OLAP vs DMR vs Relational Query behavior

[raj_aries]

Hi All,

I've a question concerning the query behavior for DMR.

Here is my understanding
OLAP query generates cross join when you include members sets from two different hierarchies.
Relational query works as per the joins defined at FM.

How does the query gets processed for DMR? as per my understanding, I've seen that relational retrieves matching records (assuming inner join). However, DMR query retrieves all the members.

since DMR model is built on relational layer a relational query is generated then why is there a difference in the report outputs for Relational Query Vs DMR Query.

[pumccg]

DMR works like a hybrid between relational and OLAP in nested hierarchies. Unlike OLAP, if a child member has a measure value for at least one parent member, then it is returned for all parent members. This is because, at run time, a relational query is processed and the result is returned to build a temporary cube. If there are no returns for a given child member then that member is dropped from the temporary cube. However if a child member has a value for only one parent, it is retrieved and populates the temporary cube, and as a cube then appears for all parents, even though null for all except one parent. Hope this makes sense.

[blom0344]

Afaik (and researched using traces) only the most rudimentary DMR analysis generates 1 relational query. In most cases Cognos generates sets of queries that are recombined. A relational query against a well-formed model generates a single statement (unless deliberate stitch queries are generated)

[raj_aries]

Hi pumccg

I think that makes sense.I'm able to replicate the scenario and it works the way you mentioned.

Unlike OLAP that generates a cross join, DMR drops off the member with no values for any combination. If there is atleast one member then it gets displayed for all the parents.

Thank you so much for enlightening me.

Regards
Raj

[pumccg]

 :)