ขอคำปรึกษาการแสดงค่าหลายชั้นของ SQL หน่อยครับ ในคิดคำนวณ

users.id_user = warranty_members.user_id
warranty_members.id_members = warranty_product.member_id
warranty_product.serial = warranty_serials.serial
warranty_product.warranty_no = warranty_serials.warranty_no
warranty_serials.item_code = warranty_items.item_code

select 
	us.username as USERNAME, 
	us.email as EMAIL, 
	wm.name as NAME, 
	count( wp.id ) as PRODUCT,
	sum(coalesce(wi.rrp, 0)) sum_rrp
from users us, 
left join warranty_members wm
	on us.id = wm.user_id
left warranty_product wp 
	on wm.id_members = wp.member_id
left join warranty_serials ws 
	on wp.serial = ws.serial and wp.warranty_no = ws.warranty_no
left join warranty_items wi on ws.item_code = wi.item_code

group by wm.user_id
order by product desc

select
	us.username,
	us.email,
	wm.name,
	count(wr.id) as product,
	sum(coalesce(wi.rrp, 0)) as sum_rrp
from users us
left join warranty_members wm on us.id_user=wm.user_id
left join warranty_product wp on wm.id_member=wp.member_id
left join warranty_serials ws on wp.serial=ws.serial and wp.warranty_no=ws.warranty_no
left join warranty_items wi on ws.item_code=wi.item_code
group by wm.user_id
order by product desc

select 
	us.username,
	us.email,
	wm.name,
	count(wp.id_register) as product,
	sum(coalesce(wi.rrp, 0)) as sum_rrp
from users us, warranty_members wm, warranty_product wp, warranty_serials ws, warranty_items wi
where us.id_user=wm.user_id
and wm.id_member=wp.member_id
and wp.serial=ws.serial
and wp.warranty_no=ws.warranty_no
and ws.item_code=wi.item_code
group by wm.user_id
order by product desc

username   email             name   product   sum_rrp
687549w    [email protected]   Sime   1366      153860.16

username   email             name   product   sum_rrp
687549w    [email protected]   Sime   145       153860.16

select
	us.username, 
	us.email, 
	wm.name, 
	count(distinct wr.id) as product, 
	sum(if(wr.serial_no=ws.serial_no, wi.rrp, 0)) as sum_rrp
from users us
left join warranty_members wm 
	on us.id=wm.user_id
left join warranty_product_registrations wr 
	on wm.id=wr.warranty_member_id
left join warranty_serials ws 
	on wr.serial_no=ws.serial_no 
	and wr.warranty_no=ws.warranty_no
left join warranty_items wi 
	on ws.item_code=wi.item_code
where us.email is not null
	and us.email <> ''
	and wm.name is not null
	and wm.name <> ''
group by wm.user_id
order by product desc

select 
	wr.product_category_name, 
	wr.model, 
	wr.serial_no, 
	wr.warranty_no, 
	if(wr.serial_no=ws.serial_no, wi.rrp, 0) as rrp
from users us
left join warranty_members wm 
	on us.id=wm.user_id
left join warranty_product_registrations wr 
	on wm.id=wr.warranty_member_id
left join warranty_serials ws 
	on wr.serial_no=ws.serial_no 
	and wr.warranty_no=ws.warranty_no
left join warranty_items wi 
	on ws.item_code=wi.item_code
where wm.user_id='381607'
group by wr.id