select ให้แสดงออกมาตามกลุ่ม เหมือนกับเป็นการ sort by ซ้อนกัน 2 รอบ ทำยังไงคะ

$sSql_detail = "select *
					from 
						tbl_spt_req,
						tbl_spt_req_detail,
						tbl_spt_itemGroupType,
						tbl_spt_productTiles
					where
						tbl_spt_req.request_no = $txtRequestNo and
						tbl_spt_req.request_no = tbl_spt_req_detail.request_no and
						tbl_spt_itemGroupType.itemGroupType_no = tbl_spt_req_detail.itemGroupType_no and
						tbl_spt_req_detail.material_code = tbl_spt_productTiles.material_code and
						tbl_spt_itemGroupType.itemGroupType_no between 1 and 4 
					ORDER BY 
						tbl_spt_req_detail.itemGroupType_no
					";

for($i = 0; $i <=1; $i++)
{
if($i == 0){
$order = "tbl_spt_req_detail.itemGroupType_no";
}else{
$order = "tbl_spt_req_detail.itemGroupID";
}
$sSql_detail = "select *
					from 
						tbl_spt_req,
						tbl_spt_req_detail,
						tbl_spt_itemGroupType,
						tbl_spt_productTiles
					where
						tbl_spt_req.request_no = $txtRequestNo and
						tbl_spt_req.request_no = tbl_spt_req_detail.request_no and
						tbl_spt_itemGroupType.itemGroupType_no = tbl_spt_req_detail.itemGroupType_no and
						tbl_spt_req_detail.material_code = tbl_spt_productTiles.material_code and
						tbl_spt_itemGroupType.itemGroupType_no between 1 and 4 
					ORDER BY $order";
}