If you want to do this without using loops in the orchestration, maybe because you want straight through messaging, you will need to process the message parts into a single message in a pipeline. You will need a 3 level xml structure rather than the default sql adapter 2 level structure, something like the xml below
<QuerySet><Query><QueryResult/></Query></QuerySet>
While the message parts are parts of a message, they are in fact seperate xml documents, and as such can not be accessed using standard message processing (maps, dot notation and the like).
I have done this with loops, and also found a useful blog, but I have lost the link that gave the example. I can try and post the example if it will be of use