You can use OQL in a dataset to display data.
What exactly are you trying to do?
Maybe this blog will be of more help.
Sorry I dont have too much experience with OQL.
Can you not accomplish what you want to do with a datagrid and listening widget?
I'm not too sure what you are doing but you can show associated data this way. I used a datagrid on the left and a listening widget with a datagrid over association inside of it. Now when I select a row from the grid on the left, the right grid will show the associated data.
I created a small test. Here is the Group/Details data:
and here is a sample page that displays the data grouped with subtotals:
I used the following domain model for this example
and the page that shows detail grouping with subtotals looks like this:
I calculated the group totals in a microflow.
Maybe this example will give you some ideas about how to do what you need to.
How to populate group totals