what do you think about this 'full outer join'. Is it ok, or wasting time?
tbl_products owns all product ids.
(select distinct id from tbl_products) as root
vw_report_0_sub0 a on a.id=root.id
vw_report_0_sub1 b on b.id=root.id
vw_report_0_sub2 c on c.id=root.id
vw_report_0_sub3 d on d.id=root.id
where not (a.id is null and b.id is null and c.id is null and d.id is null)