Advanced Cube Design - Professional SQL Server Analysis Services 2005 with MDX - page 386

children of the current member of the time dimension. That is, if the current
member is a month member, then the average rate is calculated by averaging
the Average Rate measure for all days in that month.
You can best see the effect of Average Rate on Internet Sales Amount by
browsing the cube. Place Destination Currency on rows, and add the meas-
ures Average Rate and Internet Sales Amount as shown in Figure 9-4 .
Figure 9-4
In Figure 9-4 you can see the U.S. dollar is the base currency because it has
an Average Rate of 1. Please note that the Internet Sales Amount for the oth-
er currencies is not derived from the division of Internet Sales Amount shown
in U.S. dollars by the destination currency's Average Rate. The MeasureEx-
pression defined for Internet Sales Amount causes Analysis Services to cal-
culate a value for each individual transaction, dividing Internet Sales Amount
in US dollars by the Average Rate for that day, and then aggregating the cal-
culated values to show the Internet Sales amount in the desired currency.
(You'll learn later in this chapter how the individual transactions were conver-
ted to US dollars before the MeasureExpression is applied.) Incidentally, be-
cause the FormatString property for Internet Sales Amount is set to Currency,
all values for this measure are shown as dollars in the browser. Ideally, you
should use an MDX expression for this property to format the value based on
the user's selected destination currency.
Once you have a measure group and its measures designed just right, you
can add that measure group into another cube. If you are familiar with Analys-