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Business Intelligence
Notes Also it supports special type of level-based dimension for unbalanced and Skip-level hierarchy.
It also supports time dimension to provide special functionality for modelling time series data.
Parent-child: A parent-child hierarchy is a hierarchy in a standard dimension that contains a
parent attribute. A parent attribute describes a self-referencing relationship, or self-join, within
a dimension main table. It is actually value-based hierarchy. It consists of values that define the
hierarchy in a parent-child relationship (Figure 2.3).
Example: An employee hierarchy might have no levels but might just contain names of
employees who are managed by other employees. Employees may have titles like Vice President
and then Vice Presidents might report to other Vice Presidents and they can be at different
depths in the hierarchy.
Figure 2.3: Parent-child Hierarchy
Source: http://3d.recoil.org/nojavascript/Images/Parent-Child.gif
In addition to above discussed two level of hierarchy it can be of following type as well:
Ragged Hierarchy: A hierarchy in which all the lowest-level members do not have the same
level of depth is ragged hierarchy.
Example: A time hierarchy might be having current month data at the day level, the
previous month’s data at the month level, and the previous 10 year’s data at the quarter level.
It is also known as an unbalanced hierarchy.
Skip-level: A hierarchy in which certain members do not have values for certain higher levels
are known as skip-level hierarchy.
Example: In India, Delhi city does not belong to another state (it belongs to Delhi as a
state itself).
What matters is that users can still navigate from the country level (India) to Delhi (city level)
and below without the need for a state level.
User-defined: These are user-defined hierarchies of attributes that are used in service of Microsoft
SQL Server to arrange the members of a dimension into hierarchical structures and provide
navigation paths in a form of cube.
For example, the Table 2.2 defines a dimension table for a time dimension.
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