union

select id, total_amt, applied_amount, bill_type, balance, bill_headers.partner_id, gross from
(
	(SELECT (sum(sd_headers.vatable_sales) + sum(sd_headers.vat_exempt) + sum(sd_headers.zero_rated) + sum(sd_headers.none) ) as gross,
									sum(sd_headers.vat_amount) as so_vat_amount,  sd_headers.partner_id as partner_id
									from bill_sub_details LEFT OUTER JOIN sd_headers on bill_sub_details.dr_id = sd_headers.id) 
UNION ALL 
	(SELECT (sum(project_headers.vatable_sales) + sum(project_headers.vat_exempt) + sum(project_headers.zero_rated) + sum(project_headers.none) ) as gross,
							sum(project_headers.vat_amount) as proj_vat_amount, project_headers.partner_id as partner_id
							from bill_details LEFT OUTER JOIN project_headers on bill_details.ref_no = project_headers.id)
) as sales 
right JOIN	bill_headers on bill_headers.partner_id = sales.partner_id
where bill_headers.partner_id = 5 and balance > 0 and status in ('Approved','Printed')