Advanced Modeling - Microsoft SQL Server 2008 Analysis Services - page 90

NOTE
Defining attributes as parents provides flexible functionality. However, be careful about
using this capability; you can get into trouble with too much flexibility. For example, the
number of levels in a hierarchy can change based on the data.

Parent-Child Hierarchies

The last hierarchy we want to discuss is the hierarchy whose definition is based on the
Parent attribute. (For details about Parent attributes, see the section “Parent Attributes” in
Chapter 5, “Dimensions in the Conceptual Model.”) When you're creating a parent-child
hierarchy, the parent attribute goes on top of the regular attribute that will play the role of
the child of the parent attribute.

The parent and child attributes form a special hierarchy. In the simplest case, the parent-
child hierarchy contains only two attributes: the parent attribute, and the key attribute,
which acts as a child attribute. At this time, this type of parent-child hierarchy is the only
one supported by Analysis Services.

Figure 8.3 shows an example of a parent-child hierarchy based on our sample Employee
attribute in the Employees dimension. In the figure, we can see the hierarchy built on this
attribute in both a diagram and an actual hierarchy from FoodMart.

FIGURE 8.3

This hierarchy is based on the Employees attribute of the Employee dimension.