Query Performance and Result Set Query/Sub-Query

Hi,

I have an infoset with as many as <b>15 joins</b> with different ODS and Master Data..<b>The ODS are quite huge with 20 million, 160 million records)...</b>Its taking a lot of time even for a few days and need to get atleast 3 months data in a reasonable amount of time....

Could anyone please tell me whether <b>Sub-Query or Result Set Query have to be written against the same InfoProvider</b> (Cube, Infoset, etc)...or they can be used in queries

on different infoprovider...

Please suggest...Thanks in Advance.

Regards

Anil