select id,case PremiumInfoID when null then CategoryID else PremiumInfoID end from Members where id=@MemberID

select id,case PremiumInfoID when null then c.Name else pc.Name end 
from Members as m
left outer join Categoryes as c on c.CategoryID=m.CategoryID
left outer join PremiumCategoryes as pc on pc.ID=m.PremiumInfoID 
where id=@MemberID

select id,case PremiumInfoID when null then c.Name else pc.Name end 
from Members as m
left outer join Categoryes as c on c.CategoryID=m.CategoryID
left outer join PremiumInfo as pi on pi.ID=m.PremiumInfoID
left outer join PremiumCategoryes as pc on pc.ID=pi.PremiumCategoryes where id=@MemberID