select public.warehouse_item_types.title, public.warehouse_item_units.code, 
 public.warehouse_document_operation_entries.amount,public.warehouse_document_operation_entries.price,
 public.warehouse_document_operation_entries.cost,public.vat_rate.value,public.warehouse_document_operation_entries.sum_vat_rate,
 public.warehouse_document_operation_entries.cost_with_vat
from public.warehouse_item_types, public.warehouse_item_units,public.warehouse_document_operation_entries,public.vat_rate
where public.warehouse_item_types.id in 
(select public.warehouse_operation_entries.warehouse_item_type_id
from public.warehouse_operation_entries 
where public.warehouse_operation_entries.warehouse_operation_id in 
(select public.warehouse_outgoing_goods_waybill.warehouse_operation_id 
from public.warehouse_outgoing_goods_waybill 
where public.warehouse_outgoing_goods_waybill.id = 493)) 
and public.warehouse_item_units.id = public.warehouse_item_types.units_id
and public.warehouse_document_operation_entries.warehouse_item_type_id = public.warehouse_item_types.id 
and public.vat_rate.id = public.warehouse_document_operation_entries.vat_rate_id 

beforeOpen

var  a = new Array;
a=getParameter(params["dateInvoice"]);
while(a.iter.hasNext){
row["dateInvoice"]=iter.next();
}

beforeOpen
maximoDataset = MXReportDataSetProvaider.create(this.getDataSource().getName(),this.getName());
maximoDataset.open();
var sqlText = new String();
sqlText = "select public.warehouse_item_types.title " +
"from public.warehouse_item_types"+
"where public.warehouse_item_types.id "+
" in (select public.warehouse_operation_entries.warehouse_item_type_id"+
" from public.warehouse_operation_entries "+
" where public.warehouse_operation_entries.warehouse_operation_id in "+
" (select public.warehouse_outgoing_goods_waybill.warehouse_operation_id " +
"from public.warehouse_outgoing_goods_waybill where public.warehouse_outgoing_goods_waybill.id = 455 )) ";
maximoDataSet.setQuery(sqlText);

onFetch
if(!maximoDataset.fetch()){
return (false);
}
row["title"]=maximoDataset.getString("title");
return(true);

 Long warehouseEntryId =  em.createQuery("SELECT w.operation.id FROM WarehouseOutgoingGoodsWaybill AS w WHERE w.id =:id", Long.class).setParameter("id",id).getSingleResult();
        List<String> itemTitle = em.createQuery("SELECT i.itemType.title FROM WarehouseOperationEntry AS i WHERE i.warehouseOperation.id=:warehouseEntryId", String.class).setParameter("warehouseEntryId",warehouseEntryId).getResultList();
        root.put("warehouseOperationId", warehouseEntryId);
        root.put("docId", id);
        root.put("itemTitle", itemTitle);

task.setParameterValue("itemTitle", objectMap.get("itemTitle"));

Никаких новых датасетов создавать не надо.
Сам датасет, конечно же, должен быть типа SQL Select Query.

columnTotal = 0;

columnTotal = columnTotal + row["Aggregation"];