How to Group by multiple Elements in a .RTF template?

Hi Gurus.

I have following requirement:

consider following select:

select sum(hours), period_end_Date, payment_date, hours_type from labor_table
group by period_end_Date, payment_date, hours_type;

How can I achieve above select result in .rtf template.

It only allows me to group by one element/column.
<?for-each-group:Run_Result_Rec;./PERIOD_END_DATE?><?sort:LAST_NAME;'ascending';'text'?>

If I put something like following in the next loop, its not working. Meaning, it is only resulting rows at PERIOD_END_DATE level.

<?for-each-group:current-group();./PAYMENT_DATE?>

How do I achieve this?

Please advise.

Thanks,

Darsh