Advanced Topics in MDX - Professional SQL Server Analysis Services 2005 with MDX - page 282

They are semantically the same but it is a matter of convenience if say, you
want to create a calculated measure and are not sure about the actual ex-
pression. You can define the calculated member, use it in statements and fi-
nally create the actual expression in the MDX script.
CREATE MEMBER [Profit];
[Measures].[Profit] = [Measures].[Sales Amount] -
[Measures].[Total Product Cost];
Named sets and calculated members are the basic objects created within
MDX scripts most likely to be exploited by users of the cube. You can specify
properties such as format string, font, color, and background color for the cal-
culated members as discussed in Chapter 6 . Next, you see some of the addi-
tional statements that are used within MDX scripts and how they help you
define your business calculations.
Cube Space and Autoexists
The cube space (cells) in an Analysis Services cube can be calculated as the
product of the member count in each attribute from each dimension. As you
can imagine, this space is quite large even for a small cube that contains less
than ten dimensions, with each dimension containing around ten attributes.
The entire cube space is quite large and often the cells that have the data are
quite sparse as compared to the entire space. When we refer to the data in
the cube space we do not just refer to the data in the fact table. You can apply
calculations through MDX expressions to various cells in your cube space.
Most of these calculations are defined within MDX scripts.
Before you learn to specify cell calculations you need to have a better under-
standing of the cube space that comprises all the cells. Some cells in the
cube space retrieve data through calculations or are aggregated up across di-
mensions based on your business definitions within the cube. For example,
consider the budget of your company for next year or the sales quota for next
year, which are typically calculated based on profit or sales of the current
year. This data is not available in the fact table but is likely based on a calcu-
lation of the data in the fact table. Similarly, you can have cell values for which
data is aggregated from fact data due to cube modeling scheme.