Database Reference
In-Depth Information
Figure 9-40.
Selecting related tables for the dimension
Select Dimension Attributes
Dimensional tables commonly have many columns in addition to their key and name columns. In the example,
we are using additional columns, such as title type, title price, and publisher name.
Each of these columns of data is copied to SSAS to form additional dimensional attributes. Remember that
a dimensional attribute is a copy of data from one or more columns in a data warehouse table. For example, you
may note that the TitleName does not show up in the list displayed in Figure
9-41
, even though the Title Key
attribute does. This is because the Title Key attribute represents both the title name and the title key columns in
the data warehouse.
Later when you query the data from the SSAS dimension, you are able to specify whether the TitleKey
attribute will display either the key value or the name value. From this example, you can see that a dimensional
attribute is not the same as a tables column but rather a logical representation of one or more columns of data.
Keep in mind that many dimensional attributes represent only one column within the data warehouse table
(that is, the key and name columns are the same). The dimension key is the most common exception, but date
columns are another. For example, our DimDates table includes columns for Month and MonthName, which will
form a single attribute called Month (Figure
9-41
).
On the Select Dimension Attributes page, you can choose to select all or some of the available attributes.
By default, all attributes are included, but you may want to uncheck the checkbox to exclude them when the
occasion calls for it. You can also change the selections, exclusions, and other options by using the dimension
designer after completing the wizard.
We will configure DateName, MonthName, QuarterName, and YearName as the name columns of DateKey,
Month, Quarter, and Year. Therefore, we will not select these as available attributes (Figure
9-41
).
