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make a big difference for the sample database, but consider what happens if we add
a new product category to the dimension. If we specify the allowed members for the
role, the new category will not be visible to the role members; on the other hand, if
we include an explicit list of denied members with the role, the new category will be
visible because it won't be part of the denied member set.
Keep in mind that we could define both allowed and denied member sets on the
Ad-
vanced
tab. In this case, SSAS will allow us to browse data for all members included
in the allowed member set except those in the denied member set. To completely
deny access to a hierarchy, include an empty set specified by the
{}
notation in the
allowed member set.
The default member box that you saw while configuring the role can be used to
define the product category that will implicitly be used by any query that does not
include a reference to the category hierarchy. For example, you could set the default
member to
[Product].[Category].&[1]
so that the role members will see the
measures specifically for the
Bikes
category unless their queries explicitly specify
other categories. You normally define the default member for the role if the allowed
member set does not include the hierarchy's default member (visible to roles with full
access to the dimension). For example, if the default member is
All Categories
but
you only want to expose
Bikes
and
Accessories
to a particular role, you could set
the role's default category to
Bikes
.
Now, if you query the cube as a role member and choose
All Products
as the
product category, you will see a different number than what you would see as the
total of
Bikes
and
Accessories
. Although you have accomplished the goal of hid-
ing the
Clothing
and
Components
categories, the role members can become sus-
picious and perhaps even doubt the validity of cube data because the sum of the
categories they see does not add up to the total for all categories. Fortunately, the
visual totals feature is here to help; once you check the
Enable Visual Totals
box
on the
Advanced
tab, SSAS will calculate the aggregate value (in this case, the ag-
gregate will be the sum of
Bikes
and
Accessories
) during query execution instead
of displaying the aggregate value available in the cube that includes all product cat-
egories. Since the value must be calculated during query execution, the visual totals
feature does add a slight performance overhead.
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