Are attributes of a dimension in hierarchical order?

Question

Do the different 'attributes' of a dimension of an OLAP cube have to have a hierarchical order? If not, would the corresponding cube store the results for each possible combination of the dimension attributes?

Let us assume a cube with only two dimensions: time and product.

• Time (year, quarter, month, day)
• Product (product channel [direct vs. indirect], product group)

While the attributes (how are these called technically?) of the dimension time are clearly strictly hierarchical, the two attributes of the product dimensions are not. We may combine either Channel-Product group or Product group-channel (depending on which one's first).

Is such dimension even possible (non-hierarchical)? If so, which aggregations would the cube store? Each combination (aggregation where first grouped according to channel, then according to product group and the other way around)?

Answer 1

I think Attributes is a perfectly fine name for them - I knew exactly what you meant.

Dimensions don't have to be hierarchical, and very often aren't.

As to which aggregations it will store, there is no simple answer. It will depend on what DBMS you are using, and what you tell it to do. For example with SQL Server (SSAS) you can tell it to precalculate a given percentage of results, from 0 to 100. However within that you can't tell it which ones: it'll do that itself; you can only tell it e.g. 50%. I usually specify 100%.

Other DBMS's will have different facilities.