select avg(price) price
from pc a,product b
where a.model = b.model and b.make = 'd';select avg(price) price
from laptop a,product b
where a.model = b.model and b.make = 'd';
from pc a,product b
where a.model = b.model and b.make = 'd';select avg(price) price
from laptop a,product b
where a.model = b.model and b.make = 'd';
select avg(price) price
from
(select price
from pc a,product b
where a.model = b.model and b.make = 'd'
union all
select price
from laptop a,product b
where a.model = b.model and b.make = 'd') as T
Select avg(price) price
from product a,pc b
where a.model=b.model and a.make='d'
union all
(select avg(price)
from product a,laptop l
where a.model=l.model and a.make='d'
)