Fact Dimension Modeling Question

Question

Hello everybody,

I try to understand dimensional modeling deeply, and work on some cases. Here is my case;

I have an oltp table; which have many measure columns and attribute columns together. For dimensional modeling, I know that each attribute column should correspond to one dimension table. For ex: TYPE column corresponds to D_TYPE etc.

However, for some attribute columns, I can not find a dimension table. That is, a columns includes time value in miliseconds (log data) and I have no time dimension in miliseconds. For this case, what can I do? Should I put that value in fact table? Or, should I create a new dimension table includes miliseconds value? :S

Can you help me please.

Regards,

Dilek

dilek · Answer

Thank you Gianni

Gianni Ceresa · Answer

Hi Dilek,

dileraco wrote:I know that each attribute column should correspond to one dimension table.

I disagree with this one ...

Fact table must contains only measures, attributes must go into dimensions but I wouldn't really say that each column is supposed to be a dimension.

You can also have a kind of generic dimension named "attributes" or "other" where you put attributes not having a dimension, not having a hierarchy (so having just 1 level of data).

But don't leave any attribute in the logical fact table or you end up having issues when having multi-fact needs (as content levels on the fact table will not be the right one for the attribute etc.).

So make them as degenerated dimension (one or many it's up to you ...).