I second Gabrielle's suggestion...
Note: 1147419 Consulting note: Unrequired Aggregation during extraction
This note contains instructions on how to avoid GROUP BY on specific DTPs. (The RSDRI_READ_WITH_GROUP_BY = NONE works globally).
If you are on 7.3 you can avoid this by deactivating aggregation on an individual DTP also...
1536734 - Deactivating aggregation
You could also try/test the followig if you want to avoid group by for particular DTPs => you can maintain the RSADMIN parameter nc_rsadmin_group_extr with value as the DTP technical name.
If the testing of the RSADMIN parameter doesn't suit and you don't want aggregation and you don't want to disable it across the system, then the only option is to follow the instructions of the consulting note 1147419 .
Let us know which option works best for you so other users can refer to this thread,
thanks,
Colm