.
Let's say you have a Date dimension with the
levels of Years, Quarters, and Months; June
would be an individual member of the Month
level.
Measures dimension
The special dimension that all
measures are grouped within.
The Measures dimension has only a single
level and does not include an
All
level/member.
Measure groups
A way of organizing measures.
One SSAS cube can contain many measure
groups.
All member
A grand total of all items within
a dimension (not including the
Measures dimension).
Every dimension (except the Measures
dimension) has an All member. For example,
in the Date dimension of Figure
14-1
, there is
an implied All Dates member.
Attribute
The property of a member or
combination of members.
Attributes in SSAS are mapped to one or more
columns in your data warehouse tables. For
example, the Date key and the Date name
combine to make up the Date attribute
within the Date dimension. In MDX you can
reference an attribute by either its key or its
name.
Hierarchy
The manner in which data is grouped
together and structured into levels.
For example, dates may be grouped by
months, months by quarters, and quarters by
years. Each dimension (except the Measures
dimension) is made up of one or more
hierarchies. For example, titles are grouped in
one hierarchy by publishers and in a second
hierarchy by types, creating more than one
hierarchy.
Parent
The family relationship within a
hierarchy that lower-level members
are derived from.
For example, the month of January 1992 is the
parent of the date January 1, 1992.
(
continued
)
