Product(maker, model, type)
PC(model, speed, ram, hd, price)
Laptop(model, speed, ram, hd, screen, price)
Find those manufacturers of at least two different computers (PC’s or laptops) with speeds of at least 3.0
is my query correct?
select maker from Product NATURAL JOIN PC where speed>=3 AND count(distinct model)>=2
UNION
select maker from Product NATURAL JOIN Laptop where speed>=3 AND count(distinct model)>=2