Mapping measures in a cube vs Calculated Measure

Question

I have a fact table as
Fact_Table_
Sales Product_ID Special_Product_Flag
Special_Product_Flag is a y/n flag
and a Dimension_ table as
Product_ID Product_Name
I want to have 2 measures in the cube
1. Product_Sales
In the cube I specify the mapping for this measure as Fact_Table.Sales
2. Special_Product_Sales
in the cube I specify an olap expression in the mapping as
     case
     when Fact_Table.Special_Product_Flag = 'Y' then Fact_Table.Sales else 0 end
Now is the measure      Special_Product_Sales treated as a calculated measure ?

Answer 1

Here are definitions of base versus calculated measures.
<li> A base measure is a measure that has associated physical storage in the AW. This physical storage is populated using some kind of load step, which may use either SQL or OLAP DML. The measure may then be aggregated according to the aggregation rules of the cube. The value of a base measure for any given cell in the cube may be stored or may be calculated dynamically depending on the "precomputation" rules of the cube.
<li> A calculated measure is one that has no physical storage in the AW. The values of a calculated measure are always calculated dynamically regardless of the precomputation rules of the cube.
Your case is clearly a base measure because you are physically loading data into the AW. The fact that you use a case expression in the mapping does not change the fact that is takes up physical storage nor the fact that it can be aggregated. It is the ability to aggregate the data that makes this a useful feature. In your case you will be able to aggregate special_product_sales up the product hierarchy so that its value for 'ALL_PRODUCTS' will be
select sum(sales)
from fact_table
where Special_Product_Flag = 'Y'The value of sales for 'ALL_PRODUCTS', by contrast, would be
select sum(sales)
from fact_tableAs a side note it may be better to define your mapping using NULL instead of 0.
case
when Fact_Table.Special_Product_Flag = 'Y'
then Fact_Table.Sales
else null
end