selection = new QuerySelection();
selection.addColumn(new AggregationColumn(new SimpleColumn("age"),
AggregationType.SUM));
selection.addColumn(new AggregationColumn(new SimpleColumn("name"),
AggregationType.COUNT));
selection.addColumn(new ScalarFunctionColumn(
Lists.<AbstractColumn>newArrayList(
new SimpleColumn("seniorityStartTime"),
new SimpleColumn("hireDate")), DateDiff.getInstance()));
selection.addColumn(new SimpleColumn("dept"));
q.setSelection(selection);