IBM Cognos, Руководство пользователя

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Track Monthly Performance Measures in Different Time
Periods
Business users often want to see monthly performance in one time period
compared to another. You can add the extra time dimension to your model by
using the calculated columns feature. This solution doesn't require a change to the
date columns in your source data.
For example, you can use a calculated column to model monthly sales revenues,
comparing the performance in 2006 to that in 2007. Your users can see a graphic
representation of their results in their OLAP reporting component.
Procedure
1. Add a calculated column to your model.
For more information, see “Define a Calculated Column” on page 59.
2. When prompted to select a data class for your calculated column in the
Column Data Class dialog box, select Numeric and click OK .
3. In the Column Calculation dialog box, enter the following formula:
month(<Date>)
where
<Date>
is the column used to build your time dimension.
4. Click OK twice.
The newly created calculated column appears as a new column in the data
source.
5.
Drag the new calculated column from the
Data Sources
list to the
Dimension
Map
to create a new dimension.
6. Add the required levels, dimensions, and measures to your model and create
the cube.
For more information about creating cubes, see “Create a Single PowerCube”
on page 123.
Setting up Special Categories
A special category groups regular categories from any level in a dimension,
without regard for their normal hierarchical organization. Special categories are
unstructured and, unlike the categories in an alternate drill-down path, they must
be maintained manually. However, your OLAP reporting component can be set up
to show these categories in all drill-down lists, below the regular categories in the
same dimension.
Note: In IBM Cognos, special categories are often considered alternate hierarchies
within the same dimension.
By default, measure values are summarized. However, you can manually disable
the rollup option.
If a cube is based on an apexed view, whether directly or indirectly by means of a
cube group, the special categories become children of the apexed category.
Create a New Special Category
To highlight important data in the model, you can create special categories.
In the Categories diagram, the children of the special category appear both in the
main hierarchy and in the special category branch. Any changes to a regular
category within this group are reflected in both instances.
Chapter 4. Structuring Your Data Into Dimensions
85