[rsAggregateOfMixedDataTypes] The Value expression for ‘x’ uses an aggregate function on data of varying data types. Aggregate functions other than First, Last, Previous, Count, and CountDistinct can only aggregate data of a single data type
Yet another irritating error message from reporting services
You will typically get that error, when you try to create a calculated member in the visual designer like so:
IIF( [Measures].[x]=0 , [Measures].[y] , 0,00)
And then use the SUM or another aggregate function on the new measure.
If you create the same calculated member in pure MDX, [...]