It is important when specifying your dimensional information to understand the
affect this will have on the SQL that is generated. Dimensional information
affects grouping and aggregation of data, not only from the dimension data
source but also from other data sources that have relationships with that
dimension. Specifying hierarchies for a query subject using query items as
levels, either individual or combinations of query items as keys, and associating
query items to the appropriate levels as attributes provides FM with enough
information to automatically group and aggregate data according to the
hierarchies you have specified. Hierarchies in this case can be thought of as
ways of specifying the order in which data segmented into levels can be
grouped.
